CCNet 132/2001 - 10 December 2001

"On several occasions, I and other critics of the IAU guidelines
have requested that the 72-hour review should not take place (for a
Torino nonzero object) until the current observations have ended (at
which point it may not be necessary, of course). At the same time, I have
pointed out that the IAU should not issue any public statement about impact
probabilities that are prone to change due to additional data coming in. It
is time that the IAU WGNEO complies with its assurance that the defective
guidelines will be revised effectively. No more excuses, please."
--Benny J Peiser, 10 December 2001

    Jacqueline Mitton <>

    Benny J Peiser <>

    David Morrison  < >

    NASA Science News, 7 December 2001

    Ron Baalke <>

    Michael Paine <>

   Andrew Yee <>

    Andrew Yee <>

    BBC Online News, 10 December 2001

     Michael Paine <>

     Göran Johansson <>

     Bruce Lerro <>

     John Twigg <j.twigg@UCL.AC.UK>

     Ananova, 8 December 2001


>From Jacqueline Mitton <>


Date: 10 December 2001                 Ref. PN 01/32

Issued by: Dr Jacqueline Mitton (RAS Press Officer)
Phone: +44 ((0)1223) 564914
Mobile phone on meeting day: 07770 386133
Fax:   +44 ((0)1223) 572892

RAS web:

Contacts for this release:

Dr Duncan Steel (University of Salford)
Phone: 0161 295 3981
Mobile phone on 13 and 14 December: 07967 949 342

Professor Mark Bailey (Armagh Observatory)
Phone: 028 3752 2928
Mobile phone on 13 and 14 December: 07765 256 346


Action being taken by the UK government, the United Nations and the European
Space Agency to further our understanding of the hazard posed by near Earth
objects (NEOs) in space are on the agenda at Royal Astronomical Society
meetings in London on Friday 14 December. The meetings are open and media
representatives are cordially invited. (For details of times and locations
see below.)

Dr Colin Hicks, Director of the British National Space Centre, will talk
about the UK government's policy on NEOs. In 2000, the UK government set up
a Task Force to consider the threat from potentially-hazardous NEOs. Its
detailed report (available on-line at
made 14 recommendations for government action.

Dr Hans Haubold, Director of the UN Office for Outer Space Affairs in
Vienna, will discuss the past and future involvement of the United Nations.
The NEO hazard is a global problem, requiring international as well as
national responses. The first step is to map the orbits of the larger
asteroids in the solar system. This can be done using quite modest
telescopes, so smaller countries can make vital contributions.

Dr Marcello Coradini, Coordinator of Solar System Missions at the European
Space Agency's headquarters in Paris, will explain ESA¹s plans for space
missions to study the physical nature of asteroids and comets. NASA already
has several such spacecraft either on the way or planned for launch within
the next few years. ESA's Rosetta mission, the first designed to go into
orbit around a comet, is scheduled for launch in 2003.

Other contributors will describe how UK astronomers and space researchers
plan to become involved with the international Spaceguard programme, how the
NEO impact hazard ranks against other large-scale potential disasters (such
as nuclear power station accidents), and how the media deal with this topic.

Meeting co-organiser, Dr Duncan Steel said, " This is astronomy 'close to
home'. Only recently has the importance of comets and asteroids to our own
planet been recognised. But quite apart from potential impact catastrophes,
NEOs are worlds in their own right. Studying them is becoming a central
feature of solar system exploration. The next few years promise a wealth of
interesting information on asteroids and comets."


HOUSE, Piccadilly, London W1

10:30   Introductory comments and overview: Duncan Steel

10:45   Alan Fitzsimmons (Queen's University, Belfast)
        Observing NEOs with UK-supported ground-based telescopes

11:10   Peter Wheatley  (University of Leicester)
        NEOs in the UK Wide-field Automated Survey Programe (WASP)

11:25   John Zarnecki   (Open University)
        NEO-related Research at the Open University

11:45   Sarah Dunkin  (Rutherford Appleton Laboratory)
        Inner-Earth NEO searches using BepiColombo

12:00   Wyn Evans   (University of Oxford)
        GAIA: A Census of the Solar System

12:20   Phil Palmer  (University of Surrey)
        Research at Surrey University for a NEO mission: Affordable Access
for Science in Space

12:40   Apostolos Christou    (Armagh Observatory)
        Nearer than the Moon: dynamics and future opportunities for NEO

13:00 - 14:00 Lunch break

14:00   Nigel Holloway   (Spaceguard UK)
        NEO Impacts: Risk Perceptions and Realities

14:20   Benny Peiser   (Liverpool John Moores University)
        Asteroid Scares: Near-Earth Objects and the Media

14:35   Iain Gilmour   (Open University)
        The ESF-Impact programme: current objectives and future directions

14:55   Colin Hicks    (Director, British National Space Centre)
        Government Policy and Future Plans on NEOs

15:20   Concluding remarks: Mark Bailey

15:30 - 16:00    Break and  CHANGE OF VENUE

16:00 - 18:00 RAS  monthly Astronomy and Geophysics meeting at the
New Burlington Place)

approx. 17.15 Hans Haubold (Director, UN Office for Outer Space Affairs,
    United Nations Initiatives on NEOs

approx. 17. 35 Marcello Coradini (Coordinator, Solar System Missions, ESA)
   ESA's contribution to the understanding of NEOs and
their related problems


For comment, general information about the meetings, or to get in touch with
individual speakers, contact the meeting organisers:

Dr Duncan Steel
Joule Physics Laboratory
University of Salford
Greater Manchester, M5 4WT
Phone: 0161 295 3981
Fax:   0161 295 5147
Mobile phone contact for Thursday and Friday: 07967 949 342

Professor Mark Bailey
Armagh Observatory
College Hill
Armagh BT61 9DG,
Phone: 028 3752 2928
Fax:   028 3752 7174
Mobile phone contact for Thursday and Friday: 07765 256 346


>From Benny J Peiser <>

One year ago, on November 3 2000, the IAU and NASA released a statement
which announced that the Earth faced a small risk of being hit by a near
Earth object (2000 SG344) in 2030. The next day NASA and the IAU had to
retract their press announcement because additional observations had
eliminated the risk altogether. The rushed and unnecessary announcement was
due to IAU guidelines which request that a "significant impact risk" (i.e.
NEOs that score 1 or higher on the Torino Scale) should be made public after
72 hours if verified.

The main mistake with the SG344 announcement was in the way information
about essentially correct computations was published prematurely and despite
the knowledge that observers were still searching their files for
pre-discovery data. As a result of the embarrassing fiasco, officials of the
IAU Working Group on NEOs promised that the flawed guidelines would be
revised accordingly so that a repetition of the mistake would be impossible.

After the 344SG debacle, not surprisingly, there was mounting pressure to
make effective changes to the IAU guidelines. After all, the IAU guidelines
foolishly stipulate that "If the consensus of the [IAU] review supports the
conclusion that there is a significant impact risk, the results of this
analysis will be posted on the IAU webpage at for public
access at the same time the information is released by the authors to the

That this procedure is extremely harmful and in need of change is reflected
in a year-old assurance on the IAU website which states that "The procedures
for these reviews are currently under revision. Hence the following
information, while being a correct and complete description of the system
that is now in use, is only to be regarded as temporary and will probably be
updated before the end of March 2001" ("Hazardous NEO Technical Reviews " Yet in spite of these public
assurances, no such revisions have been implemented.

The failure to learn the lessons from the SG344 fiasco (and previous
asteroid scares) and which have caused unnecessary distress to the public
means that we may expect new cases of false alarms at any time. As David
Morrison reports below, another damaging asteroid scare was recently averted
largely due to good luck.

Of course, I am very pleased that asteroid 2001 VK5 was eliminated as a
potential threat before an official announcement was published on the IAU
website. On the other hand, it would appear that the positive outcome is a
result of fortuity rather than wise decision making. In short, I am not
entirely convinced that the handling of the 2001 VK5 peer review was an
"example of the proper functioning of the IAU Technical Review", as David
Morrison claims.

Once again, the crucial quandary points to the notorious 72 hours period
before an official pronouncement is recommended by the IAU guidelines.
Thankfully, the members of the WGNEO decided to turn a blind eye to the IAU
guidelines and decided "to defer any announcement from the IAU until after
the USA Thanksgiving holiday." If the existing IAU guidelines had been
followed, the 72-hour rule would have kicked in, meaning that after the
formal review of impact calculations for 2001 VK5 had confirmed a
significant impact risk, the verification of the risk would have be
published on the IAU website. Some media outlets, most likely, would have
picked up the story and made headlines with it, and a few days later the
same media could have been making fun of astronomers as once again a small
impact probability was reduced to zero by new observations.

