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Date sent:        Wed, 07 Jan 1998 10:18:45 -0500 (EST)
From:             Benny J Peiser B.J.PEISER@livjm.ac.uk
To:               cambridge-conference@livjm.ac.uk
Priority:         NORMAL

CAMBRIDGE-CONFERENCE DIGEST, 7 January 1998
-------------------------------------------

(1) GENE SHOEMAKER'S REMAINS ON THEIR WAY TO FINAL RESTING PLACE

(2) EIGHTH IMPACT CRATER DISCOVERED IN FINLAND: TIMO NIROMA SUGGESTS
    SOME 3.000 MORE MAY YET TO BE FOUND ON EARTH

(3) RUSSIAN SCIENTISTS ANALYSE NUCLEAR DEVICES FOR PLANETARY DEFENSE

(4) COSMIC INSURANCE: WHAT IS THE CHANCE THAT THERE IS A LARGE
    ASTEROID WITH OUR NUMBER ON IT? ASKS DUNCAN STEEL

(5) WHAT IS THE ULTIMATE FATE OF A COMET?

(6) THE QUANDRANTIDS: A VERY YOUNG METEOR STREAM

(7) QUESTIONS ABOUT NEWLY DISCOVERED KUIPER BELT OBJECTS
 

===================================================================
(1) GENE SHOEMAKER'S REMAINS ON THEIR WAY TO FINAL RESTING PLACE

News Services
University of Arizona

From: Lori Stiles, UA News Services, 520-621-1877, lstiles@u.arizona.edu

Contact(s):
Carolyn Porco, 520-621-2390 or 520-299-8716,
carolyn@raven.lpl.arizona.edu (Jan. 6 -- Porco is traveling today.
She can be contacted tonight at the Casa De Playa Beach Hotel, 86
Ave. Isla Verde, San Juan, Puerto Rico, tel: 1-787-728-9779
fax:1-787-727-1334. After 3 p.m. Atlantic time (4 pm. EST) Jan. 7,
through Jan. 13, contact her at Marlin Quay, Gros Islet, St. Lucia;
tel: 758-452-0393; fax 758-452-0383)

Carolyn Shoemaker, 520-244-4350, gshoemaker@iflag2.wr.usgs.gov
(Jan 4-7 contact at the Royal Mansions 407-784-8484)

David Levy, 520-762-5685, dhlevy@lpl.arizona.edu, (Jan 4-7 contact
at Days Inn 407-783-4621, fax 407-799-5676)
--------------------------------------------------------------------

January 6, 1998

Lunar spacecraft carries ashes, special tribute to Shoemaker

WEB SITE -- http://condor.lphttpl.arizona.edu/~carolyn/tribute.html

There could be no finer tribute to the legendary planetary geologist
who said his greatest unfulfilled dream was to go to the moon.

Tonight, the ashes of Eugene M. Shoemaker are to be launched in a
memorial capsule aboard Lunar Prospector to the moon. The polycarbonate
capsule, one-and-three-quarters inches long and seventh-tenths inch in
diameter, is carried in a vacuum-sealed, flight-tested aluminum sleeve
mounted deep inside the spacecraft.

Around the capsule is wrapped a piece of brass foil inscribed with an
image of a Comet Hale-Bopp, an image of Meteor Crater in northern
Arizona, and a passage from William Shakespeare's enduring love story,
"Romeo and Juliet":

And, when he shall die,
Take him and cut him out in little stars,
And he will make the face of heaven so fine
That all the world will be in love with night,
And pay no worship to the garish sun.

Shoemaker was best known for his work on extraterrestrial impacts and
for his later collaboration with his wife, Carolyn, in the study and
discovery of comets. He was long a distinguished scientist with the
U.S. Geological Survey at Flagstaff, Ariz., where he established the
agency's astrogeology branch. He was killed July 18, 1997, in a car
accident in Alice Springs, Australia, during field research on impact
crater geology. Carolyn Shoemaker was injured in the accident.

"I don't think Gene ever dreamed his ashes would go to the moon,"
Carolyn Shoemaker said shortly before leaving to witness the Lunar
Prospector launch. "He would be thrilled."

The Shoemakers' children and their spouses, as well as a sister and
brother-in-law, are also at Cape Canaveral for the event.

"This is so important to us," Carolyn Shoemaker said. "It brings a
little closure, in a way, to our feelings. We will always know when we look
at the moon, that Gene is there."

