PLEASE NOTE:
*
CCNet 77/2001 - 8 June 2001
---------------------------
"Composite images of Saturn's rings, taken by NASA's Hubble
Space
Telescope, have revealed mysterious color variations that hint
that
the rings could be made of materials from the outer solar system.
[...]
This leads scientists to suspect that, unlike the moons, the
rings were
formed from an outer solar system object. This object, they
think, careened
too close to Saturn and -- like comet Shoemaker-Levy 9 in
1994 -- was
torn apart by the massive planet's gravity, leaving a trail of
debris."
--Kathleen Burton, NASA Ames Research Center, 7 June 2001
"The SDSS observations also showed that the two types of
asteroids
are spatially separated with the inner belt of rocky asteroids
centered at
about 2.8 AU from the sun and the outer belt of carbonaceous
asteroids
centered at about 3.2 AU. This distribution has important
implications for unraveling how the solar system formed and
suggests that
planet migrations that seem to be common in other planetary
systems have
not occurred in ours."
--Tom Quinn, University of Washington, 5 June 2001
(1) SATURN'S 'TILTED' RINGS REVEAL MYSTERIOUS COLOR VARIATIONS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(2) EARLY RESULTS FROM THE SLOAN DIGITAL SKY SURVEY
Ron Baalke <baalke@jpl.nasa.gov>
(3) SUBARU TEAM DISCOVER SMALL OBJECTS IN OUTER SOLAR SYSTEM
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) NASA SELECTS TWO INVESTIGATIONS FOR PLUTO-KUIPER BELT MISSION
FEASIBILITY STUDIES
NASANews@hq.nasa.gov
(5) MARS EXPRESS TO INVESTIGATE PHOBOS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(6) INTERSTELLAR SPACE A LIKELY SOURCE OF ORGANIC MOLECULES
Andrew Yee <ayee@nova.astro.utoronto.ca>
(7) YET MORE ON GIORDANO BRUNO
Paul Withers <withers@lpl.arizona.edu>
(8) 100KM CIRCULAR FEATURE OFF THE COAST OF VIETNAM
Michael Paine <mpaine@tpgi.com.au>
(9) AN OPEN INVITATION
Leon Neihouse <neihouse@gwi.net>
(10) SNIPPETS FROM EDINBURGH EARTH SYSTEM PROCESSES CONFERENCE
Michael Paine <mpaine@tpgi.com.au>
(11) AND FINALLY: RESEARCHERS BLAME HUNGRY HOMO SAPIENS FOR LATE
QUATERNARY
MASS EXTINCTION
BBC News Online, 7 June 2001
============
(1) SATURN'S 'TILTED' RINGS REVEAL MYSTERIOUS COLOR VARIATIONS
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Kathleen Burton
NASA Ames Research Center, Moffett Field,
CA June 7, 2001
(Phone: 650/604-1731 or 604-9000)
E-mail: kburton@mail.arc.nasa.gov
RELEASE: 01-36AR
SATURN'S 'TILTED' RINGS REVEAL MYSTERIOUS COLOR VARIATIONS
Composite images of Saturn's rings, taken by NASA's Hubble Space
Telescope,
have revealed mysterious color variations that hint that the
rings could be
made of materials from the outer solar system. These new findings
are
important because scientists have long questioned whether the
rings
originated around Saturn, like the planet's retinue of icy moons,
or
elsewhere.
The Hubble images, captured by a team of scientists between 1996
and 2000,
show Saturn's rings from beneath in a wide-open or
"tilted" viewpoint from
Earth, as the planet's Northern Hemisphere swings from autumn
toward winter.
When seen edge-on, Saturn's rings, which are only some tens of
meters thick,
nearly disappear from view. The composite images, which were
released today
by the Hubble Heritage program, can be accessed at:
http://heritage.stsci.edu
"The color of the ring material can help tell us what the
rings are made of
and will help decipher their origin," said Dr. Jeff Cuzzi,
of NASA's Ames
Research Center and a member of the Hubble team. The color
variations
indicate that different materials make up the rings. The
distribution of the
materials provides information about the processes that shaped
the rings, he
explained.
"Most people don't know that Saturn's rings aren't white but
have a faint
salmon color, which hints that a few percent of complex organic
molecules
are mixed in with the water ice the rings are mostly made
of," Cuzzi said.
Saturn's seven small icy moons don't have such a reddish color,
but many icy
objects in the frozen reaches of the outer solar system do, he
explained.
This leads scientists to suspect that, unlike the moons, the
rings were
formed from an outer solar system object. This object, they
think, careened
too close to Saturn and -- like comet Shoemaker-Levy 9 in
1994 -- was torn
apart by the massive planet's gravity, leaving a trail of debris.
Over 100 Hubble images were analyzed in eight different colors
that cover,
and go beyond, the range of human vision. They include violet,
blue, green
and red in the visible range and ultraviolet and infrared in the
non-visible
range.
Cuzzi also has shown that there appear to be at least two unknown
materials
mixed with the rings' water ice, and that the way these materials
are
distributed in the rings is unlike anything seen on the surfaces
of nearby
planets or satellites. For example, in some rings
the color gets redder closer to Saturn, and in others, the color
trend
reverses in the middle of the ring. In some places, the color
gets redder
where the concentration of particles increases, and in other
places it gets
redder where the concentration of particles decreases. Scientists
hope to
explain these variations in terms of how the composition of the
ring
material was initially distributed, and how it has evolved with
time.
The Hubble data also show that the ring color changes with
viewing angle.
The best explanation, said Dr. Francois Poulet of NASA Ames, who
is working
with Cuzzi, is that the ring particles are actually lumpy
aggregates of
particles, with many more deep shadows than the relatively smooth
surface of
a moon or asteroid. The lit parts of the "lumpy"
surface partly illuminate
the shadows with their reddish color, so the rings appear redder
as more
shadows are seen.