With another stoke of good luck, new observations of 2001 VK5 had eliminated
all of the remote impact possibilities before the end of the Thanksgiving
holiday, "and 2001VK5 had dropped back to a category zero in the Torino
impact scale."

Morrison's description of events, I'm afraid to say, sounds almost as if he
intended to issue a public announcement on the IAU website in case 2001 VK5
had remained a Torino 1 object (or higher) after the Thanksgiving holiday.
In short, had 2001 VK5 not been eliminated, we might have ended up with yet
another unnecessary alarm. The likelihood of a VI remaining on level 1 of
the Torino Scale over a number of weeks doesn't seem too unrealistic.
Indeed, the question has to be asked what would have happened if the impact
probability of 2001 VK5 had temporarily increased to level 2 or higher on
the Torino Scale?

On several occasions, I and other critics of the IAU guidelines have
requested that the 72-hour review should not take place (for a Torino
nonzero object) until the current observations have ended (at which point it
may not be necessary, of course). At the same time, I have pointed out that
the IAU should not issue any public statement about the impact probabilities
that are prone to change due to additional data coming in.

Of course, I don't want to be too critical with the IAU technical team who
have done a good job after all. Nevertheless, I think it would be wise not
keep in mind the existing pitfalls of the current IAU guidelines which are
in great need of augmentation. Here are just some recommendations that come
to mind:

1. The IAU should no longer "encourage" researchers to submit Torino Level 1
(and higher) virtual impactors for technical review as long as the object is
observable and thus very likely to be eliminated as a potential threat by
additional data.

2. Virtual impactors should only be submitted for review once it is clear
that no new data will eliminate the risk, or no new data is obtainable.
3. If virtual impactors are submitted for review, the review team should
request time for further observational data to be obtained before making any

4. The Torino Scale should no longer be used as a yardstick for deciding
whether not not to go public.

It is time that the IAU WGNEO complies with its assurance that the defective
guidelines will be revised effectively. No more excuses, please.

Benny J Peiser


>From David Morrison  < >

NEO News (12/07/01) 2001VK5 and DPS/AAS


I would like to report briefly on some recent actions of the International
Astronomical Union Working Group on NEOs concerning the new NEA 2001VK5,
discovered on 11 November 2001 and initially announced through Minor Planet
Electronic Circular 2001-V49. This example illustrates the operations of the
IAU technical review process as well as the generally excellent cooperation
of NEA observers and theorists in dealing with a new asteroid that initially
appears to be on an orbit that could lead to a subsequent impact with the
Earth. The great majority of such cases, of course, will turn out to pose no
threat as additional observations become available. This is such an example.

Andrea Milani and his team in Pisa calculated an orbit for VK5 and noted
that the initial results with such a short arc yielded an enormous number of
"Virtual Impactors (VIs)"; their algorithms detected more than 1,000
separate impact pathways, for impacts between 2002 and 2080. The list was
made progressively available on the web, as their computers were producing
the output, starting on 14/11/2001; in the same day the SGF Central Node
launched a "new campaign" to ensure adequate followup. This object was
reobserved on 16/11/2001. By the late hours of 17/11, Milani had calculated
a new list of VIs, with fewer individual impactors but with more significant
probabilities, including a November 2011 Virtual Impactor had a probability
(computed with uniform probability density) of 4.6e-7. This object was of
estimated H magnitude 17.6 and with an average impact velocity could
generate an explosion with energy greater than 100,000 MT. This corresponded
to a value on the Palermo technical scale of -1.85, already a noteworthy
value. Moreover, there were another 14 VIs identified with possible impacts
between 2014 and 2056. At about the same time Steve Chesley reported that
the JPL Sentry automatic collision monitoring system, which is in continuing
development, also autonomously detected the impacting solutions of VK5
reported by Milani. This NEA was in the Category 1 class on both the Torino
Scale and the Palermo Scale, although everyone recognized that these
calculations were based on a short arc, and that new astrometry would almost
surely resolve the uncertainties within a few days.

Milani requested that the WGNEO activate its technical review process for
2001VK5, which I did on 19 November, writing "I concur with your decision to
submit this information to the IAU WGNEO Technical Committee for review at
this time, since it has such a complicated orbit that it is especially
important to obtain independent verification of the virtual impactor
possibilities. In the meantime the asteroid remains visible in a dark sky,
and I have no doubt that additional data will be coming in. This parallel
request for both new observational data and a peer check of the calculations
is in my opinion entirely appropriate. Depending on the events of the next
72 hours the IAU may (or may not) wish to make a formal statement . . . I
personally urge that this be kept as low-key as possible until additional
data are acquired that may resolve the risk of impact."

The members of the IAU Technical Review Team (Don Yeomans, Paul Chodas,
Steve Chesley, Karri Muinonen, Giovanni Valsecchi) did an excellent job of
providing independent analysis of the orbit, confirming (using different
methods) Milani's calculations of the probability of impact. At the same
time, with the active cooperation of both the Minor Planet Center (Brian
Marsden) and the Spaceguard Foundation Central Node (Andrea Carusi),
additional observations were obtained and given immediately to the orbit
calculators. By 21 November (the end of the 72 hour period for the IAU
Technical Review), the possibility of an impact in 2011 had been eliminated
by new data, but there still remained several VIs in the out years. In view
of the continuing input of data, we decided to defer any announcement from
the IAU until after the USA Thanksgiving holiday. Milani posted the current
information on his website but also did not make any public announcement.

By 25 November, orbit calculations based on new observations had effectively
eliminated all of the virtual impactor possibilities, and 2001VK5 had
dropped back to a category zero in the Torino impact scale.

I believe that this case is an example of the proper functioning of the IAU
Technical Review of orbital calculations and of the efforts of the MPC and
SGF to solicit and coordinate additional observations of a high-priority
target. The fact that this international collaboration was carried out
without publicity provides a model for future cases of short-arc NEAs that
are initially flagged as potential impactors but that drop back into the
background as more observations are accumulated. I expect there will be many
more such examples as new NEAs continue to be discovered at a high rate.

David Morrison



Several interesting research results dealing with NEOs were presented at the
33rd meeting of the Division for Planetary Sciences (DPS) of the American
Astronomical Society (AAS), held in New Orleans at the end of November.
Following are a few highlights that seemed interesting to me. The material
presented below is a combination of the published abstract and some
introductory comments that I have added.

David Morrison


The following four abstracts describe results from the successful flyby of
Comet Borrelly by the NASA Deep Space 1 spacecraft. The imaging at
resolutions as good as 60 meters provides the best look at a comet nucleus
since the Giotto photos of Comet Halley. In fact, a combination of higher
resolution and lower dust opacity means that both the surface of the comet
and its focused gas jets are seen better than for any previous comet. The
nucleus is 5 km long and substantially elongated, with a rotation period of
25 hours. Its albedo (reflectivity) is extremely low, about 3%, similar to
dark charcoal or coal. The surface is relatively smooth but shows variations
in albedo.


[26.01] The Deep Space One Encounter with the Comet Borrelly

R. M. Nelson, M. D. Rayman, P. Varghese, D. H. Lehman (Jet Propulsion

On September 22, 2001 NASA's Deep Space One spacecraft flew by the Comet
Borrelly at a distance of 2200 km. The spacecraft instrument package
included a Miniature Integrated Camera Spectrometer (MICAS), a Plasma
Experiment for Planetary Exploration (PEPE), and numerous diagnostic
instruments, intended to monitor the status of ion drive which propelled the
spacecraft (IDS). All the instruments returned high quality science data on
the Comet. This session will present the first results from the flyby to the
scientific community.