Carolyn C. Porco, a planetary scientist at The University of Arizona in
Tucson, proposed and produced the tribute. She said, "The idea to give Gene
Shoemaker the moon as his final resting place came to me on July 19th , the
day after Gene died and the moment I read in the morning newspaper that his
body would be cremated."

It may be nothing short of a minor miracle that within only weeks,
Porco's inspired thought became reality. She quickly contacted the
Shoemaker family and NASA officials about the proposal. Given the
go-ahead, she designed and crafted the inscription in time to get it
and the capsule containing Shoemaker's ashes on the lunar spacecraft
before pre-flight testing.

Porco was a student of Shoemaker's when he was a professor and she was a
graduate student at the California Institute of Technology (Caltech). Field
trips that Shoemaker led into Meteor Crater and the Grand Canyon in northern
Arizona "are to this day among my most cherished memories," Porco said.
During the 1980s, Porco and Shoemaker were members of the imaging team for
Voyager, the mission to the outer planets. They also collaborated as
co-investigators on a science instrument proposal for the upcoming NASA
mission to Pluto.

"It was legend in the planetary science community that Gene had always
wanted to go to the moon as an Apollo astronaut and study its geology
firsthand," Porco said. "He said only last year, 'Not going to the moon and
banging on it with my own hammer has been the biggest disappointment in
life.' I felt that this was Gene's last chance to get to the moon, and that
it would be a fitting and beautiful tribute to a man who was a towering
figure and a pioneer in the exploration of the solar system," Porco said.

A health problem prevented Shoemaker from becoming the first geologist on
the moon. Instead, he helped select and train the Apollo astronauts in lunar
geology and impact cratering. He sat beside Walter Cronkite in evening
newscasts, giving geologic commentary during the moon walks. He was involved
in the pre-Apollo Lunar Ranger and Surveyor programs, and culminated his
lunar research as science-team leader on the 1994 Clementine mission.

The Clementine mission included a deliberate search for water near the poles
of the moon, Carolyn Shoemaker noted, but Clementine data did not settle the
question. The search for water at the lunar poles is a key goal of Lunar
Prospector, and that makes the tribute even more meaningful, she added.

Shoemaker, recipient of a 1984 honorary doctorate of science degree
from The University of Arizona, won many major honors. He was awarded
the National Medal of Science, the highest scientific honor bestowed by the
President of the United States, in 1992 by then-President George Bush.

Porco's striking thought ignited a rapid-fire e-mail exchange on July
19, a Saturday. She immediately sent a message to Tucson astronomer and UA
adjunct scientist David Levy, whose quoted comment about the cremation
sparked her idea. Porco told Levy, a close colleague and friend of the
Shoemakers, about the proposal and asked if he would help present it to
Carolyn Shoemaker.

Porco simultaneously sent an e-mail message to David Morrison of the
NASA Ames Research Center, inquiring about future lunar missions.
Morrison replied within hours that he had spoken with Lunar Prospector
Mission Director Scott Hubbard about the idea.

Levy quickly replied he thought it was an excellent idea and agreed
to ask Carolyn Shoemaker about it as soon as possible. He made his
first telephone call after the accident to Carolyn Shoemaker on July
20th, when she was just out of surgery at the hospital in Alice
Springs. Because there was so little time until Lunar Prospector
launch, which was then scheduled for September, 1997, Levy needed to
ask her about the proposed tribute during that call.

Levy confirmed with Porco that afternoon that when he told Carolyn
Shoemaker of the idea to put Gene's ashes on the moon, her first
reaction was, "Bless her." Carolyn Shoemaker told Levy she wanted
to discuss the proposal with the family when they arrived, but that
she liked the idea very much, and the more she thought about it,
the better she liked it.

"From 1948 to 1963, Gene's major goal was to go to the moon," Levy
said. "When Carolyn (Porco) came up with this idea, it was absolutely
the most wonderful thing she could have done."

Levy and the Shoemakers together in 1993 discovered Comet
Shoemaker-Levy 9, the spectacular comet that became unique in the
history of science when it was torn apart by and and crashed into
Jupiter in 1994. Levy has started work on Gene Shoemaker's biography,
which will be published by Princeton University Press.

Ten days after the accident, Porco had unofficial approval for the
proposal from NASA administrators.

By the end of August, a Phoenix firm, Universal Laser Systems, had
laser-engraved Porco's inscription design on the foil. She carried
the engraved foil with her to Flagstaff in late August, where she and
the members of the Shoemaker family placed the ashes in the capsule on the
grounds of the Shoemaker residence, in sight of the San Francisco Peaks.
From there, Porco flew the next day to NASA Ames Research Center where she
delivered the special payload to Hubbard -- just in time for installation
before the spacecraft was scheduled for spin-balancing.