Cuzzi believes that observations like these, while not currently
understood,
eventually will provide insights into the processes by which
Saturn's ring
structure was formed and continues to evolve. He noted that the
Cassini
spacecraft, which recently passed Jupiter en route to a four-year
tour of
the Saturn system starting in July 2004, carries several
instruments that
will provide much finer detail and greatly improve the ability to
identify
these non-icy constituents in the rings and the structure of the
particles.
The Cassini mission also includes an atmospheric entry probe into
the
organic smog-shrouded moon Titan, which might have lakes or seas
of liquid
ethane on its frigid surface.
Cuzzi's collaborators include Drs. R. French of Wellesley
College, L. Dones
of Southwest Research Institute, Mark Showalter of Stanford
University, and
Paul Estrada of Cornell University.
The Space Telescope Science Institute (STScI) is concurrently
issuing a news
release on the data, "A Change of Seasons On Saturn."
It can be accessed,
together with electronic images, animation and additional
information, at:
http://oposite.stsci.edu/pubinfo/pr/2001/15
NASA's Hubble Space Telescope is a project of international
cooperation
between NASA and the European Space Agency.
===========
(2) EARLY RESULTS FROM THE SLOAN DIGITAL SKY SURVEY
From Ron Baalke <baalke@jpl.nasa.gov>
http://www.sdss.org/news/releases/20010605.edr.html
Sloan Digital Sky Survey
Media Contacts
Michael
Turner
Steve Koppes
SDSS Scientific
Spokesman
University of Chicago
773-702-7974
773-702-8366
mturner@oddjob.uchicago.edu
s-koppes@uchicago.edu
Georgia
Whidden
Satoru Ikeuchi
Institute for Advanced
Study Japan
Participation Group
609-734-8239
81-52-789-2427
gwhidden@ias.edu
ikeuchi@a.phys.nagoya-u.ac.jp
Michael
Purdy
Hans-Walter Rix
The Johns Hopkins
University
Max-Planck-Institut für Astronomie
410-516-7906
49-6221-528-210
mcp@jhu.edu
rix@mpia-hd.mpg.de
Rene
Walterbos
Barbara Kennedy
Nex Mexico State
University
Pennsylvania State University
505-646-5990
bkk1@psu.edu
rwalterb@nmsu.edu
Steve
Schultz
Vince Stricherz
Princeton
University
University of Washington
609-258-5729
206-543-2580
sschultz@princeton.edu
vinces@u.washington.edu
Steven
Dick
Bruce Gillespie
U.S. Naval
Observatory
Apache Point Observatory
202-762-0379
505-437-6822
dick.steve@usno.navy.mil
gillespi@apo.nmsu.edu
Amber
Jones
Ray Villard
National Science
Foundation Space
Telescope Science Institute
703-292-8070
410-338-4514
ajones@nsf.gov
villard@stsci.edu
For release after 9:15 a.m. PDT, June 5, 2001
SDSS 01-01
Early results from the Sloan Digital Sky Survey: From under our
nose to the
edge of the universe
Pasadena, Calif. -- Scientists of the Sloan Digital Sky Survey
today (June
5) presented results based on early data from the project. The
first
glimpses of what will ultimately be the most comprehensive and
fully digital
map of the sky included identification of the two most distant
objects ever
observed; new light on asteroids; and the first SDSS results on
the
large-scale distribution of galaxies.
Sky Survey collaborators also announced the release to the
worldwide
astronomy community of the first large piece of the digital sky.
[snip]
Asteroids
The SDSS collaborators presented the first clear evidence for
chemical
segregation in the belt of asteroids between Mars and Jupiter.
By viewing the asteroids in five color bands, explained Dr. Tom
Quinn of the
University of Washington, the SDSS survey can reliably separate
individual
asteroids into two main classes, rocky silicate asteroids and
more primitive
carbonaceous asteroids.
"The SDSS observations also showed that the two types of
asteroids are
spatially separated," Quinn said, "with the inner belt
of rocky asteroids
centered at about 2.8 AU from the sun and the outer belt of
carbonaceous
asteroids centered at about 3.2 AU. This distribution has
important
implications for unraveling how the solar system formed and
suggests that
planet migrations that seem to be common in other planetary
systems have not
occurred in ours."
One astronomical unit, or AU, corresponds to the distance from
the sun to
the earth.
The SDSS asteroid sample also turned up another surprise.
"There appear to be fewer asteroids smaller than about 4 km
in diameter in
the asteroid belt than we previously thought," said Dr.
Zeljko Ivezic of
Princeton University, the leader of the SDSS asteroid team.
"Since the
asteroid belt is believed to be the reservoir for Earth-crossing
asteroids,
the new SDSS observations suggest that future asteroid collisions
with Earth
may be less likely than previously believed."
The SDSS scanning technique allows only five minutes to follow
celestial
objects as they move across the field of view, said Dr. Robert
Lupton of
Princeton University. During this time asteroids appear to move a
distance
just 1/1000th the size of the moon, relative to the distant
stars.
"Nevertheless," Lupton said, "we can reliably
detect their tiny motions and
even determine their orbital motions around the sun."
The asteroid observations rely on precision position-finding
software
developed by SDSS collaborators at the US Naval Observatory.
Images available:
[snip]
Asteroids:
* Diagram of asteroid belt
http://www.sdss.org/news/releases/20010605.edr.img7.html
* Graph of asteroid belt cross section
http://www.sdss.org/news/releases/20010605.edr.img7.html
* Asteroid size distribution
http://www.sdss.org/news/releases/20010605.edr.img9.html
============
(3) SUBARU TEAM DISCOVER SMALL OBJECTS IN OUTER SOLAR SYSTEM
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Subaru Telescope
National Astronomical Observatory of Japan
Hilo, Hawaii
May 23, 2001
Subaru Discovers Small Objects in Outer Solar System
A Solar System research team from the National Astronomical
Observatory of
Japan (NAOJ), the Graduate University for Advanced Studies, and
the Science
University of Tokyo have discovered small objects extended within
the outer
solar system using Subaru Telescope. Although more than 350 such
objects are
now known, these are the first discovered by Japanese
astronomers.
Around 1950, Edgeworth and Kuiper independently proposed that
there should
be many small objects in the outer solar system that never became
planets.