[26.02] Observations of Comet 19P/Borrelly from the Miniature Integrated
Camera and
Spectrometer (MICAS) aboard Deep Space 1 (DS1)

L. A. Soderblom (USGS), D. C. Boice (SwRI), D. T. Britt (U Tenn), R. H.
Brown (U Az), B. J. Buratti, M. D. Hicks, R. M. Nelson (JPL), J. Oberst
(DLR), B. R. Sandel (U Az), S. A. Stern (SwRI), N. Thomas (MPAE), R. V.
Yelle (NAU)

Images from the DS1 MICAS CCD camera reveal in three dimensions, the complex
characteristics of Borrelly's nucleus, coma, and jets. The images acquired
during the last 2 hours of the approach, as the nucleus became resolved and
grew to roughly 150 pixels in length, provide stereo coverage of both the
nucleus and inner coma over a wide range of phase angle and exposure time.
The principal structure in the coma is a sunward-pointed collimated jet that
is also visible in ground-based images. This jet is canted about 30 degrees
off the sun line and appears to be roughly aligned with the local vertical
at the surface from where it originates. Long-exposure images reveal details
of the structure of the inner coma. They show the jet, visible at long
range, to be composed of at least three discrete components whose locations
evidently correspond to specific surface features. The elongated nucleus
exhibits topographically distinct terrains and strong albedo variegations
(of at least a factor of 2). The jets emanate from within the brighter
smoother rolling plains. A consistent model is that the main jets are
co-aligned with the rotation axis of the nucleus and issue from regions on
the plains that are currently in constant sunlight. The other major terrain
is a rough unit that is darker than the average, includes even darker
isolated spots, and appears as a jumbled topography. Other surface features
include parallel ridges, crater-like depressions, numerous narrow dark
fracture-like features, and areas of mottled albedo. However no small fresh
impact craters are evident attesting to a geologically young, actively
evolving surface.


[28.03] The Geology of Comet 19P/Borrelly

D. T. Britt (University of Tennessee), D. C. Boice (SwRI), R. M. Nelson
(JPL), L. A. Soderblom (USGS), N. Thomas (MPAE)

The Deep Space One spacecraft returned MICAS images of the Comet
19P/Borrelly with surface resolutions as good as 60 meters per pixel. These
data converted the nucleus of Borrelly from an astronomical object, obscured
by its coma of gas and dust, to a geological object with striking surface
morphology and processes. The surface is dominated by two major units. The
Smooth Rolling Plains (SRP) unit shows higher than average albedo, is
smoother than average, and is associated with the surface locations of
Borrelly's active jets. The smooth terrain and higher albedo appear
associated with active resurfacing processes from dust ejection. Away from
the active jets the surface is darker, rougher, and exhibits mottled albedo
features. This Rugged Terrain unit may represent older surface material.
Along the terminator there are 4 parallel ridges that are oriented normal to
the long axis of the comet. On the sun side are a complex set of fractures
near what appears the narrowest part of the comet. Several crater-like
depressions are visible, but the surface generally lacks abundant craters.
Albedo values vary by at least a factor of two across the surface.


[28.04] Photometry and Surface Physical Properties of Comet 19P/Borrelly

B. J. Buratti (JPL), L. A. Soderblom (USGS), D. T. Britt (U. Tenn.), M. D.
Hicks (JPL), N. Thomas (Max Planck Inst. ), J. Oberst (DLR), R. H. Brown (U.
Ariz.), R. M. Nelson, J. A. Mosher (JPL), J. K. Hillier (Grays Harbor

The successful Deep Space 1 flyby of Comet P/19 Borrelly offers an
unprecedented opportunity to perform disk-resolved photometry and
photometric modeling of a comet's nucleus. The flyby occurred at a favorable
ground-based apparition, enabling concomitant telescopic observations that
provided both the "big picture" in time and space and observations at
photometric viewing geometries not attained by the spacecraft. The solar
phase angle of the encounter period changed from 87 to 52 degrees over a
period of 1.5 hours; this range is ideal for determining the macroscopic
roughness of the comet's surface. The microphysical texture of the surface
is best determined by ground based observations at aphelion and near
opposition. The combination of both disk resolved measurements from DS1 and
disk integrated measurements from both DS1 and the ground permits a
constrained set of photometric parameters to be derived. Preliminary
analysis of the global geometric albedo yields a value at V wavelengths (550
nm) between 0.031 +/- 0.005 (for a Mathilde-type solar phase curve at phase
angles less than 10 degrees) and 0.042 +/- 0.005 (for an average C-type
phase curve). Albedo variegations of at least a factor of two exist on
Borrelly's surface: Its light curve amplitude of nearly a magnitude may thus
not be due to shape alone. The image resolution of ~ 60 m allows mapping of
albedo variegations in terms of active jet morphology.


The following two papers deal with the NASA NEO Program Office and with new
software that can provide an automated search for future impact
possibilities for NEAs.


[41.07] NASA's Near-Earth Object Program Office

D.K. Yeomans, R.C. Baalke, A.B. Chamberlin, S.R. Chesley, P.W. Chodas, J.D.
Giorgini, M.S. Keesey (JPL/Caltech)

In early 1999, NASA established its Near-Earth Object Program Office at the
Jet Propulsion Laboratory, with the stated objectives to: · Facilitate
communications within the observing community and between the community and
the public with respect to any potentially hazardous objects. · Establish
and maintain a catalog of Near-Earth Objects (NEOs) and provide information
on their future close Earth approaches and Earth impact probabilities. ·
Help coordinate ground-based observations in order to complete the
Spaceguard Goal of discovering 90% of the Near-Earth Asteroids (NEAs) larger
than one kilometer within a ten year period. · Support NASA Headquarters in
coordinating with other government agencies and with foreign governments and
international organizations on NEO issues. · Develop and support a strategy
and plan for the scientific exploration of NEOs including their discovery,
recovery, ephemerides, characterization, in-situ investigations, and
resource potential. Significant progress has been made on all of these
objectives. An award winning interactive NEO web site has been established
( to communicate information to the scientific
community and public. An automatic update process (Sentry) has been
established for all NEOs. As new astrometric data become available for a
particular NEO, its orbit is automatically updated and future close Earth
approach circumstances determined - including impact probabilities when
appropriate. At timely intervals, metrics are generated and displayed on the
web site to track the contributions of each NASA supported search site
toward meeting the Spaceguard Goal. Initial efforts to coordinate the
nightly search for NEAs within the United States have been undertaken. In an
effort to facilitate the coordination of NEO activities on an international
scale, fruitful interactions have taken place with personnel of the British
Task Force, the Spaceguard Foundation, the Japanese Spaceguard Foundation
and the international Organization for Economic Cooperation and Development


[41.08] Sentry: An Automated Close Approach Monitoring System for Near-Earth

A.B. Chamberlin, S.R. Chesley, P.W. Chodas, J.D. Giorgini, M.S. Keesey, R.N.
Wimberly, D.K. Yeomans (JPL/Caltech)

In response to international concern about potential asteroid impacts on
Earth, NASA's Near-Earth Object (NEO) Program Office has implemented a new
system called ``Sentry'' to automatically update the orbits of all NEOs on a
daily basis and compute Earth close approaches up to 100 years into the
future. Results are published on our web site ( and
updated orbits and ephemerides made available via the JPL Horizons ephemeris
service ( Sentry collects new and
revised astrometric observations from the Minor Planet Center (MPC) via
their electronic circulars (MPECs) in near real time as well as radar and
optical astrometry sent directly from observers. NEO discoveries and
identifications are detected in MPECs and processed appropriately. In
addition to these daily updates, Sentry synchronizes with each monthly batch
of MPC astrometry and automatically updates all NEO observation files. Daily
and monthly processing of NEO astrometry is managed using a queuing system
which allows for manual intervention of selected NEOs without interfering
with the automatic system. At the heart of Sentry is a fully automatic orbit
determination program which handles outlier rejection and ensures
convergence in the new solution. Updated orbital elements and their
covariances are published via Horizons and our NEO web site, typically
within 24 hours. A new version of Horizons, in development, will allow
computation of ephemeris uncertainties using covariance data. The positions
of NEOs with updated orbits are numerically integrated up to 100 years into
the future and each close approach to any perturbing body in our dynamic
model (all planets, Moon, Ceres, Pallas, Vesta) is recorded. Significant
approaches are flagged for extended analysis including Monte Carlo studies.
Results, such as minimum encounter distances and future Earth impact
probabilities, are published on our NEO web site.