Porco said she chose the Shakespeare passage for the inscription
because it expresses the love and devotion the Shoemakers had for each
other, and because it describes "what will now come to pass, that every
moon-lit sky will forever be made more beautiful by Gene's inspiring
presence."

She also chose for inscription a spectacular CCD image of Comet
Hale-Bopp, taken on April 14, 1997, with an 85mm camera lens by Steve
Larson of the UA Lunar and Planetary Laboratory. Comet Hale-Bopp blazed in
Earth's sky in the spring of the year that Shoemaker died, and it also was
the last comet that the Shoemakers observed together, Porco noted.

Porco also wanted to include the best photo of Meteor Crater in
northern Arizona, where Shoemaker had trained the Apollo astronauts. At
Carolyn Shoemaker's suggestion, Porco selected Gene Shoemaker's favorite
photo of the great crater, which shows the volcanic San Francisco Peaks and
several other important geologic features. It was taken by David Roddy and
Karl Zeller of the U.S. Geological Survey in Flagstaff.

Lunar Prospector was scheduled for launch during a 4-minute window that
began at 8:31 p.m. EST, or 6:31 p.m. MST, Jan. 5. Launch is now set for 9:28
EST, 7:28 MST, Jan. 6. After a 105-hour cruise to the moon, the spacecraft
will be placed in lunar orbit and begin a one-year mapping mission from 63
miles above the lunar surface. When its battery fails at the end of its
lifetime, an estimated 18 months or more from now, Lunar Prospector and its
special payload will crash on the moon.

======================================================================= (2)
EIGHTH IMPACT CRATER DISCOVERED IN FINLAND: TIMO NIROMA
    SUGGESTS SOME 3.000 MORE MAY YET TO BE FOUND ON EARTH.

from: Timo Niroma timo.niroma@tilmari.pp.fi

The eighth meteorite crater in Finland has recently been found. I have very
keenly followed the search here in Finland, because I insisted already in
late 60's as a newcome in Helsinki university, that Lappajarvi was a
meteorite crater. At that time there was no known meteorite crater here. So
I got laughed at. I had a 30-page treatise about the subject, but nobody
believed me. Only Ernst Palmen, later the president principal of Helsinki
University, was interested, but his comment was only: "Interesting, but how
can you be so sure?"

I had even a short English resume that I intended to send to Gene
Shoemaker, whose article in Scientific American (I think) made me very
excited. But I hadn't even visited Lappajarvi, I had and have no expertise
in geology, so I used other methods. First of all Lappajarvi is situated far
away of any volcanic areas, and in fact I got my idea while looking at the
Moon. Because Moon was so full of craters, I thought Earth should also have
about the same amount of hits, a little more because of its greater gravity
and a little less because of the protective shield of the atmosphere. So I
put a transparent paper on Moon and copied an area size of Finland. Then I
put the paper on the map of Finland and got a picture of what Finland would
look like if only all the craters would have preserved.

But the decisive evidence that made me sure about the character of
Lappajarvi came when I compared its size and shape or actually its
crossection profile on the other side with Moon craters and on the
other side with earthly volcanoes. The profile was very nearly
"lunatic" not that of any ex-volcano. And then there was this peak
a little side off the centre, an island named Karnansaari. And
then there was karnaite, a stone so hard, that there surely was
needed extraterrestrial force to make it.

But so disappointed was I that I burnt my paper and didn't send the
letter to Gene. In summer 1970 or 1971 I anyway took a tent and spend a few
days on the shores of Lappajarvi. But because I'm not a geologist, my only
contribution to science was to row on the lake. There was a stand kiosk and
I asked the salesman, if he did know that there was a meteorite crater
behind her. She laughed at me and said that I must be crazy. The schoolbooks
said it was an ex-volcano, it was scientifically proved.

Why do I tell all this. First of all Martti Lehtinen proved Lappajarvi
to be a meteorite crater in 1974 in his doctoral dissertation. But a
layman in the field can do his/her thinkwork with Occam's razor.