We call them "Edgeworth-Kuiper Belt Objects (EKBOs)."
Since we believe that
they are composed of the materials of the early Solar System in
their
original state, EKBOs should be very useful objects for teaching
us about
how the Solar System formed. EKBOs may also be the source of the
short-period comets, according to computer simulations.
The first EKBO was discovered with the University of Hawaii's
24" telescope
at the summit of Mauna Kea in August 1992. In the nine years
since the
discovery of this EKBO (named 1992 QB1), more than 350 EKBOs have
now been
observed.
On UT February 21 and 24, 2001, the Japanese team of astronomers
[ http://subarutelescope.org/Latestnews/200105/EKBO/observing.jpg
, 69KB]
discovered nine candidates for new EKBOs using the Subaru
prime-focus camera
(Suprime-Cam). Since two of the nine objects have observations on
both days
and their initial orbits have been determined, the International
Astronomical Union has classified them as EKBOs and given them
provisional
designations "2001 DR106" and "2001 DS106."
The distance between the objects
and the earth is approximately 6.3 billion kilometers and their
brightness
is approximately 25th magnitude, a value about forty million
times fainter
than what can be seen with the unaided human eye (sixth
magnitude). The
objects are estimated to be approximately 100 kilometers in
diameter,
about 10% the size of the largest asteroid Ceres (910
kilometers). These
observations show that the projected surface density of objects
the size of
these two EKBOs is approximately 10 per square degree along the
plane of the
ecliptic, consistent with previous results.
Compared to the asteroids which exist between the orbits of Mars
and
Jupiter, the motion of EKBOs against the stellar background is
very slow
because they are much further from the Sun. Mr. Daisuke Kinoshita
(Grad.
Univ. for Advanced Studies) and Mr. Naotaka Yamamoto (Science
Univ. of
Tokyo) have developed an auto-detection program for slow moving
EKBOs. They
comment, "I tremendously realized the great performance of
Subaru and
Suprime-Cam"; "it's impossible to describe the
impression when I look at the
results of the program." According to Dr. Jun-ichi Watanabe
(NAOJ), the team
leader, "Subaru's wide-field and big mirror offers the
highest performance
in the world for this type of work, and I fully expect more
discoveries to
be made." This is just the starting point for Subaru's EKBO
studies.
The results are reported in Minor Planets Electric Circular MPEC
2001-J33
(http://cfa-www.harvard.edu/mpec/K01/K01J33.html)
issued on May 15, 2001.
IMAGE CAPTION:
[ http://subarutelescope.org/Latestnews/200105/EKBO/2001DR106.gif
, 56KB ]
The images of 2001 DR106: the left is at 07:35:36UT on 2001/02/24
and the
right is 08:31:03UT on the same date.
==========
(4) NASA SELECTS TWO INVESTIGATIONS FOR PLUTO-KUIPER BELT MISSION
FEASIBILITY STUDIES
From NASANews@hq.nasa.gov
Donald Savage
Headquarters, Washington,
DC
June 6, 2001
(Phone: 202/358-1547)
RELEASE: 01-114
NASA SELECTS TWO INVESTIGATIONS FOR
PLUTO-KUIPER BELT MISSION FEASIBILITY STUDIES
In the first step of a potential
two-step process, NASA has selected
two proposals for detailed mission feasibility studies as
candidates for a
Pluto-Kuiper Belt (PKB) mission to explore the only planet in our
Solar
System yet to be visited by a spacecraft from Earth.
The President's FY 2002 budget request does not contain
development funding
for a Pluto mission. The Congress requested that NASA not
do anything
precipitous which would preclude the ability to develop a
Pluto-Kuiper
mission until the Congress could consider it in the context of
the FY 2002
budget. If funding is provided in the FY 2002 budget and either
proposal is
ultimately selected, the Agency could down-select a proposal for
development
to ultimately fly a spacecraft to Pluto and beyond. If a PKB
mission is
developed, launch would be in the 2004-2006 time frame and the
spacecraft
would arrive at Pluto before 2020.
"The PKB mission represents a possible opportunity to visit
the only planet
not yet explored by spacecraft," said Dr. Colleen Hartman,
Pluto Program
Director in NASA's Office of Space Science, Washington, DC.
"It's really an
opportunity to, in a sense, look into a deep-freeze of history
which could
tell us how our Solar System evolved to what it is today,
including the
precursor ingredients of life."
Each team will receive $450,000 to conduct a three-month concept
study. At
the end of the three months, NASA will thoroughly evaluate
program content
and technical, schedule and cost
feasibilities of both proposals to determine if either is
selectable.
The two selected proposals were judged to have the best science
value among
the five proposals submitted to NASA in April 2001 in response to
the
Pluto-Kuiper Belt Mission Announcement of Opportunity. Each
selected
investigation will work with the Office of Space Science at NASA
Headquarters to finalize the design of the spacecraft and its
accommodation
of the instrument sets.
The selected investigations are:
Pluto and Outer Solar System Explorer (POSSE). Dr. Larry
Esposito, Principal
Investigator, University of Colorado, Boulder, will lead a team
including
the following major participants: NASA's Jet Propulsion
Laboratory (JPL),
Pasadena, CA; Lockheed Martin Astronautics, Denver; Malin Space
Science
Systems, Inc., San Diego; Ball Aerospace Corp., Boulder, CO; and
University
of California, Berkeley.
New Horizons: Shedding Light on Frontier Worlds. Dr. S. Alan
Stern,
Principal Investigator, Southwest Research Institute, Boulder,
CO, will lead
a team including the following major participants: Johns Hopkins
University
Applied Physics Laboratory, Laurel, MD; Ball
Aerospace Corp.; Stanford University, Palo Alto, CA; NASA's
Goddard Space
Flight Center, Greenbelt, MD; and JPL.
Both proposals are for complete missions, including launch
vehicle,
spacecraft and science instrument payload. Both address the major
science
objectives defined in the original announcement. Each proposal
includes a
remote sensing package that includes imaging
instruments, a radio science investigation, and other experiments
to
characterize the global geology and morphology of Pluto and
Charon, map
their surface composition, and characterize Pluto's neutral
atmosphere and
its escape rate.