The following paper discusses the internal structure of NEAs and
implications for their break-up during atmospheric entry and impact with the


[41.05] The Role of Asteroid Strength in Impact Damage

J.G. Hills, M.P. Goda (Los Alamos National Lab)

The fragmentation and dispersal of an asteroid in the atmosphere help
determine the damage it can cause (Hills and Goda, 1993, Astronomical J.
105, 1114-1144). Large asteroids are suspected to be rubble piles with
little overall strength. This lack of strength causes them to break up
higher in the atmosphere than would be the case if they had the same
material strength as normal meteorites. The higher elevation breakup causes
them to spread apart more at a given elevation in the atmosphere, so less of
their energy is available for ground impact. We made computer simulations of
such dispersal using asteroids of normal strength and those with much
reduced strength to see if the more fragmented asteroids produce less
damage. We find that these differences are much greater for irons than for
stones, which is not surprising given the greater material strength of the
irons. Irons with radii less than about 20 meters lose most of their energy
before they reach sea level if they are of normal strength. If they are
rubble piles, they produce little ground impact damage unless their radii
exceed 70 meters. Iron asteroids have to have radii above these critical
values to allow them to produce significant craters on land and tsunami in
water. If the radius of an iron asteroids exceeds 200 meters, the size of
the crater it produces is nearly independent of its material strength.
Solid-stone asteroids with radii greater than about 100 meters produce
significant craters. This critical limit is only about 20% larger for
rubble-pile stone asteroids. Blast damage from stony asteroids is not very
sensitive to their strength. Small iron asteroids, with radii less than
about 20 meters, produce more blast damage if they are solid, because their
energy is dissipated lower in the atmosphere. If their radii exceed this
value, the weaker asteroid produces more blast damage than the stronger one
because the stronger one loses less of its energy in the atmosphere and more
of it on ground impact.


One of the most exciting recent areas of asteroid research is derived from
the discovery of asteroid satellites. Observations of a satellite allow
determination of the mass and density of the asteroid, and thus inferences
about its internal structure and composition. The discovery of asteroid
satellites has also stimulated dynamical models to try to understand how
these satellites have formed. Bill Merline of Southwest Research Institute
gave an invited talk on asteroid satellites. It is interesting that small
NEAs as well as larger main belt asteroids have satellites. Four NEA
satellites have been found so far, mostly from radar observations,
suggesting that perhaps 20% have satellites. In addition to the review,
Merline gave the following research paper. Several additional papers (not
included here) dealt with the radar observations.


[52.01] Search for Asteroid Satellites

W.J. Merline (SwRI), L.M. Close (U. Arizona), F. Menard (LAOG, Obs.
Grenoble, France), C. Dumas (JPL), C.R. Chapman, D.C. Slater (SwRI)

We report on the recent progress of our comprehensive search for satellites
of asteroids. In 1998, we began our survey using newly developed
technologies in adaptive optics to explore the close environs of several
hundred main-belt asteroids. Adaptive optics (AO) removes the blurring
caused by the Earth's atmosphere and allows diffraction-limited imaging in
the near-IR (J-,H-,K'-bands) at the world's largest telescopes. Angular
resolutions as high as 0.04 arcsec are possible. We have employed the
excellent facilities at the Canada-France-Hawaii Telescope, the W.M. Keck II
telescope, and the new Gemini North 8m telescope. Each of these facilities
provides unique capabilities and are each complementary to the other. So far
we have discovered or recovered a half-dozen small moons or double asteroids
by this AO-assisted direct-imaging technique. Our sample now exceeds 300
main-belt targets, and we have expanded the survey to include near-Earth and
Trojan asteroids. Other groups are using AO, direct HST imaging, direct
ground-based imaging, advanced lightcurve analysis, and radar techniques to
further sample these populations, as well as the Kuiper Belt. Our results
show that the frequency of binary asteroids (at least to our detection
limits) is rather small in the main belt, possibly a few percent.
Frequencies among other populations, such as the NEAs, are seen to be much
higher. We also find that although there are similarities among the detected
systems, there are also significant differences. Thus, it is likely that
several different formation mechanisms will be required to explain the
observed systems. All of the proposed mechanisms for formation involve
collisions of one type or another (physical or gravitational). Study of
these systems will provide significant insight to the collisional history
and evolution of these asteroid populations. Further, the presence of a
companion allows accurate determination of the density of the primary, and
thus yields vital information about the composition and structure. Already,
we have seen that most asteroids are underdense compared with their likely
meteorite counterparts, and thus we must invoke significant empty space or
macroporosity in their structure.


Several papers discussed the Spaceguard Survey, the population of NEAs, and
the current rate of progress toward meeting the Spaceguard Goal of finding
90% of the NEAs larger than 1 km by 2008. The consensus is growing that
there are roughly 1000 NEAs brighter than absolute magnitude H=18. For a
nominal albedo, H=18 is equivalent to a diameter of 1 km, but this will not
be true for individual objects, depending on their surface reflectivity. The
specific model presented by Morbidelli and his colleagues gives an NEA
population of 834 larger than 1 km and 963 brighter than magnitude 18. It
seems increasingly clear that the current Spaceguard Survey, although it has
by now discovered more than half the NEAs brighter than H=18, does not reach
deep enough (faint enough) to achieve the Spaceguard Goal of 90% discovery
by 2008. For example, the current magnitude limit for LINEAR is about 19,
while the models suggest that it will be necessary to survey down to at
lesst magnitude 20 to achieve this goal. Incidentally, it was reported that
LINEAR has by now effectively surveyed 10 cubic astronomical units for NEAs
down to H=18.


[54.07] Earth and Space-based NEO Survey Simulations: Prospects for
Achieving the Spaceguard Goal

R. Jedicke (Lunar & Planetary Laboratory), A. Morbidelli (Obs. de la Cote
d'Azur), T. Spahr (Smithsonian Astrophysical Observatory), J-M. Petit (Obs.
de la Cote d'Azur), B. Bottke (Southwest Research Institute)

Using our model of the debiased orbital and absolute magnitude distribution
of Near Earth Objects (NEO) (Bottke et al. 2001, Icarus, accepted), we have
simulated the efficiency of various surveying strategies. To check the
fidelity of our model and simulation we have calculated the number of NEOs
with H<18 that the Catalina Sky Survey (CSS) should have detected in a
nine-month observing period. The CSS detected 38 NEOs (2 Atens, 21 Apollos
15 Amors) while we predict that they should have found 28±5 NEOs (1.5±1.2
Atens, 17.3±4.5 Apollos, 9.1±3.3 Amors). Taking into consideration the
difficulties in parameterizing the CSS asteroid rejection system, we believe
our model is reliable and that it can be used to simulate the discovery
efficiency of existing and virtual surveys. Our main results are the
following: (i) the LINEAR-like survey to a limiting magnitude of 18.5 can
not fulfill the NASA goal of finding 90% of NEOs with H<18 by 2008. Only
60-70% of these bodies will be found (current completeness being ~45%). (ii)
the system performance is not much better if restricted to the
sub-categories of NEOs with the largest collision probability with the Earth
or the smallest MOIDs (iii) a LINEAR-like survey with limiting magnitude
~21.5 could fulfill the NASA goal while the proposed LSST survey will be
extremely effective. (iv) the determining factor in a survey's success is
its limiting magnitude. The latitude of the observatory and the `NEO rate
cut' do not significantly reduce the overall performance. (v) a dedicated
survey from a satellite orbiting the Sun from the distance of Mercury would
be extremely effective, especially for discovering NEOs with the smallest
MOID. Even a survey with a limiting magnitude equal to 18.5 would discover
90% of the NEOs in just a few years.


[54.08] Detection Efficiency of LINEAR

J. B. Evans, G. H. Stokes, H. E. M. Viggh, J. S. Stuart (MIT Lincoln

The Lincoln Near Earth Asteroid Research (LINEAR) program has applied
electro-optical technology developed for Air Force Space Surveillance
applications to the problem of discovering Near Earth Asteroids (NEAs) and
comets. LINEAR, which started full operations in March of 1998, has
discovered through July of 2001, 667 NEAs, 35 unusual objects, and 64
comets. Currently, LINEAR is contributing ~70% of the world-wide NEA
discovery rate. This paper details preliminary studies into the detection
efficiency of the LINEAR system. The detection efficiency of the system is
computed for individual nights when the region of sky searched has a
statistically significant number of candidate moving objects for detection.
Limiting visual magnitudes are obtained from these nights, and the
information garnered allows for the estimation of the limiting visual
magnitudes for the remainder of the nights. An accurate measure of the
limiting magnitude is essential to characterizing a search system's


[54.09] The NEA Population and the Spaceguard Goal

J.S. Stuart (MIT)