The need arises from the fact that if we compare the surface area of
Finland with the whole global area, there should be evidence of about
10,000 meteor craters. And only 170 have thus far been found. Obviously
there are nearly none found in the oceans, but 3,000 should still be found
on the continents, if the search be as intensive as it is here in Finland.
Actually more, because of the 8 craters so far found here, 7 are in the
southern part of Finland and only the newest one is in the borderline
between southern and northern Finland. But none in Lappland. There must be
one in Petsamo, because of the tremendous amount of nickel found there. And
here is a prediction: the southern part of the Dead Sea is a meteorite
crater. Take a look at the map and especially the cross-section. The story
of the hit is told, I think, in Genesis.

The coordinates of the new (old) crater are 28E, 65N. It is in a place
named Taivalkoski, which is situated in Kuusamo, the middle-east part
of Finland. The crater lake which before this hadnt even a name, has
now been named Saarijarvi (A little bad choice, because we have another
Saarijarvi souther, which is famous in Finnish history). But so do we have
about ten Pyhajarvi, and so on. Saarijarvi, by the way, means a lake with an
island.

The diameter of the crater is 1.5 km (The lake is a little smaller).
The age estimate makes it some 600 million years old. The totally
crashed stone area begins 157 m below the lake's surface. There is 140 m
clay (kaoline) between the bottom of the lake and the area destroyed by the
meteorite. In fact those who drilled the lake bottom were not searching for
a meteorite crater but diamonds. The crater is now investigated in
cooperation between Helsinki University and Munster University (Germany).

The other seven meteorite craters in Finland are those three found in
70's and 80's: Lappajarvi, Saaksjarvi and Soderfjarden and the four
found earlier in 90's: Iso-Naakkima, Suvasvesi, Lumparn and
Karikkoselka.

Timo Niroma timo.niroma@tilmari.pp.fi

===========================================================================
(3) RUSSIAN SCIENTISTS ANALYSE NUCLEAR DEVICES FOR PLANETARY
    IMPACT DEFENSE

A. S. Alekseev*), Y. A. Vedernikov, L. I. Velichko, V. A. Volkov:
The rocket conception of cumulative impact defense of the earth against
dangerous space objects. INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 1997,
Vol.20, No.1-5, pp.1-12

*)RUSSIAN ACADEDMY OF SCIENCE, CTR COMP, NOVOSIBIRSK 630090, RUSSIA

Asteroids and comets with trajectories intersecting of the Earth
represent a danger to our planet. Possible ways to prevent a dangerous
object from colliding with Earth are splitting or deflecting its trajectory.
For that purpose nuclear explosive devices with power up to 10-20 Megatons
are proposed to be used. The report based on statistical data processing
embracing over 100 potentially dangerous asteroids gives a substantiation of
required performances of the Space Rocket Interception Complex - the basic
component of the Earth Protection System. The calculated time of
interception and required initial velocity, depending on the time left until
collision and efficiency of the available nuclear device, are presented. The
report shows the possibility of creating an interception complex consisting
of a space interceptor with a nuclear explosive device, a booster, a
launch-vehicle and supporting systems.

=====================================================================
(4) COSMIC INSURANCE: WHAT IS THE CHANCE THAT THERE IS A LARGE
    ASTEROID WITH OUR NUMBER ON IT? ASKS DUNCAN STEEL

from: NEW SCIENTIST, 3 January 1998

Planet Earth has been struck many times by asteroids and comets,
with calamitous consequences. Just ask the dinosaurs. If you're
concerned about the environment, think of the effects a
2-kilometre asteroid would have. For starters, it would create a
crater 30 kilometres across and the energy released by the impact
would be equivalent to a million megatonnes of TNT - more than
10,000 times the power of the larges hydrogen bomb ever tested.

Be clear, though, that this is a mere firecracker compared to the
20-kilometre beast that sculpted a 240-kilometre-wide crater in
Mexico 65 million years ago, suppossedly killing off the
dinosaurs. Just 2 kilometres, though, is the threshold asteroid
size at which the impact explosion would produce sufficient
noxious oxides of nitrogen to cause a global catastrophe. The
spectacluar crash of Comet Shoemaker-Levy 9 into Jupiter in 1994
allowed scientists to test models of cosmic impacts. A 1- or
2-kilometre asteroid impact would kill over a quarter of the
world's population.

There are many more sand grains on a beach than large pebbles.
Similarly, there are more small rocks in space than large ones.
Massive asteroids strike home only once every 50 million to 100
million years, but smaller projectiles hit the Earth more often.
The rate is about once every 500,000 years for 2-kilometre objects
and every 100,000 years for 1-kilometre objects. Such an impact
would spell the end of civilisation as we know it.

