MARSBUGS:  
The Electronic Exobiology Newsletter 
Volume 3, Number 15, 13 November, 1996.

Editors:

David Thomas, Department of Biological Sciences, University of 
Idaho, Moscow, ID, 83844-3051, USA, thoma457@uidaho.edu.

Julian Hiscox, Microbiology Department, BBRB 17, Room 361, 
University of Alabama at Birmingham, Birmingham, AL 35294-2170, 
USA, Julian_hiscox@micro.microbio.uab.edu.

MARSBUGS is published on a weekly to quarterly basis as warranted 
by the number of articles and announcements.  Copyright of this 
compilation exists with the editors, except for specific 
articles, in which instance copyright exists with the 
author/authors.  E-mail subscriptions are free, and may be 
obtained by contacting either of the editors.  Contributions are 
welcome, and should be submitted to either of the two editors.  
Contributions should include a short biographical statement about 
the author(s) along with the author(s)' correspondence address.  
Subscribers are advised to make appropriate inquiries before 
joining societies, ordering goods etc.  Back issues may be 
obtained via anonymous FTP at:  ftp.uidaho.edu/pub/mmbb/marsbugs.

The purpose of this newsletter is to provide a channel of 
information for scientists, educators and other persons 
interested in exobiology and related fields.  This newsletter is 
not intended to replace peer-reviewed journals, but to supplement 
them.  We, the editors, envision MARSBUGS as a medium in which 
people can informally present ideas for investigation, questions 
about exobiology, and announcements of upcoming events.  
Exobiology is still a relatively young field, and new ideas may 
come out of the most unexpected places.  Subjects may include,  
but are not limited to:  exobiology proper (life on other  
planets), the search for extraterrestrial intelligence (SETI), 
ecopoeisis/ terraformation, Earth from space, planetary biology, 
primordial evolution, space physiology, biological life support  
systems, and human habitation of space and other planets.
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1)	ASTEROID HIT AT DEADLY OBLIQUE ANGLE 65 MILLION YEARS AGO 
	From The Brown University News Bureau

2)	STARDUST COMET MISSION PASSES KEY MILESTONE
	JPL release

3)	EARLIEST LIFE ON EARTH
	Communicated by Steve Mojzsis 

4)	FUTURE MOON, MARS EXPLORATION PLANS TO BE REVEALED
	Meeting announcement
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ASTEROID HIT AT DEADLY OBLIQUE ANGLE 65 MILLION YEARS AGO 
From The Brown University News Bureau

A new study says the asteroid that struck Earth 65 million years 
ago and wiped out the dinosaurs was particularly deadly to North 
America because it hit the Yucatan peninsula from the southeast 
at a 20- to 30-degree angle, spreading the devastating impact of 
its energy northwest.

The oblique angle of the asteroid's contact with Earth coupled 
its impact energy with that of the atmosphere and planetary 
surface to send waves of ground-hugging, vaporous fireballs 
onward, the study says.  This resulted in an extinction intensity 
most severe downrange of the impact in North America.  The study 
suggests one rationale for the dire consequences of such an 
impact--the severity of extinctions that result from an object's 
impact on Earth may reflect the incoming object's angle.

"This finding may help us determine what other impacts did to 
Earth in the past and what they may do in the future," said Peter 
Schultz, professor of geological sciences at Brown University.  
Schultz and Steven D'Hondt, professor of oceanography at the 
University of Rhode Island, are co-authors of the study in the 
November issue of the journal Geology.

The researchers suggest that the relatively low angle of the 
Yucatan impact propelled a ballistic fireball downrange into 
North America.  The fireball carried a two-mile-deep layer of 
vaporized rock and other material sheared off the Yucatan.  The 
killing zone of matter cascaded through the atmosphere at near 
orbital speed, across North America and eventually around the 
globe.

"It was like a nuclear explosion taken north on a jet-powered 
sleigh ride," Schultz said.  "This was indeed the day the Earth 
shook."

As evidence, the researchers show that the horseshoe-shaped 
Yucatan crater matches the structure of craters on the moon and 
Venus that were created when objects struck those heavenly bodies 
at oblique angles.  Venus's thick atmosphere holds in place gases 
emitted from a crater after an impact.  The researchers studied 
images of these corked-in Venusian vapors, which show that 
gaseous material is propelled in waves downrange after an object 
strikes a planetary surface at an oblique angle.

Schultz used a high-powered gun to recreate the dynamics of an 
object striking Earth's surface at a 20- to 30-degree angle.  The 
experiment produced horseshoe-shaped craters, while high-speed 
film captured gas and materials jettisoned downrange.

The researchers said that biological evidence appears to support 
their oblique-impact hypothesis. North America, the first region 
to experience the fireball, had the most severe extinctions of 
plants.