Three years of search data from the Lincoln Near-Earth Asteroid Research
(LINEAR) project allow us to estimate the size and shape of the near-Earth
asteroid population. To calibrate the limiting magnitude of the LINEAR
search, we restrict ourselves to nights with stable weather. We are left
with 375,000 square degrees of sky coverage and over 1300 NEA detections. A
simulation of discovery circumstances for the range of absolute magnitude
and orbital parameters of the detected asteroids is used to determine the
detection probabilities. From these detection probabilities, the biases of
the survey are estimated, allowing us to calculate the total population from
that which is observed. We previously presented (DPS2000) a population
estimate that used an assumption for the shape of the population over the
semi-major axis and eccentricity dimensions. In this work we remove that
assumption and derive estimates over absolute magnitude (H), semi-major
axis, eccentricity, and inclination. As in the previously presented work, we
find that the NEAs are more highly inclined than the currently known
population and more highly inclined than other estimates. The number of NEAs
with H<18 is found to be in the range 1150 to 1400. We also investigate the
requirements for a search system to complete the Spaceguard goal of
discovering 90% of the 1 km NEAs by 2008, assuming that the real population
is similar to the model derived here. Since the albedo distribution of the
NEAs is currently unknown, we cannot fully evaluate progress toward the
Spaceguard goal. However, if we assume that H=18 corresponds to a diameter
of 1 km, then a single telescope similar to LINEAR requires 40 years to
reach 90% completeness. If the albedo distribution of the asteroids is such
that 1 km corresponds to H=17.5, then 30 years are required. The opposite
case of low average albedo, setting the 1 km target at H=18.5, requires 60
years. A coordinated collection of telescopes capable of searching the
entire available sky each lunation to limiting magnitude V ~ 20.5 is
necessary to complete the Spaceguard goal in 10 years from system inception,
assuming that H=18 corresponds to 1 km.


[54.06] NEO Albedo Distribution and Impact Hazards

A. Morbidelli (Observatory of Nice, France), W.F. Bottke (South West
Research Institute, Boulder, Co.), R. Jedicke (Lunar Planetary Laboratory,
Tucson, Az.), P. Michel (Observatory of Nice, France), E.F. Tedesco
(TerraSystems Inc., Lee, NH)

Our NEO orbital-magnitude distribution model (Bottke et al., 2001, Icarus,
in press) relies on 5 main intermediate sources for the Near Earth Object
population: the nu6 resonance, the 3:1 resonance, the outer portion of the
main belt (I.E., 2.8-3.5 AU), the Mars-crossing population adjacent to the
main belt, and the Jupiter family comet population. The model establishes
the relative contribution of these sources to the NEO population, in each
region of the NEO orbital space. Therefore, by computing the albedo
distribution of the bodies in/close to each source, we can deduce the albedo
distribution of the NEO population, as a function of their orbital location.
An important caveat is that the albedo distribution of main belt asteroids
may change with the absolute magnitude, because asteroid families and
background populations have different albedo and magnitude distributions. In
our model we extrapolate the observed absolute magnitude distributions of
the families up to some threshold value Ht, beyond which we assume that the
families magnitude distribution is background-like. We find that Ht=15
provides the best match to (I) the color vs. heliocentric distance
distribution observed by the SLOAN survey and with (II) the observed albedo
distribution of NEOs. Our model predicts that the debiased ratio between
dark and bright (albedo smaller or larger than 0.089) NEOs with diameter
larger than 1km is 0.8 . We estimate that the total number of NEOs larger
than a kilometer is 834 which, compared to the total number of NEOs with
H<18 (963), shows that the usually assumed conversion H=18~<=>~D=1km is
slightly pessimistic, on average. The right statistical correspondence
should be H=17.82~<=>~D=1km. Combining our orbital distribution model with
the new albedo distribution model, and assuming that the density of bright
and dark bodies is 2.7 and 1.3 g/cm3, respectively, we estimate that the
Earth should undergo a 1000 megatons collision every 64,000 years. The NEOs
discovered so far carry only 18% of this collision probability.


Finally, I note that considerable progress has been made lately in
reconciling telescopic spectra of asteroids with the colors measured in the
laboratory for meteorites. We are beginning to understand the ways in which
exposure to space ("space weathering") changes over time the spectra of
materials on asteroid surfaces.


[59.06] Size Dependence of Near-Earth Asteroid Spectral Properties: A
Comparison with Space Weathering Models

R. P. Binzel (Obs. Paris), S. J. Bus (U. Hawaii), T. H. Burbine (NMNH), L.
E. Malcom (Caltech)

The availability of a self-consistent set of visible wavelength CCD spectra
for more than 1400 asteroids (Bus 1999, Ph. D. Thesis; Bus and Binzel,
submitted) that includes measurements for more than 100 near-Earth objects
(Binzel et al., in preparation), provides the basis for an analysis of size
dependent spectral properties. Near-Earth objects, by virtue of their
proximity, provide the opportunity for spectral measurements of objects at
sizes below 100 m. By analyzing the spectral properties of near-Earth
objects in conjunction with those for > 100 km main-belt asteroids, we have
the ability to identify spectral trends for objects spanning more than 3
orders magnitude in size. Collisional lifetimes of asteroids are
proportional to their size, since larger asteroids are less likely to be
disrupted by collisions. Smaller asteroids have shorter collisional
lifetimes. Thus smaller asteroids have younger ages than large asteroids and
can be expected, on average, to have younger surfaces. Space weathering
models that alter an asteroid's surface over time (e.g. Pieters et al. 2000,
Met. Plan. Sci. 35, 1101; Sasaki et al. 2001, Nature 419, 555) would predict
that smaller asteroids would be the less effected by weathering than larger
objects. In this paper we examine the statistical significance of size
dependent trends in asteroid spectral properties and compare significant
trends in the data with the what is predictable based on space weathering
models. The ability of space weathering models to give results consistent
with the data is a key element in evaluating their validity.

NEO News is an informal compilation of news and opinion dealing with Near
Earth Objects (NEOs) and their impacts.  These opinions are the
responsibility of the individual authors and do not represent the positions
of NASA, the International Astronomical Union, or any other organization.
To subscribe (or unsubscribe) contact  For
additional information, please see the website:
If anyone wishes to copy or redistribute original material from these notes,
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>From NASA Science News, 7 December 2001

What are the Geminid meteors? Scientists aren't sure. Perhaps chips off an
exotic asteroid or dust from an extinct comet. In either case, they'll soon
be here.
Dec. 7, 2001: When the thrilling 2001 Leonid meteor storm finally subsided
last month, many first-time meteor watchers were asking the same question:
"When's the next meteor shower!?"

The answer is "now." Today Earth is entering the outskirts of a dusty debris
cloud shed by a mysterious object named 3200 Phaethon. It's the beginning of
the annual Geminid meteor shower, which peaks this year on Dec. 13th and

The two-week long Geminid shower is barely a trickle at the moment -- only 5
to 10 meteors per hour. But soon it will intensify ten-fold or more.

You can catch the main event beginning just after sunset on Thursday, Dec.

"When the Sun goes down on Thursday," says Bill Cooke of the NASA Marshall
Space Flight Center, "Gemini will be low but rising over the eastern horizon
[as viewed from mid-northern latitudes]. You won't see many meteors then,
but the ones you do will likely be beautiful Earthgrazers" -- that is,
disintegrating meteoroids that fly over the horizon nearly parallel to the
atmosphere. Earthgrazers are long, bright and vivid. A remarkable sight.

"After an hour or so of watching for Earthgrazers, you might want to go back
inside for a few hours and warm up," adds Cooke. Meanwhile, Gemini will
continue to climb higher in the sky. "Around midnight go back outside," he
suggests. "Gemini will lie almost directly overhead. From midnight until
dawn on Friday, Dec. 14th, you could spot as many as 100 shooting stars per

Cooke's suggestions are correct for observers in any time zone of the United
States or Europe.

Nowadays the Geminids are generally regarded as one of the best annual
meteor showers. But it wasn't always so. Before the mid-1800's there were no
Geminids, or at least not enough of them to attract attention. The first
Geminid shower suddenly appeared in 1862, surprising sky watchers who saw 15
or so shooting stars each hour.

Astronomers immediately began looking for a comet. Most meteor showers
result from debris that that boils off a comet when it passes close to the
Sun. When Earth passes through the debris, we see a meteor shower.

For more than a century astronomers searched in vain for the parent of the
Geminids. Finally, in 1983, NASA's Infra-Red Astronomy Satellite (IRAS)
spotted something. It was several-km wide and moved in much the same orbit
as the Geminid meteoroids. Scientists named it 3200 Phaethon.

But rather than solving the puzzle of the Geminids parentage, the IRAS
discovery simply deepened the mystery. Why? Because Phaethon appears to be
an asteroid. Indeed it's cataloged as a potentially-hazardous one that skims
by Earth's orbit only 8 times farther away than the Moon. Asteroids that
spew debris into space like a comet are rare indeed, so astronomers were
more baffled than ever.