Pluto is a different kind of planet. It is not a rocky planet
like Earth,
Mars, Mercury or Venus, or a gas giant like Jupiter, Saturn,
Uranus or
Neptune. It is a Kuiper Belt Object, a class of objects composed
of material
left over after the formation of the other planets, which has
never been
exposed to the higher temperatures and solar radiation levels of
the inner
solar system.
It is known that Pluto has large quantities of ices of nitrogen,
and simple
molecules containing combinations of carbon, hydrogen and oxygen
that are
the necessary precursors of life. These ices would be largely
lost to space
if Pluto had come close to the Sun. Instead they remain on Pluto
as a
representative sample of the primordial material that set the
stage for the
evolution of the Solar System as it exists today, including life.
If a PKB mission is developed, it will be a Principal
Investigator-led
investigation, bringing together teams from academia, industry,
NASA Centers
and other communities, and will be developed following the highly
successful
management philosophy of the Discovery Program.
=============
(5) MARS EXPRESS TO INVESTIGATE PHOBOS
From Andrew Yee <ayee@nova.astro.utoronto.ca>
ESA Science News
http://sci.esa.int
07 Jun 2001
Mars Express to investigate Phobos
Phobos, the tiny innermost moon of Mars, is to come under
unprecedented
scrutiny after Europe's mission to Mars goes into orbit around
the Red
Planet late in 2003. Mars Express is due to pass within 3000 km
of the
22 km diameter moon a few hundred times during its two-year
nominal
mission lifetime.
"There will be many more opportunities for close fly-bys
than during NASA's
Viking mission," says Tom Duxbury from NASA's Jet Propulsion
Laboratory, a
veteran of previous Phobos observations who is helping to plan
the Mars
Express observation campaign.
At a distance of 3000 km, the High Resolution Stereo Camera
(HRSC) on board
Mars Express will be capable of taking images with a resolution
at least as
good as any taken by Viking. At 1000 km, the Infrared and Visible
Mapping
Spectrometer (OMEGA) will also be switched on to map the mineral
composition
of the tiny moon's surface; and when the distance is only a few
hundred
kilometres, the Planetary Fourier Spectrometer (PFS) and the
Sub-surface
Sounding Radar/Altimeter (MARSIS) will record measurements. The
Energetic
Neutral Atoms Analyser (ASPERA) will monitor the plasma
environment around
the orbit of Phobos during all fly-bys.
"Mars Express will provide the first global map of Phobos.
This is important
because we know one side of this moon well, but the other side is
less
well-known," says Agustin Chicarro, ESA's Mars Express
project scientist.
"We should get a complete view of the satellite in terms of
its topography,
sub-surface and composition. This should help us determine once
and for all
whether it is a captured asteroid or not," he adds.
Mars Express could generate the most comprehensive suite of
observations
ever recorded for Phobos. They will help to resolve some of the
outstanding
puzzles about the Martian moon, many of which came to light
during previous
observation missions. In addition to Viking, these included the
ill-fated
Russian mission, Phobos-2, and NASA's Mars Global Surveyor, which
is still
on mission around the Red Planet. Phobos-2 was due to send a
lander to the
tiny moon in 1989, but was lost just 100 km above the surface.
Phobos is a world of mysterious origin and destiny. It is light,
with a
density less than twice that of water, and orbits just 5980 km
above the
Martian surface. One idea is that Phobos and Deimos, Mars's other
moon,
are captured asteroids. Data returned by the infrared mapping
spectrometer
experiment (ISM) on board the Phobos-2 mission supported this
view.
"In general the composition matched that of the inner
asteroids. But
we don't know whether Phobos is primordial or whether it has
undergone
transformation," says Jean-Pierre Bibring, principal
investigator for ISM
and also for OMEGA on Mars Express. "We found some
tantalising evidence
for transformation in the form of interesting minerals at the
bottom of a
crater, which were absent elsewhere on Phobos, suggesting that
the bulk
composition is inhomogeneous. I'm very excited about observing
Phobos
again because OMEGA will have much higher resolution and will be
able to
determine the surface composition unambiguously and pick out
minerals at
the bottom of craters, thus determining the bulk
composition."
However, there are other ideas about the origin of these two
moons. One,
favoured by Duxbury, is that they are lightly accumulated ejecta
from
asteroid impacts on the Martian surface, with Phobos composed of
ejecta
orbiting Mars faster than the planet rotates and Deimos, whose
orbit is
further out and orbital motion slower, composed of ejecta
orbiting more
slowly than the planet rotates.
Another mystery about Phobos concerns the origin of deep grooves
on its
surface. Some of these radiate from Stickney, the large impact
crater
that distorts the shape of the moon, and are thought to indicate
that
the force of the impact nearly shattered the small body. However,
others
on the central portion of Phobos run almost parallel and have
prompted
another thought.
John Murray, from the Open University in the United Kingdom, and
a
co-investigator on the HRSC, thinks that the grooves are strings
of
impact craters made by ejecta thrown up by major impacts on Mars.
He has
calculated the velocity of such ejecta and the position and
direction of
the 'grooves' they might be expected to leave on Phobos.
"The direction
of the grooves corresponds to what the hypothesis predicts,"
he says.
"There are no grooves on the trailing edge of Phobos, which
is also what
you'd expect."
However, the leading edge of Phobos has never been imaged in
close up
before and the appearance of grooves here will be critical to the
theory.
The HRSC on Mars Express should provide the required images for
the first
time. "If I'm right, we should see wider chains of grooves
crossing at
all angles here," says Murray.
For further information please contact:
ESA Science Programme Communication Service
Tel: +31 71 5653183
USEFUL LINKS FOR THIS STORY
* Mars Express home page
http://sci.esa.int/marsexpress
* Mars Express instruments
http://sci.esa.int/structure/content/index.cfm?aid=9&cid=1995
* Phobos and Deimos -- some facts and historical anecdotes
http://spdext.estec.esa.nl/content/doc/ca/27338_.htm
IMAGE CAPTIONS:
[Image 1:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=27328&ooid=27332
]
The giant Stickney crater on Phobos is clearly visible on this
Viking image.