There's a 1 in 1000 chance, then, that within the next century,
humanity's progress will be rudely interrupted by such a
cataclysm. Should we be worried? What should we do? It all reduces
to a question of money. How much should we spend? It's the
economics of Armageddon.

Imagine you want comprehensive insurance cover for your car. The
insurance company assesses the past performance of drivers of your
age, sex, car model, and so on, and from such data it calculates
an "annual expectation of loss" (AEL). If this is £200, then you
might be offered cover for £350 to take into account the paperwork
and profit. The premium must be higher than the company's AEL,
otherwise it would quickly go bankrupt. Of course, it does not pay
out £200 for each driver every year: of a thousand drivers,
perhaps two have total write-offs costing £20,000 each, another
hundred sustain minor demage, but the majority make no claim at
all.

Infrequent events for which there is no definite precedent are
more troublesome. The early failure rate estimate for the space
shuttle of around 2 per cent meant that the disastrous 25th flight
(the Challenger explosion) was near the expectation. For many
natural disasters, the historical record is of little use. For
instance, there were no skyscrapers in Tokyo when the last great
earthquake occurred there, so it's difficult to estimate the
economic damage a big quake would do.

Bearing this in mind, let's estimate the AEL for the European
Union (population of 400 million, say) due to asteroid impacts.
First, how much is a human worth? The mean lifetime earnings of a
EU worker are close to £1 million, and the British government
spends about that much on road safety to avoid each notional
traffic death, making it a reasonable estimate for the value of a
human life in the EU.

If the annual probability of a 1-kilometre impact calamity is 1 in
100,000 and such an impact would kill a quarter of Europe's
inhabitants, then the AEL for the EU alone is: £1,000,000 x
400,000,000 x 0.25 x 0.00001 = £1 billion. That's a large sum, but
in reality the AEL is higher because such a catastrophe would
trigger a global economic collapse and devaluation of assets built
up over the centuries - a can of beans would be worth more than a
Van Gogh or a Matisse.

If it makes you happier to think only of the 2-kilometre impactor
every 500,000 years, then fine. But the AEL ist still hundreds of
millions of pounds (or ecus). And don't forget we're only
considering the infrequent globally catastrophic impacts. It's a
bit like only worrying about car write-offs, ignoring the more
frequent smaller accidents which cost a lot to put right.

The amount of money we need to spend to answer the question "Is
there an asteroid due to hit us soon?" is far less than the
liability estimated here. Not to carry out the necessary search
programme is foolhardy, and irresponsible. It's almost like
turning down car insurance offered at £1 a year as being too
costly.
---
DUNCAN STEEL is vice-president of The Spaceguard Foundation, which
aims to carry out the survaillance programme needed to discover
whether an asteroid or comet is headed our way within the next
century.

======================================================================= (5)
WHAT IS THE ULTIMATE FATE OF A COMET?

A. Coradini*), F. Capaccioni, M. T. Capria, M. C. DeSanctis, S.
Espinasse, R. Orosei & M. Salomone: Transition elements between comets and
asteroids. Part1: Thermal evolution models. ICARUS, 1997, Vol.129, No.2,
pp.317-336

*)IAS REPARTO PLANETOL, VLE UNIV 11, I-00185 ROME, ITALY

What is the ultimate fate of a comet? Excluding impacts with other
bodies, two possibilities are foreseen: either long-lasting activity,
accompanied by nucleus reduction, or the formation of a stable crust
that inhibits dust emission and strongly reduces volatile emissions. In the
first case the comet could disintegrate, whereas in the second case it could
become dormant or extinct, assuming an asteroidal appearance; in both cases
the comet could be reactivated. In this paper we present results of a comet
evolution model trying to establish the conditions under which the nucleus
becomes dormant or extinct and under which it continues its activity up to
the consumption of the icy material. Our nucleus model is composed of a
mixture of ices of water, CO2, and CO and dust particles. The H2O ice can be
either amorphous or crystalline; the solid matrix is assumed to be porous.
The evolution of the body is determined by the solar energy reaching its
surface and by the heat transfer in the interior. The propagation of the
heat through the nucleus is modeled by means of the heat transfer and gas
diffusion equations, coupled via the condensation-sublimation terms that are
seen as sinks or sources of energy and matter, respectively. Particular
attention is given to the variations of porosity and to the changes in
composition of the superficial layers due to sublimation-condensation
phenomena, to gas diffusion processes through the pore system, and to the
ejection of dust particles. At the beginning of the evolution of the nucleus
the crust is never present and the interior of the comet is not
differentiated. We have seen that the evolution can proceed essentially in
two ways: (1) if the body is dark and rich in volatiles and the dust grains
are fluffy, then the upper layers are usually removed at the same rate at
which the CO2 upper boundary sinks; (2) in the opposite case, sometimes a
dusty crust is formed, sometimes not, but in any case the CO2 interface
sinks deeply. We conclude that in the first case the body will remain active
for several orbits, while in the second case the gradual reduction of any
activity can produce a dormant or extinct comet, maybe with the appearance
of an asteroid.