This unusual asteroid, known as Elst-Pizarro, briefly sprouted a tail in
1996 after, perhaps, a collision with another object in the asteroid belt.
Is this what happened to 3200 Phaethon long ago? Brian Marsden of the Minor
Planet Center discusses the possibility in a Science@NASA article about last
year's Geminids

Since then many sky watchers have come to regard the Geminids as a "weird"
meteor shower -- the only one caused by an asteroid. But maybe, says Cooke,
it's not so weird after all. "I don't think the Geminids come from an
asteroid. They're cometary ... just like all the other meteor showers. 3200
Phaethon is indeed the parent, but it's an extinct or dormant comet."

According to Cooke, Phaethon probably looked much like other comets many
centuries ago, with a fuzzy head and a glowing dusty tail. But this one was
doomed to rapid extinction by its short-period sungrazing orbit. Every one
and a half years Phaethon plunges sunward from the asteroid belt and swings
by the Sun at a distance of 0.14 astronomical units -- closer even than the
planet Mercury. Such near encounters with the Sun would have cooked
Phaethon, vaporizing its ices and leaving behind a shell of asteroid-like
dust and rock.

Such over-cooked comets may be abundant, says Mike A'Hearn (Univ. of
Maryland), the principal investigator of NASA's Deep Impact mission.
"Dynamical studies suggest that perhaps a few percent to 50% of all
near-Earth objects are dormant or extinct comets masquerading as asteroids."

>From a distance there's no definitive way to tell the two apart. "Both
comets and main belt asteroids are very dark," says Lucy McFadden (Univ. of
Maryland), a member of the Deep Impact science team. "And we don't know of
any robust chemical or spectral signature to absolutely identify a comet's
nucleus." Indeed, she says, "even if we were to fly to Phaethon we might not
be able to tell whether it is an extinct comet" without somehow looking
beneath its crust.

That's exactly what the Deep Impact spacecraft will do to Comet Tempel 1
when it travels there in 2005 and excavates a crater by dropping a 350 kg
impactor onto the comet. A goal of the mission is to learn what the crusts
of comets are made of and what lies beneath them. "Perhaps in a few years we
will feel more confident of the chemical signature of comet nuclei," adds

Meanwhile 3200 Phaethon is likely to remain a puzzle. Are the Geminids
caused by old dust from an extinct comet or chips off an exotic asteroid? No
one knows. But don't let that stop you from heading outdoors on Dec. 13th
and 14th. This is a mystery best pondered under dark skies ... with a flurry
of beautiful Geminids soaring overhead!


>From Ron Baalke <>

Dec. 7, 2001
Kathy Burton

NASA Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-1731 or 604-9000)

AGU Moscone Center press room, San Francisco
(Phone:  415/905-1007, general AGU information)



The latest models of meteors and meteoroid streams, the first science
results from the November Leonid meteor storm and the latest Mars research
will be presented at the fall American Geophysical Union (AGU) meeting Dec.
10 through 14 at the Moscone Convention Center in San Francisco.

Dr. Peter Jenniskens, principal investigator of NASA's Leonid "MAC" mission,
which tracked the meteors, will present the latest data at a special
session, "The 2001 and 2002 Leonid Meteor Storms," at the AGU meeting at
1:30 p.m. PST, Dec. 11 in the Moscone Center's room MC 120. Jenniskens,
together with scientists from the Scripps Institute and Cornell University,
will discuss first results from the last two Leonid meteor events, including
airborne meteor and meteor train observations, comet dust composition, the
fate of organic matter at the time of the origin of life, and the physics
and chemistry of the Earth's upper atmosphere. Approximately 30 NASA Ames
scientists will participate in a wide range of space and planetary science
presentations at the AGU meeting, either as session chairs, invited
speakers, lead authors or 'poster session' presenters.

There will be more than 14 AGU presentations dealing with NASA's latest Mars
research, with discussions ranging from the accuracy of Mars climate models
to what currently is known about the red planet's surface geology. Ames
scientists Dr Robert Haberle and Dr Anthony Colaprete will present work
about Mars' climate on Wednesday and Thursday. The Mars Global Surveyor
(MGS) mission has provided a wealth of new data bearing directly on Mars'
climate. Colaprete, Haberle and others will compare the most recent MGS data
with data from the NASA Ames Mars General Circulation Model at separate
sessions scheduled for Dec. 12 at 8:30 a.m. (MC 308) and 3:30
p.m. PST (MC Hall D) and Dec. 13 at 8:30 a.m. PST (MC Hall D). Ames climate
researcher Dr. Jeffery Hollingsworth will discuss Mars' atmospheric
circulation in the Hellas impact basin, comparing model simulations with
recently acquired MGS data on Dec. 12 at 3:55 p.m. PST in MC 301.

Also on the Mars theme, Ames' Dr. Nathalie Cabrol will present a new paper,
"From Gullies to Glaciers: A Continuum of Evidence Supporting A Recent
Climate Change on Mars," on Dec. 10 at 4:20 p.m. PST in MC 131.  Based on
the recent discovery of pristine martian gullies by the Mars Global
Surveyor, Cabrol will present a continuum of evidence that supports a recent
climate change on Mars, signaling a more recent hydrologically active Mars
than scientists had thought previously.  Her talk is part of the "New
Paradigms for the Water Cycle on Mars I" session that begins at 1:30 p.m.

Conditions on early Earth are another topic well represented by Ames
scientists. Dr. Kevin Zahnle of Ames will deliver two review talks
discussing the earliest atmosphere of the Earth. He will present "Hot Steam,
Hard Rain and Icy Wastes in the Hadean" on Dec. 11 at 8:30 a.m. PST in MC
308 at the 'Follow the Water' session and "The Hadean Atmosphere (When
Impacts Ruled the Earth)" on Dec. 14 at 11:10 a.m. PST in MC 134 in the
'Origin and Early Evolution of the Earth' session.

The 'Follow the Water' session focuses on the search for habitable
environments in the solar system.  It will be co-chaired by Dr. Michael
Meyer, senior scientist for astrobiology in the Office of Space Science at
NASA Headquarters and by Dr. Jack Farmer, principal investigator of the
Arizona State University research team at the NASA Astrobiology Institute.

Ames researchers Dr. Linda Jahnke and Kenneth Cullings will reconstruct the
biomarker record of early Earth in a poster sesion (B22D-0184) at 1:30 p.m
PST on Dec. 11 in MC Hall D.

More information about the AGU fall meeting is available on the Internet at:

For further information about Ames' participation in the AGU, go to the AGU
website and search the 'Meeting at a Glance' section using the researcher's
e-mail address.  You also can use the keyword '' to locate
abstracts and session information.

To arrange interviews at AGU, please contact Harvey Leifert in the AGU Press
Room, MC 111, 415/905-1007. Reporters also may arrange an interview at AGU
by using the AGU message board located outside Moscone's main exhibition

The AGU is a worldwide organization comprising over 39,000 scientists in
Earth and space science, publishing more than a dozen peer-reviewed journals
annually and holding regular science meetings.


>From Michael Paine <>

Dear Benny

There is once again a smorgasbord of NEO-related items at the annual meeting
of the American Geophysical Union

Below is a selection of titles
Michael Paine

Water on Mars: The View From Geochemical Analyses of Martian Meteorites

>From Gullies to Glaciers: A Continuum of Evidence Supporting a Recent
Climate    Change on Mars

Impact Observations and Processes

Large Deep-Ocean Impacts, Sea-Floor Hiatuses, and Apparent Short Term
Sea-Level Changes

Shock vaporization of carbonate and sulfate minerals

Remote Sensing in the Vicinity of the El'gygytgyn Impact Crater, Siberia

Internal structure of the Chicxulub Impact crater imaged with
magnetotelluric exploration

Geophysical Signature of the Lake Bosumtwi Impact Crater, Ghana

The 2001 and 2002 Leonid Meteor Storms

First results from the 2001 Leonid storms: advances in models of meteors
and meteoroid streams

Dust in the Earth's Mesosphere: Terra Incognita

A New Atmospheric Interaction Model for Leonids Entry

NEAR and Beyond (session title)

Deep Space One's Encounter with Comet Borrelly (session title)

Advances in Modeling Flow Processes:Volcanoes, Floods, Impacts, and
Mass         Movements (session)

Ewing Structure: A Possible Abyssal Impact Crater (about the age of the
late/middle Miocene boundary, a prominent mass extinction event)

Asteroids, Meteorites, and Comets (session)

Multiplicity in the Kuiper Belt: The First Discovery of a Binary
Trans-Neptunian Object

Three Dimensional Simulation of Wave Propagation Into the Comet
46P/Wirtanen Nucleus (ROSETTA Space Mission - CONSERT Experiment)

Temporal Change of the Fireball Energy along the Fall Path from Shock
Wave Analysis

Small Comet Abundance and Solar System Location

Origin of Scour in Rampart Crater on Mars


>From Andrew Yee <>

William Steigerwald
NASA Goddard Space Flight Center, Greenbelt, MD        Dec. 7, 2001
Phone: 301/286-5017

RELEASE NO: 01-121


At the edge of our solar system lies a frigid double planet that has never
been visited by spacecraft -- Pluto. NASA's Goddard Space Flight Center,
Greenbelt, Md., has joined a team led by the Southwest Research Institute
(SwRI), San Antonio, Texas, to begin preliminary design
studies for what could be the first spacecraft to visit this remote world --
the New Horizons mission.