One of the most striking features on the 27 km diameter,
irregularly shaped
Phobos is the presence of grooves over most of its surface. The
grooves seem
to radiate in all directions from the giant Stickney crater
(left) and
converge on the opposite side of the satellite at a region close
to the
Stickney antipode. The grooves are best developed near Stickney,
where some
measure 700 m across and 90 m deep. However, most of the grooves
have widths
and depths in the 100 - 200 m and 10 - 20 m ranges, respectively.
[Image 2:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=27328&ooid=27333
]
Deimos, the companion moon of Phobos, was also imaged by the
Viking Orbiter.
This computer mosaic of Deimos was made with images acquired from
the Viking
Orbiter during one of its close approaches to the moon. The 15 km
diameter
Deimos circles Mars every 30 hours. Scientists speculate that
Deimos and its
companion moon Phobos were once passing asteroids that were
pulled in by the
gravity of Mars.
[Image 3:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=27328&ooid=27329
]
One of the highest resolution images to date of Phobos obtained
with the
Mars Orbiter Camera. This image of Phobos was taken with the Mars
Orbiter camera
on the Mars Global Surveyor (MGS) on August 19, 1998, 10 AM PDT.
The MGS
spacecraft was approximately 1080 km from Phobos at closest
approach. This
image, about 8.2 km wide by 12 km tall, shows the full
field-of-view of the
Mars Orbiter Camera (MOC) as spacecraft motion swept across the
satellite.
The image as shown here has a scale of 12 m per picture element.
Credit:
Malin Space Science Systems/NASA
[Image 4:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12&oid=27328&ooid=27132
]
ESA's Mars Express mission will also obtain valuable measurements
on Phobos,
the largest of the Martian moons.
===========
(6) INTERSTELLAR SPACE A LIKELY SOURCE OF ORGANIC MOLECULES
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Astrochemistry Laboratory
Ames Research Center
Moffett Field, CA
Contact information:
Dr. Louis J. Allamandola
NASA-Ames Research Center
650-604-6890, lallamandola@mail.arc.nasa.gov
Dr. Max P. Bernstein
Astrophysics Branch, NASA-Ames Research Center
650-604-0194, mbernstein@mail.arc.nasa.gov
Dr. David Deamer
Dept. of Chemistry and Biochemistry, UC Santa Cruz
831-459-5158, deamer@hydrogen.UCSC.EDU
Dr. Jason P. Dworkin
Astrophysics Branch, NASA-Ames Research Center
650-604-0789, jdworkin@mail.arc.nasa.gov
Ms. Jamie Elsila
Dept. of Chemistry, Stanford University
650-723-4318, jelsila@Stanford.EDU
Dr. Scott A. Sandford
Astrophysics Branch, NASA-Ames Research Center
650-604-6849, ssandford@mail.arc.nasa.gov
Dr. Richard N. Zare
Dept. of Chemistry, Stanford University
650-723-3062, zare@stanford.edu
FOR RELEASE: 10:00 AM PDT, June 4, 2001
INTERSTELLAR SPACE A LIKELY SOURCE OF ORGANIC MOLECULES
Scientists today described how the interaction of hard radiation
and ices
in space leads to the production of complex organic molecules.
The report
is being presented to the American Astronomical Society meeting
in Pasadena,
CA by Drs. Louis Allamandola, Max Bernstein, Jason Dworkin, and
Scott
Sandford of the Astrophysics Branch of NASA's Ames Research
Center, in
Moffett Field, CA, Dr. David Deamer of the Biochemistry
Department of the
University of California, in Santa Cruz, CA, and Dr. Richard Zare
and Ms.
Jamie Elsila of the Department of Chemistry at Stanford
University, in
Stanford, CA. The production of organic compounds in space is of
special
interest to scientists since these molecules may have played a
role in the
origin of life on Earth.
These scientists have been studying the chemistry of organic
carbon
compounds that occurs in dense molecular clouds in interstellar
space,
the locations where new stars and planetary systems are born.
Such clouds
consist of concentrations of dust, ice, and gas that screen out
much of
the light produced by outside stars. As a result, the interiors
of these
clouds can become very cold, sometimes attaining temperatures as
low as
10 Kelvin (-263 C). At these temperatures, many of the molecules
and atoms
that are normally present as gases condense to form ice mantles
surrounding
the dust particles in the cloud, much as your breath condenses
into frost
on a cold window. These ices are primarily made up of simple
molecules like
water (H2O), methanol (CH3OH), carbon dioxide (CO2), carbon
monoxide (CO),
ammonia (NH3), and methane (CH4).
At such low temperatures, these molecules would not normally be
expected to
react with each other, particularly when they are embedded in
ice. However,
the ice mantles are exposed to low levels of ionizing radiation
in the form
of cosmic rays and ultraviolet photons. This radiation can break
apart the
molecules in the ice and produce highly reactive ions and
radicals that
can recombine to form larger, more complex molecules.
At NASA-Ames, Allamandola, Sandford, Bernstein, and Dworkin use
cryogenically cooled vacuum chambers and UV lamps in their
laboratory to
form and irradiate interstellar ice analogs under conditions that
simulate
those found in dense interstellar clouds. "Basically, we
freeze mixed
gases onto an extremely cold window and then give the ices the
equivalent
of a good suntanning," says Allamandola. "After the
sample is warmed up,
we can remove any remaining organic materials from the sample
chamber and
study them using a variety of analytical techniques," he
continued.
One of these is the technique of two step laser-desorption
laser-ionization
mass spectrometry. "That's quite a mouthful," says
Stanford graduate
student Elsila, "but essentially this is an analytical
technique that
allows us to measure the masses of the various compounds in the
organic
residue that results from the ice irradiation." "The
surprise," says Zare,
leader of the Stanford group, "is just how complex the
population of
organics is. Generally we see a peak at virtually every mass up
to and
beyond 500 atomic mass units!" This means that the residue
must contain
hundreds of distinctly different molecules, the vast majority of
them
being considerably larger than the molecules that made up the
original ice.