After the devastation, ferns dominated the flora of central North 
America.  Ferns accounted for 70 to 100 percent of the spore- or 
pollen-producing plants in the region after the impact, compared 
with only 10 to 40 percent before it.  At the base of the food 
chain, plants are considered sensitive indicators of 
environmental devastation.  Because ferns reproduce through the 
use of hardy spores, the plants are regarded as key flora in 
colonizing the site of a natural disaster.

Plants in parts of the world not downrange from the impact took a 
lesser hit from the corridor of incineration.  For example, 
several ancient evergreen trees found in North America before the 
impact, but not after, still grow in parts of Australia and South 
America.  Modern relatives of these trees, often called 
"primitive conifers," include the Norfolk Island pine, Chilean 
monkey puzzle and Wollemi pine.

"The basic point of the study is that we can determine the impact 
angle of this object and that the angle matters," D'Hondt said.  
Most scientists study the aftermath of collisions that caused 
Earth's craters as if objects struck the planet at 90-degree 
angles, or from directly overhead.  But such vertical impacts are 
very rare.

An oblique angle of impact may have more deadly global 
consequences than a vertical impact, because an oblique impact 
should release a greater fraction of impact energy to the 
atmosphere and surface target, said Schultz and D'Hondt.

"The study also underscores the point that regional repercussions 
can be expected from an Earth-object impact, something scientists 
have rarely considered in previous studies of this 65-million-
year-old event," D'Hondt said.


A link is provided for downloading the color transparencies in 
this release (see 2nd paragraph in heading).  The URL is:
http://www.brown.edu/Administration/News_Bureau/1996-97/96-
041g.html
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STARDUST COMET MISSION PASSES KEY MILESTONE
JPL release

NASA's Stardust mission, which will gather samples of dust as it 
flies by a comet and return them to Earth, has passed a key 
milestone with completion of its preliminary design review.  The 
project team got a thumbs up on its mission plans from an 
independent review board appointed by the space agency. Dr. 
Wesley T. Huntress, NASA's associate administrator for space 
science, confirmed the review board's conclusion that the project 
is ready to move forward into its development phase.

"This tells us we are fully on track, ready to meet our schedule 
and cost control constraints," said Stardust Project Manager Ken 
Atkins of NASA's Jet Propulsion Laboratory, Pasadena, CA.

Stardust is the latest in NASA's series of Discovery missions, 
which teams NASA with industry and universities to launch low-
cost spacecraft in a short time frame with highly focused 
scientific goals.  Successful completion of the review marks the 
end of the mission's concept definition phase--known in the 
aerospace industry as Phase B--and the start of design, 
development and fabrication, known as Phases C and D.

NASA is committing nearly $118 million for Stardust development, 
with an additional $37 million necessary for mission operations.  
The next major review will come in June 1997 with a critical 
design review to confirm that design is complete and subsystems 
are on schedule for spacecraft integration, scheduled to begin in 
February 1998.  Launch is planned for February 1999.

During its journey through space, Stardust will loop twice around 
the Sun to collect interstellar dust particles before it flies 
past Comet Wild-2 in 2004.  Stardust will gather dust and other 
materials spewed from the comet's tail and return the samples to 
Earth in 2006 for scientific study.  The mission will be the 
first ever to return material from a solar system object other 
than the Moon.

As the most primitive bodies in the solar system, comets hold 
great fascination for scientists, who believe they may reveal 
vital clues about the birth of the planets and the formation of 
life.  The cosmic leftovers from planet formation, comets are 
rich in organic compounds and may have played a key role in the 
development of early life on Earth.

Mission planners faced a tough challenge--how to capture comet 
dust as it whizzes by the spacecraft about seven times faster 
than a bullet fired from a rifle.  The answer came in the form of 
aerogel, a sponge-like silica gel in which 99 percent of the 
volume is empty space.  When a speck of comet dust hits the 
aerogel, it slows down gradually and comes to a stop, burying 
itself safely in the flexible material.  Because aerogel is 
mostly transparent, scientists can trace the tracks to retrieve 
the comet dust.

The minuscule bits of cargo will be stored in a capsule designed 
to separate from the spacecraft's main body and descend into 
Earth's atmosphere, landing in Utah.  The main spacecraft will 
continue in orbit around the Sun indefinitely.

Scientists are eagerly awaiting this opportunity to "get their 
hands on" particles of comet dust.  "We guarantee the return of 
1,000 particles larger than one-quarter the size of a human 
hair," said Stardust Principal Investigator Dr. Don Brownlee of 
the University of Washington.  "Most likely there will be many 
additional particles of various sizes."