Goddard will provide an infrared spectrometer, called the Linear Etalon
Imaging Spectral Array (LEISA), to the camera system on board the New
Horizons spacecraft. A spectrometer breaks light down into its component
colors, much like a prism separates white light into a rainbow. Each
compound emits a unique pattern of colors, like an optical barcode. By
separating light from a celestial object into various distinct colors, a
spectrometer reveals the optical barcode of any material present. With this
information from LEISA, astronomers will determine what Pluto and Charon,
Pluto's unusually large moon, are made of, at least on their surfaces.

"We are thrilled to collaborate with the Goddard Space Flight Center," said
Dr. Alan Stern of SwRI, Principal Investigator for the New Horizons mission.
"Goddard has world-class people and world-class technology."

"Pluto is nearly three billion miles from the Sun, more than thirty times
farther away than Earth, so remote, very little is known about it," said Dr.
Donald Jennings, a Co-Investigator for New Horizons at Goddard. "Even with
the Hubble Space Telescope, Pluto's surface features remain a tantalizing
blur. Sending a spacecraft for a close-up view is the only way to learn more
about Pluto, whose moon, Charon, is so large that Pluto qualifies as a
double planet."

Congress provided $30 million in fiscal 2002 to initiate the spacecraft and
science instrument development and launch vehicle procurement for a
Pluto-Kuiper Belt mission; however, no funding for subsequent years is
included in the administration's budget plan.

If the design passes a NASA review and the mission is fully funded by
Congress, New Horizons will be sent to explore Pluto, whose orbit takes it
farther from the Sun than any planet in the solar system. Pluto is the
largest member of the Kuiper Belt. Kuiper Belt Objects (KBOs) are a class of
relatively small worlds at the fringe of our solar system, possibly hundreds
of millions strong, composed of material believed to have been left over
after the formation of the other planets.

The New Horizons mission, planned for launch in January 2006, will explore a
number of KBOs after it flies past Pluto between 2016 and 2018. The
mission's exact arrival time at Pluto depends on the rocket selected to
launch the spacecraft. On the way to Pluto, the New Horizons spacecraft will
pass close to Jupiter, gaining a boost from the giant planet's gravity to
achieve the speed necessary to reach the outer solar system in a reasonable
amount of time. This flight path will present the next opportunity to
explore Jupiter's exotic moons, and the mission intends to take full
advantage of it.

"Pluto's extreme distance makes it the only planet unexplored by
spacecraft," said Dr. Dennis Reuter, sensor program manager for LEISA. "It's
an extraordinary challenge to reach. To travel to Pluto in a practical
amount of time and survive the trip, the spacecraft and its instruments must
be built with unprecedented reliability, low weight, and low power

The camera team will provide a camera and instrument package called the
Pluto Express Remote Sensing Investigation (PERSI) that weighs less than 22
pounds and consumes less than seven watts of power. The package is comprised
of three subsystems. First is a system of six cameras, to be provided by
Ball Aerospace, Boulder, Colo., called the Multi-spectral Visible Imaging
Camera (MVIC). MVIC will take detailed pictures of Pluto and Charon. It is
called a multi-spectral
camera because it is capable of making images with various kinds of light:
visible light, ultraviolet light, and infrared light. Ultraviolet and
infrared light are not visible to the human eye.

Second is LEISA, the infrared spectrometer to be provided by Goddard. The
third subsystem is an ultraviolet spectrometer, to be provided by SwRI,
called Alice because it's such a nice name. Alice will analyze ultraviolet
light to reveal the composition of Pluto's extremely tenuous atmosphere.
Ball will be responsible for assembling the three PERSI subsystems into a
complete package.

"Each instrument team is among the best in its field, so we combined our
strengths for the New Horizons camera system, providing a package smaller
and less costly than previously possible, which is ideally suited to the
Pluto and Kuiper-belt science," said Jennings. "Goddard has supplied
infrared spectrometers for many missions, including Voyager, COBE, Cassini
and EO-1. SwRI has a strong background in space-borne ultraviolet
experiments, and is supplying Alice for the Rosetta mission. Ball has a long
and highly successful record of building a variety of space instruments."

The instrument package was developed, lab and flight tested over a period of
eight years, beginning with NASA "Advanced Technology Insertion" funds
specifically targeted at the advanced sensor and miniaturization needs of a
Pluto mission.

In addition to SwRI, Ball, and Goddard, the New Horizons team includes The
Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.,
NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., and a variety of
other universities and research institutions. APL will manage the mission
for NASA and design, build and operate the New Horizons spacecraft. JPL will
provide navigation support, and tracking and communication services through
NASA's Deep Space Network. SwRI will lead the science team and guide
development of the spacecraft's scientific instruments, while Ball Aerospace
and NASA Goddard help develop the payload.


>From Andrew Yee <>

John Bluck
NASA Ames Research Center, Moffett Field, Calif.        Dec. 7, 2001
650/604-5026 or 604-9000

AGU Moscone Center press room, rm. 111, San Francisco, Calif.
(Phone: 415/905-1007, general AGU information during meetings)



Signals that come from deep within the Earth eventually may give us a few
days' warning before some large earthquakes, according to a scientist at
NASA's Ames Research Center.

The source of these signals lies deep in the Earth's crust, where forces
squeeze rocks to the limit before they rupture catastrophically, shaking the
ground with destructive force, according to Friedemann Freund, a scientist
at NASA Ames, in California's Silicon Valley. He will present his
discoveries and theory on Wednesday, Dec. 12, at 1:30 p.m. PST in the
seismology section of Hall D, Moscone Center, San Francisco, during the 2001
American Geophysical Union (AGU) fall meeting.

"The challenge is to learn how to read and to decipher the signals," Freund
said. "The best way is to try to better understand the physics of the
processes that underlie these signals. A step forward was the discovery of
dormant electric charges in rocks in the Earth's crust," he said.

Earthquakes occur when tectonic plates, huge jigsaw-like sections of the
Earth's outermost layers, rub against each other. Sometimes they collide
head-on. In California, huge slabs of rock slide past each other, causing
temblors along the San Andreas and other fault systems.

Freund has been investigating how rocks respond to stress. "If the stress
level is high, electronic charges appear that momentarily turn the
insulating rock into a semiconductor," he said. Semiconductors are materials
that have a level of electrical conductivity between that of a metal and an
insulator, and they are used to make transistors.

"These charges are not easy to pin down. They move with impressive speed, as
fast as 300 meters (1,000 ft.) per second," he said. By measuring the
semiconductor properties of the rocks, Freund was able to show that the
charges are positive. "Normally, these charges are dormant," he said. "But
when rocks are squeezed, the charges wake up and flow out of the rock volume
in which they were generated."

When charges flow, they constitute an electric current. When there is an
electric current, there also is a magnetic field. If current varies with
time, electromagnetic waves will be emitted.

"The frequency of these electromagnetic waves will probably be very low,
much lower than radio waves, but basically of the same nature," said Freund.
"Scientists can pick them at the Earth's surface with suitable antennae or
by measuring the magnetic-field pulses that go with them."

"What happens when the charges reach the Earth's surface? They will change
'the ground,'" said Freund. "They should cause the Earth's surface to become
positively charged over a region that may measure tens or even hundreds of
kilometers. The Earth's ionosphere is bound to react," he said.

The ionosphere lies above the atmosphere, starting at about 90 km (56 mi.)
and extending to about 300 km (190 mi.) into space. "When the surface of the
Earth becomes positively charged, the charged plasma in the ionosphere must
respond," said Dimitar Ouzounov, a scientist from NASA Goddard Space Flight
Center, Greenbelt, Md., who is working with Freund. The ionospheric plasma
is very thin air that contains many free electrons and positive ions. In the
lowest layers of the
ionosphere, which reflect radio waves, the plasma is positively charged.