-------

A. Coradini*), F. Capaccioni, M. T. Capria, M. C. DeSanctis, S.
Espinasse, R. Orosei, M. Salomone & C. Federico: Transition elements
between comets and asteroids. Part 2: From the Kuiper belt to NEO
orbits. ICARUS, 1997, Vol.129, No.2, pp.337-347

*)IAS REPARTO PLANETOL, VLE UNIV 11, I-00185 ROME, ITALY

In this paper we study the evolution of a comet nucleus taking into
account its orbital evolution. It is assumed that the nucleus undergoes
several close encounters with Giant Planets and its final orbit is that of
the near-Earth object 4015 Wilson-Harrington. In paper I we presented
results of a comet evolution model establishing the conditions under which
the nucleus becomes dormant or extinct; we also identified a range of
physical conditions leading to long-lasting activity that inexorably lead to
the consumption of the icy material. The assumption in paper I was that the
nucleus model is composed of a mixture of ices of water, CO2, and CO and
dust particles; the H2O ice is initially crystalline. In this paper we
analyze if the initial status of ice, the presence of CO, and the spin
period affect the evolutionary history of the body, and if part of the
original material is preserved in the inner part of the nucleus when the
comet becomes a short-period comet.

===============================================================
(6) THE QUANDRANTIDS: A VERY YOUNG METEOR STREAM

P. Jenniskens*), H. Betlem, M. deLignie, M. Langbroek, M. vanVliet:
Meteor stream activity. The Quadrantids, a very young stream. ASTRONOMY AND
ASTROPHYSICS, 1997, Vol.327, No.3, pp.1242-1252

*)NASA, AMES RESEARCH CENTRE, MAIL STOP 239-4, MOFFETT FIELD, CA, 94035

This paper presents the first large set of precisely reduced orbits of
Quadrantid meteoroids. These orbits were ob-l rained from photographic
observations during the 1995 return of the Quadrantid stream. The orbits
refer to the main peak of the activity curve, with an unidentified few being
part of a broad background component. The measured dispersion of orbits is
less than from previous data obtained by less accurate techniques. In
combination with existing stream models, we conclude that the main component
is only about 500 years young, much less than the 5000-7500 year age that
was widely assumed before. This main peak is now interpreted as an
''outburst'', with an evolution history similar to other near-comet type
outbursts, while the background is thought to be the classical ''annual''
dust component. The stream does not originate from comet 96P/Machholz.
Rather the parent object may be hiding as an asteroid-like object in a
high-inclination orbit. An estimate of that orbit is given.

==================================================================
(7) QUESTIONS ABOUT NEWLY DISCOVERED KUIPER BELT OBJECTS

M. E. Brown*), S. R. Kulkarni, T. J. Liggett: An analysis of the
statistics of the Hubble Space Telescope Kuiper belt object search
ASTROPHYSICAL JOURNAL, 1997, Vol.490, No.1 Pt2, pp.L119-L122

*)CALTECH, DIVISION GEOLOGY & PLANETARY SCIENCE, PASADENA, CA, 91125

We calculate statistical limits to the detection of Kuiper belt objects in
the Hubble Space Telescope (HST) data of Cochran et al., in which they
report the discovery of a population of Halley-sized objects in Pluto-Like
orbits. Detection of a population of faint objects in these data is limited
by the number of false objects that appear owing only to random noise; the
number of real objects must exceed the uncertainty in the number of these
false objects for the population to be observable. We determine the number
of false objects expected owing to random noise in the data of Cochran et
al. by measuring the pixel-to-pixel noise level in the raw HST data and
propagating this noise through the detection method employed by Cochran et
al. We find that the uncertainty in the number of false objects exceeds by 2
orders of magnitude the reported number of objects detected by Cochran et
al. The detection of such a population of Halley-sized Kuiper belt objects
with these data is therefore not possible.

CCCMENU CCC for 1998