"We are only just beginning to identify all the compounds
that are present,"
notes Dworkin. "One of the more interesting classes of
compound we have
identified in the residues are amphiphiles. These molecules have
the
interesting property that, if you add them to water, they can
spontaneously
form vesicles, that is, walled structures reminiscent of
cells." This
raises the possibility similar materials could have fallen on the
early
Earth and played a role in the formation of the first cellular
structures.
"There is some precedence for this idea," notes Deamer,
a biochemist from
UCSC and an expert on membranes. "Primitive meteorites are
also known to
contain amphiphiles that, when added to water, make structures
that are
very similar to those we make from the simulated interstellar
residues,"
he continued.
Other chemical compounds the team has been studying is a class of
molecules
called "polycyclic aromatic hydrocarbons," or PAHs for
short. These
molecules consist of small sheets of carbon atoms arranged in
hexagons with
hydrogen atoms around their edges, much like the shapes you would
get if
you cut out pieces of a chicken wire fence. PAHs are common
molecules on
the Earth and are a major component of auto exhaust and soot.
PAHs are also
very abundant in space, where they are thought to originate
primarily in
the outflows of gas given off by stars like our own Sun when they
reach the
end of their normal lives. Like the other molecules in space,
PAHs should
be frozen into the ice mantles that surround dust grains in
interstellar
clouds.
When the team examined the chemistry that occurred when
PAH-containing H2O
ices were irradiated with ultraviolet light, they discovered that
the PAHs
were not destroyed, but that many of them did have their edges
modified by
the addition of extra oxygen and hydrogen atoms. The addition of
oxygen
atoms results in the formation of aromatic alcohols and ketones,
i.e., PAHs
where a peripheral H atom is replaced by an -OH group or a doubly
bonded
oxygen, respectively. The aromatic ketones are of particular
interest.
This class of compounds includes quinones, molecules that
currently play
critical metabolic roles in the biochemistry of all living
organisms on
Earth. "As with the amphiphiles, this raises the interesting
possibility
that the infall of materials made in the interstellar medium may
have
played a significant role in getting life started on Earth,"
notes
Bernstein, who along with Dworkin, makes most of the residues.
"However," Allamandola added, "the production of
organics in space can't
play a role in the origin of life on planets if the material is
unable to
safely survive transportation from the interstellar medium to the
surface
of a newly formed planet. Fortunately, meteorites provide us with
evidence
that organic materials can survive this transition." This
evidence comes
primarily from the detection of deuterium enrichments in many
meteoritic
organics.
Deuterium is one of the heavier isotopes of hydrogen, having one
extra
neutron. "It turns out that most of the chemical processes
that we think
occur in the interstellar medium favor the heavier deuterium over
normal
hydrogen," says Sandford. "As a result, the presence of
excess deuterium
in meteoritic organics strongly suggests an interstellar
connection. One
of our current research activities is to try to understand how
deuterium
behaves during our ice chemistry simulations. We are discovering
patterns
to the placement of deuterium in the resulting organics and one
of our
plans for the future is to compare our results to meteoritic
organics to
see if the same patterns appear in them."
Perhaps the most important point of all this, notes Sandford, is
that this
type of chemical activity is a universal process that should be
happening
in all interstellar dense clouds. "It appears that the
universe is, in
some sense, 'hardwired' to produce relatively complex
organics," he quips.
"Furthermore, since it is from these clouds that new
planetary systems
are made, it is reasonable to expect that essentially all new
planets
should have some of this material fall on them. Thus,
interstellar
organics may play a wider role in the formation of life on other
planets,
not just the Earth."
This work was funded by the National Aeronautics and Space
Administration.
More information:
* The Astrochemistry Lab at NASA Ames
http://web99.arc.nasa.gov/~astrochm/index.html
* The equipment used to simulate space (center image)
http://web99.arc.nasa.gov/~astrochm/equipment.html#Anchor-49575
* Related material in the July 1999 issue of Scientific American
http://www.sciam.com/1999/0799issue/0799bernstein.html
Related material which has appeared in the scientific literature:
* Bernstein, M. P., Sandford, S. A., Allamandola, L. J.,
Gillette, J. S.,
Clemett, S. J., & Zare, R. N. (1999). UV Irradiation
of Polycyclic
Aromatic Hydrocarbons in Ices: Production of Alcohols,
Quinones, and
Ethers. Science 283, 1135-1138.
http://web99.arc.nasa.gov/~astrochm/Bernsteinetal1999.pdf
* Bernstein, M. P., Dworkin, J. P., Sandford, S. A., &
Allamandola, L. J.
(2001). Ultraviolet Irradiation of Naphthalene in H2O Ice:
Implications
for Meteorites and Biogenesis. Meteoritics and Planetary
Science, 36,
351-358.
http://web99.arc.nasa.gov/~astrochm/Bernsteinetal2001.pdf
* Dworkin, J. P., Deamer, D. W., Sandford, S. A., &
Allamandola, L. J.
(2001). Self-Assembling Amphiphilic Molecules: Synthesis
in Simulated
Interstellar/Precometary Ices. Proc. Nat. Acad. Sci. 98,
815-819.
http://web99.arc.nasa.gov/~astrochm/Dworkinetal2001.pdf
Images of vesicle research:
[Image 1: http://web99.arc.nasa.gov/~astrochm/drops.jpg
(286KB)]
These droplets (~10 microns across) show structures reminiscent
of cells
(although they are not alive). They are from a chemically
separated
fraction of the bulk residue.
[Image 2: http://web99.arc.nasa.gov/~astrochm/fraction.jpg
(167KB)]
These droplets (small ones are ~10 microns across) glowing under
black
light in the microscope show internal structure and suggest
chemical
complexity. They are from a chemically separated fraction of the
bulk
residue.