Brownlee leads the team collaborating on Stardust.  The 
spacecraft and sample return capsule are being built by Lockheed 
Martin Astronautics in Denver, CO.  The mission is managed by 
NASA's Jet Propulsion Laboratory in Pasadena for NASA's Office of 
Space Science, Washington, DC; JPL is also developing the 
spacecraft's navigational camera.  Stardust's cometary and 
interstellar dust analyzer instrument is provided by Jochen 
Kissel through the Max Planck Institute in Germany.
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EARLIEST LIFE ON EARTH
Communicated by Steve Mojzsis 

Evidence for life on Earth more than 3,800 million years ago is 
presented in a report on page 55 from Gustaf Arrhenius of the 
Scripps Institution of Oceanography in La Jolla, California and 
colleagues.  Analysis of the oldest known sedimentary rocks, 
associated with a 3,800-year-old "banded iron" formation in 
Greenland, reveal tiny inclusions of carbonaceous material sealed 
within grains of apatite (calcium phosphate).  The carbon is 
isotopically "light," that is, the "heavy" isotope of carbon, 
carbon 13, is less abundant, relative to carbon 12, than one 
would expect had the carbon been processed by known inorganic 
processes.  The metabolic activities of living organisms are 
known to fractionate carbon isotopes in this way.  Indeed, no 
inorganic process is known that can mimic this distinctive 
signature of life. This, together with the setting (within 
apatite grains) has all the hallmarks of past life.

The Greenland rocks, which show signs of metamorphism consonant 
with their great age, bear no actual "fossils" of bacteria.  The 
oldest known fossils come from the Apex Cherts of Australia, and 
are about 3,500 million years old (see Schopf, J. W., Science 
260, 640-646; 1993).  The new finds take the record of life right 
back to the formation of the earliest known sedimentary 
sequences.  This raises challenging questions about the speed of 
the evolution of life, just two hundred million years or so after 
the young Earth had been subjected to a meteoritic bombardment of 
an intensity sufficient to sterilize the planet.

John M. Hayes of the Woods Hole Oceanographic Institution, Woods 
Hole, Massachusetts discusses the research in an accompanying 
News and Views article.

Full text of the report will be available online from midnight 
Wednesday 6 November: see Nature's web page at 
http://www.nature.com or http://www.america.nature.com
CONTACT:  Gustaf Arrhenius tel +1 619 534 2961, fax +1 619 534 
2961, email arrhenius@ucsd.edu; John M. Hayes tel +1 508 289 
2585; fax +1 508 457 2183; email jhayes@whoi.edu
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FUTURE MOON, MARS EXPLORATION PLANS TO BE REVEALED

Hotels on the Moon?  What business ventures await entrepreneurs 
as Earth's Moon becomes a new site for "ROI":  Return On 
Imagination?

Is there presently life on Mars?  What will the next wave of 
robot explorers find?  Can a 21st century Mars be transformed 
into a second home for humanity?

International Space Enterprises (ISE) and the National Space 
Society (NSS) announce the Third Annual International Lunar and 
Mars Exploration Conference, to be held in San Diego, California 
on November 17-20.  Experts from industry, entrepreneurial firms, 
universities and NASA will review the promise of a rejuvenated 
space agenda for the 21st century in up- to-the-minute talks and 
discussion.

Topics include establishing Lunar Base-1; low-cost robotic and 
human missions to Mars and the search for life; marketing space 
for commercial benefit; space tourism; and 21st century space 
transportation.

Among the speakers:  moonwalker, Apollo 17 astronaut Harrison 
Schmitt on future human presence on the Moon and Mars; Robert 
Zubrin, author of The Case for Mars--The Plan to Settle The Red 
Planet and Why We Must; Kenji Takaji & Shinji Matsumoto from 
Japan's Shimuzu Corporation on energy supplies for a lunar base; 
Michael Lawson of Space Marketing, Inc.; space tourism expert, 
Peter Diamandis of the X-Prize Foundation; John Kerridge, UCSD 
expert on the search for life on Mars; and Lockheed Martin's 
Jerry Rising to detail the X-33 project, stepping stone to 
single-stage-to-orbit rocketry.

In a unique public demonstration, ISE will invite conference 
participants to view and operate the robotic Mars Seeker, a new 
prototype of a rover ISE hopes to deliver to Mars on a 
commercially financed, international voyage.  The Mars Seeker 
prototype will be the centerpiece of a permanent interactive 
exhibit at NASA's Kennedy Space Center beginning in December.

The conference, to be held at the beautiful Hyatt Islandia Hotel 
on San Diego's Mission Bay, will convene top lunar and planetary 
scientists and engineers.

For registration details about the conference, or press 
information, please contact:  Greg Nemitz of ISE [phone:  (619) 
637-5773, fax:  (619) 637-5776]; via e-mail:  isehq@aol.com] or 
call the National Space Society at (202) 543-1900.
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End Marsbugs Vol. 3, No. 15.