When the Earth's surface becomes positively charged, the plasma is pushed
aside, and energetic electrons from the upper layers can penetrate more
deeply into the lower part of the ionosphere. This in turn affects the
transmission of radio waves, especially in the short wave region, as was
noticed in the 1960s, in the days before the huge 1961 Chilean earthquake
and the nearly equally large Good Friday earthquake in Alaska in 1964.

"These ionospheric changes can also be studied from satellites. Russia,
France and Japan are close to launching satellites dedicated to
investigating these phenomena," Freund said.

"But what has been lacking in the past was a physical explanation of how
electric charges can be created in the Earth's crust," said Freund. "These
are charges that move around, emit all kinds of signals, and can even reach
the Earth's surface. There they give rise locally to very high electric
fields, and change 'the ground' charge."

"When the rocks in the Earth's crust crackle and buckle under the onslaught
of tectonic forces, the charges that are dormant in them are set free. They
give rise to a dazzling array of phenomena, long known to mankind and even
part of folklore in earthquake-prone regions around the globe," said Freund.
"These phenomena range from anomalous electric and magnetic signals, to
'earthquake lights' that illuminate the mountain tops and strange animal
behavior as well as ionospheric effects that impact how radio waves travel
over long distances."

"It is both surprising and comforting that many seemingly disjointed or even
inexplicable phenomena that point to impending earthquake activity seem to
have just one cause -- the awaking and spreading of normally dormant charges
in the rocks deep in the Earth," he said.

"It is much too early and, in fact, unwise to expect that earthquakes would
soon become predictable beyond the statistical probability that is currently
the state-of-the-art," Freund said. "But one day, we'll learn to read the
signals that the restless Earth emits before the rocks rupture with deadly


>From the BBC Online News, 10 December 2001
American and Russian crews on the International Space Station and the
shuttle Endeavour have held a televised ceremony to commemorate those who
died in the 11 September attacks in the US.
The commander of the outgoing space station crew said they had seen the
smoke over New York and Washington on the day of the attacks as they orbited
the earth.

Endeavour is carrying thousands of small flags intended for relatives of
those who died in the attacks and also has on board a flag retrieved from
the World Trade Center.

The Russian commander of the new crew said he was glad to see the US and
Russia co-operating in the anti-terror coalition.

Yuri Onofrienko said the space station programme symbolised the benefits of
international co-operation.

'Terrible' sight

Frank Culbertson, commander of the outgoing space station crew which has
been on board since August, recalled what it was like when they first heard
of the attacks.

The crew were able to see the effect of the attacks from space
"We were flying over North America at the time," he said, "so we were able
to look out one of the windows and actually see New York City under attack."

"That was quite a disturbing sight, as you can imagine... I believe all
three of us were thinking how terrible this must be for the people that were
at the point of attack and for their families," he added.

Endeavour Commander Dom Gorie also paid tribute to "the armed forces around
the world, who are doing their best to stop this global threat of

Flying high

Mr Gorie said that the shuttle was carrying 6,000 flags which will be
distributed later to the families of those killed on board the hijacked

Two were flown into the World Trade Center, one into the Pentagon and one
crashed in Pennsylvania after a passenger revolt.

Also on board is a US flag that had been flying on top of the World Trade
Center, which was later retrieved from the rubble of the collapsed

The ISS is held up as an example of international co-operation
"It has a few tears in it; you can still smell the ashes," Mr Gorie said.

"It's just a tremendous symbol of our country. Just like our country was a
little bit bruised and battered and torn, with a little repair, it's going
to fly high and as beautiful as it ever could, and that's just what our
country is doing," he added.

The shuttle is also carrying a flag found in the Pentagon after the attack,
a flag from the state of Pennsylvania and another from the New York Fire
Department, as well as a selection of shields from the New York Police

New York's emergency services were amongst those who bore the brunt of the
September attacks.

Endeavour is scheduled to return to Earth with the outgoing crew on 16

Copyright 2001, BBC



>From Michael Paine <>

Dear Benny

One of the AGU abstracts ( I mentioned
in my earlier email was on the Ewing Structure. Dallas Abbott estimates it
has a crater diameter between 55 and 150km - a significant impact - and
"about the age of the late/middle  Miocene boundary, a prominent mass
extinction event". With my limited resources I cannot find a reference to
such an extinction event but did find this interesting New Zealand site

"The middle part of the Miocene Epoch, a time period from 11 to 16
million years ago, was crucial in the development of the modern global
climate regime. It was during this period that a huge ice-sheet first
formed on eastern Antarctica, essentially shaping the earth's climate as
we see it today."

I can speculate that a major ocean impact would have released vast
quantities of seawater into the atmosphere and caused severe global colling
for at least a year. Such a combination MIGHT have been enough to start off
the ice sheet.

An interesting one to watch!
Michael Paine


>From Göran Johansson <>

Psalm 18 in the Bible has been discussed on several occasions on CCNet. And
2 Samuel 22 has also been mentioned. According to the modern comments, they
are believed to be related to each other. And the second item should be very
late during the reign of King David, unless it is anachronistic.
"When David looked up and saw the angel of the Lord standing between
earth and heaven, and in his hand a drawn sword stretched out over
Jerusalem, he and the elders, clothed in sackcloth, fell prostrate to
the ground." 1 Chronicles 21:16. 

Chronologically it may be from the same time as 2 Samuel 22. This item has
often been interpreted as a comet. Some of you are probably familiar with
the comet catalogue Ho compiled (1962, Vistas in Astronomy, vol. 5, pages
127-225) "In spring, in the 19th year of (Chou) Chao-Wang a (po) comet
appeared within the Thai-Wei (Enclosure)."
When did the comet appear? There are chronological problems but hardly
anybody would protest against a date sometime during the 970s or 960s BCE.
The story in the Bible occurred during spring but I can't tell the exact
week because I don't know when people would thresh wheat.
"The Legends of the Jews" is 7 volumes of non-Biblical Jewish legends,
edited by L. Ginzberg, which has been reprinted several times. On page 15 in
volume 5, it is mentioned that a meteorite fell down outside Jerusalem on
that place where the temple was later built. Admittedly it is improbable
that a meteorite would fall down on a specific place, so perhaps the people
moved a meteorite to the place where they later built the temple.
G H I Johansson


>From Bruce Lerro <>

Hi Benny:

Just wanted to alert you and other folks about a book called "Natural
Knowledge in Preclassical Antiquity" by Mott Greene (Johns Hopkins Press,
1992). The author has two very interesting chapters comparing the Theogony
of Hesiod to the Thera eruption and another eruption in Sicily around the
7th century BCE. The good news is Greene seems well versed in geology and
his comparison of Hesiod's  text to our current geological knowledge seems
more specific than the usual comparisons.

Bruce Lerro


>From John Twigg <j.twigg@UCL.AC.UK>

Some of you may be interested in a new working paper published online by the
Benfield Greig Hazard Research Centre.

Author: Annelies Heijmans
Title: 'Vulnerability': a matter of perception.

The paper looks at different ways of viewing vulnerability, focusing on how
poor people think of it.

You can download it from the Benfield Greig Hazard Research Centre website
( - go to the Disaster Management pages for this and
the others in the series of working papers.


>From Ananova, 8 December 2001

Scientist wants to ban Christmas trees

A Dutch scientist wants to ban all Christmas trees from houses and churches.

Freed Paap says Christmas trees are a fire safety hazard and should never be
put up indoors. He is a research scientist and safety expert.

He says its impossible to make a non-flammable Christmas tree so they should
all be banned from buildings.

Mr Paap, who works for the Netherlands Organisation for Applied Scientific
Research (TNO) said all Christmas trees in bars and restaurant, schools,
churches and public buildings should be forbidden for safety reasons.

He said materials in buildings should always be made non-flammable.

But Mr Paap says no Christmas trees, real or artificial, are non-flammable
so they should be banned from in-doors.

"It's impossible to make them really not inflammable," Mr Paap said.

"The results for artificial trees are much better but not really sufficient.
Therefore all christmas trees should be forbidden," he told Utrechts

Holland suffered a horrific Christmas tree related inferno accident last

On New Years Day 2001, 14 teenagers were killed and 184 injured in a fire in
a pub in Volemdam which was caused by burning Christmas tree twigs.

Copyright 2001, Ananova

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