[Image 3: http://web99.arc.nasa.gov/~astrochm/vesicle.jpg
(85KB)]
This is a vesicle (~10 microns across) glowing under black light
in the
microscope made from the bulk residue. Proof that it is a hollow
vesicle,
rather than a simple drop of oil, is the green pyranine dye which
we have
trapped inside of it.
============================
* LETTERS TO THE MODERATOR *
============================
(7) YET MORE ON GIORDANO BRUNO
From Paul Withers <withers@lpl.arizona.edu>
Hi Benny,
Some responses to the discussions on CCnet... Please split them
up and post
them as you wish. The common theme seems to be reading the press
release
without reading the peer-reviewed paper.
Paul Withers
Re: http://abob.libs.uga.edu/bobk/ccc/cc050901.html
- 6 (Paine)
The Meteoritics paper gives a range of possible sizes for the
impactor that
formed Giordano Bruno as 1 - 3 km depending on the speed of the
impactor
(the Holsapple 1993 reference). 850m is close enough to the low
end of this
range. In any case, the estimate of how often craters of a
given size are formed is referenced by crater size, not impactor
size (the
Neukum and Ivanov 1994 reference). The 15 million year estimate
doesn't care
if we are at the small or large end of the 1-3 km size range.
Re: http://abob.libs.uga.edu/bobk/ccc/cc050201.html
- 8 (Baillie)
There are significant physical differences between hailstones and
meteorites
derived from a lunar impact. Either the ejecta from the lunar
impact would
burn up completely in the atmosphere, in which case the Scots
would have
seen nothing bouncing on the ground to misidentify as hailstones,
or some of
it reaches the ground intact, in which case the ground is covered
with lots
of meteorites which, unlike hailstones, do not quickly melt away.
Maybe the
Scots sheltered from a "hailstorm" then went out, found
a load of
meteorites, and had no better way to describe
what happened than as a hailstorm. I think that the chronicler
would have
found some way to describe the interesting fact that the ground
was covered
in new rocks after the hailstorm if the hailstorm was actually a
meteor
storm.
Re: http://abob.libs.uga.edu/bobk/ccc/cc050201.html
- 7 (Lunan)
The issue of how large ejecta escaping from the Moon can be is
discussed in
the Meteoritics paper. The "sparks" could not have been
large pieces of rock
distinguishable from the surrounding cloud of gas and dust by an
eyeball far
away.
The issue of lunar laser ranging and lunar libration is discussed
in the
Meteoritics paper. The relevant reference is Yoder (1981).
The inconsistencies between Gervase's text and what we know of
large
impacts, such as the phenomenon happening a dozen times or more,
is also
discussed in the Meteoritics paper. The relevant reference is
Nininger and
Huss (1977).
===========
(8) 100KM CIRCULAR FEATURE OFF THE COAST OF VIETNAM
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
Here is an extract from a web page about tektites that Hermann
Burchard
brought to my attention. Does anyone have more information about
the
'circular feature' mentioned below?
regards
Michael Paine
From Tektites by David Weir
http://www.geocities.com/~dweir/TEKTITES.HTM
...The largest known strewn field, encompassing the Austalasian
tektites, has yet to be identified with a particular impact
structure but it is suspected to be located on the Indochina
Peninsula.
However, recent gravity and topography data from Seasat and
Geosat has
identified an ~100 km circular feature off the coast of Vietnam
in the South
China Sea centered at 13.6° N., 110.5° E. that could prove to
be the
illusive crater.
===========
(9) AN OPEN INVITATION
From Leon Neihouse <neihouse@gwi.net>
Dear Benny,
The Alpha Space Foundation, a nonprofit organization operating in
the
asteroid/comet impact arena, plans to introduce the general
public to the
hazard through Exhibits set up in shopping malls. Members of this
forum are
cordially invited to review (see http://www.alphaspaceproducts.com/cbg.html)
and comment (to neihouse@gwi.net)
on this method.
Best regards,
Leon Neihouse
=========
(10) SNIPPETS FROM EDINBURGH EARTH SYSTEM PROCESSES CONFERENCE
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
Below are some extracts from abstracts of the conference that
Hermann
Burchard alerted me to.
regards Michael Paine
Earth System Processes Conference,
June 24-28, 2001, Edinburgh.
http://gsa.confex.com/gsa/2001ESP/finalprogram/
TRANSITIONS AND THE AMALGAMATION ANDFRAGMENTATION OF
SUPERCONTINENTS
DALZIEL, Ian W.D.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7902.htm
"A major puzzle lies in the role of apparently unrelated
extraterrestrial impacts at or close to the times of these
transitions."
THE IMPERFECT LINK BETWEEN VOLCANISM AND MASS EXTINCTION
WIGNALL, Paul B.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_5180.htm
"The most intriguing observation is that the "killing
efficiency" of
flood basalt eruptions declines rapidly after the Jurassic (if
the
Deccan Traps/K-T mass extinction link is disregarded in favour of
a more
compelling link with bolide impact)."
K-AR AND OXYGEN ISOTOPIC CONSTRAINTS OF ILLITIC CLAYS ON THE
TIMING AND
EVOLUTION OF THE WOODLEIGH IMPACT STRUCTURE, CARNARVON BASIN,
WESTERN
AUSTRALIA
UYSAL, I.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7365.htm
"Woodleigh is a recently discovered impact structure with a
diameter of
120 km, representing the third largest proven Phanerozoic impact
structure known after Morocweng and Chicxulub... Illite K-Ar ages
indicate a Late Devonian impact age, which coincides with several
other
impact events and a major global extinction in the Late Devonian
some
365 Ma ago... Woodleigh can be considered as a likely major
contributor
to this extinction."
THE TRIASSIC-JURASSIC BOUNDARY EVENT: SEARCHING FOR THE MECHANISM
TANNER, Lawrence H.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7665.htm
"The current view is that this event resulted from eruptions
of the
flood basalts of the Central Atlantic Magmatic Province (CAMP).
Frequently cited is the sudden increase in atmospheric CO2 from
outgassing during widespread eruptions, resulting in intense
global
warming. However, careful measurement of the carbon-isotope
composition
of pedogenic calcite from calcareous palaeosols of Late Triassic
to
Early Jurassic age fails to document any substantial change in
palaeo-pCO2 across the Triassic-Jurassic boundary. Suggestions of
large
increases in Early Jurassic palaeo-pCO2 from CAMP eruptions
appear to be
based on overestimates of the CO2 contribution from this
magmatism.
Alternative mechanisms for extinction related to volcanism remain
to be
explored more fully..."
CARBON ISOTOPE ANOMALY AND OTHER GEOCHEMICAL CHANGES AT THE
TRIASSIC/JURASSIC BOUNDARY: IMPLICATIONS FOR EXTINCTION SCENARIOS
PÁLFY, József
"Our results suggest that, similarly to other mass
extinctions, the
end-Triassic event was also associated with environmental
perturbations and changes in the global
carbon cycle...
It appears that the main isotope anomaly near the Tr/J boundary
was not
the result of a single event, but rather a culmination of a
period of
instability in the Earth systems, perhaps triggered by
large-volume
volcanism in the Central Atlantic Magmatic Province."
A JURASSIC SUPERPLUME EVENT AND ITS EFFECT ON THE EARTH SYSTEM
STOREY, Bryan C.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7614.htm
"Earth history is punctuated by short abrupt periods of
massive volcanic
eruptions due to the impact of deep-seated mantle plumes on the
Earth's
lithosphere..."
HYDROTHERMAL SYSTEMS: DOORWAYS TO EARLY BIOSPHERE EVOLUTION
FARMER, Jack D.
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7587.htm
"Subsurface hydrothermal systems may have also been a refuge
for
thermophilic microorganisms during late, giant impacts that
appear to have re-shaped
the early biosphere at the end of heavy bombardment."
MICROBIAL COMMUNITY OF HYDROTHERMS SPACE SUBJECTS AS A POSSIBLE
SOURCE
OF ORIGIN OF LIFE ON THE EARTH
ZHMUR, Stanislav
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_6482.htm
"Evidence obtained about litified remnants of carbonaceous
meteorites
microorganisms belonging to hydrothermal
mats(Zhmur,Gerasimenko,1999)
testifies to the high probability of the existance of
mummificated
remnants of microorganisms in carbonaceous meteorites (that was
confirmed by previous investigations) and to the possible
presence in
them of live substance which could be considered as panspermia
material.
Transportation of live Space substance to the Earth seems
real..."
THE SIMULATED SILICIFICATION OF BACTERIA: NEW CLUES TO THE MODES
AND
TIMING OF BACTERIAL PRESERVATION AND IMPLICATIONS FOR THE SEARCH
FOR
EXTRATERRESTRIAL MICROFOSSILS
TOPORSKI, Jan
http://gsa.confex.com/gsa/2001ESP/finalprogram/abstract_7608.htm
"The mechanisms of silicification under
laboratory-controlled conditions
and the implication for silicification in natural environments,
the search
for early Earth life and possible evidence of extraterrestrial
life are
discussed."
=========
(11) AND FINALLY: RESEARCHERS BLAME HUNGRY HOMO SAPIENS FOR LATE
QUATERNARY
MASS EXTINCTION
From the BBC News Online, 7 June 2001
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1375000/1375770.stm
By BBC News Online's Ivan Noble
Scientific research papers normally make dry reading, but this
one reads
almost like the start of a whodunnit:
"All Australian land mammals, reptiles and birds weighing
more than 100
kilograms perished in the late Quaternary," Richard G
Roberts of the
University of Melbourne and his colleagues write in the journal
Science.
And the question, of course, is indeed: Who did it? Who or what
could
possibly have caused the extinction of so many different
creatures in what
was, geologically speaking, a short period of time?
Investigations have been underway for more than a century and two
main
suspects have emerged.
Two suspects
The killer may have been a change in the climate, possibly the
onset of the
last ice age. Or it may have been that well-known offender with a
very long
record, Homo sapiens.
As detective film fans know, the case against the killer often
hinges on
establishing the time of death, and this time around is no
exception.
But for decades it has been difficult to establish when exactly
Australia's
giants died out. There are limits to the accuracy of radiocarbon
dating.
Now Richard Roberts and his colleagues have combined two other
dating
techniques to come up with more precise timings for a whole range
of fossils
from Australia and Papua New Guinea, which in times of lower sea
levels were
joined by land.
Key dates
And it looks like hard work for Homo sapiens' defence team:
Optical and uranium-thorium dating techniques both indicate that
the
extinctions are most likely to have taken place around 46,000
years ago.
With the last ice age at 19 to 23,000 years ago, the date is much
too early
for the climate to have been the culprit.
Instead, the evidence points to human culpability, since the
first humans
came to today's Australia around 56,000 years ago.
The scientists are not clear about the modus operandi of the
killer,
however.
Because of the margins of error, they cannot be sure whether
humans hunted
the giant lizards, birds and mammals to extinction, or whether
they simply
caused so much disruption to the ecosystem that the extinctions
came as a
consequence.
Either way, it looks like another case of destruction by humans.
"Our data are consistent with a human role in
extinction," the researchers
write.
US study
The Australian research is published at the same time and in the
same
journal as a study using computer predictions to try and discover
what was
responsible for similar mass extinctions in North America.
John Alroy of the University of California, Santa Barbara,
developed a
computer prediction taking into account different possible
numbers of humans
in ancient North America, their hunting ability, the degree of
competition
between species and the geographic dispersal of different
species.
His predictions matched closely to reality, correctly predicting
what
actually happened to 32 out of 41 prey species.
And not only was he able to predict which species would die out,
but also
when they would die out.
His conclusion was that the major extinctions in North America
occured
between 800 and 1,600 years after humans turned up around 13,000
years ago.
The destruction took place on a timescale that was, in geological
terms
instantaneous, but nevertheless slow enough in terms of human
generations
for those who unleashed it to be unaware of what they were doing.
Another indictment for Homo sapiens, but material at least for a
mitigation
plea.
Copyright 2001, BBC
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