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Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: JPL Recruits Two Experts To Help Hunt For New Planets and Life
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Jane Platt
FOR IMMEDIATE RELEASE March 5, 1998
JPL RECRUITS TWO EXPERTS TO HELP HUNT FOR NEW PLANETS AND LIFE
Two newly-arrived scientists at NASA's Jet Propulsion
Laboratory will play a key role in the search for planets around
other stars and the hunt for life beyond Earth. The appointments
highlight a new JPL initiative to unite scientists from various
disciplines, such as biology and astronomy, to study the
evolution of planets and life in the universe.
Dr. Didier Queloz, a Swiss astronomer who co-discovered the
first known planet around a star similar to our Sun, is a
distinguished visiting scientist at JPL for the next year and a
half. Dr. Kenneth Nealson has joined JPL as a senior researcher
in astrobiology, a new field whose goal is to understand how
planets and life co-evolve.
While at JPL, Queloz will continue his search for planets
and help the Lab develop sophisticated search technologies. His
work will benefit NASA's Origins Program, a series of planned
missions to study the formation of galaxies, stars, planets and
life. The program has gained momentum from discoveries by Queloz
and, subsequently, other astronomers, of several planets orbiting
stars beyond our Sun. Many scientists believe this raises the
odds that an Earth-like planet exists with suitable conditions
for life.
Queloz, a Swiss citizen, received his degree in physics in
1990 from the University of Geneva and worked on his doctoral
thesis at Geneva Observatory with Professor Michel Mayor from
1991 to 1995. Using the French Elodie telescope in Haute
Provence, France, they looked for signs of a Doppler shift in
nearby stars. As a star moves closer and then farther away from
Earth, the star's color shifts from red to blue. By detecting
this motion, astronomers can infer that the star is being tugged
by gravity from an orbiting planet.
"Back then, these experiments were considered a bit nutty,"
recalled Queloz. When Queloz and Mayor first detected a Doppler
shift from the star 51 Pegasus, Queloz said their first reaction
was, "We'd better check our instruments."
Even after they verified the instruments' accuracy, Queloz
and Mayor spent several weeks monitoring 51 Pegasus to confirm
the discovery. In July of 1995, they were confident enough to
buy a large cake and hold a celebration party in the south of
France for family and friends. Queloz and Mayor formally
announced their discovery, a Jupiter-sized planet orbiting 51
Pegasus, at an October 1995 scientific meeting in Florence,
Italy.
Queloz has received several honors, including the Swiss
Society for Physics' Balzers Award, the Bioastronomy Medal from
the International Astronomical Union, Commission 51, and a Best
Thesis in Science honor from a Swiss corporation, Vacheron
Constantin.
Queloz is continuing his hunt for new planets with the
Elodie telescope and its twin, Coralie, a Swiss telescope in La
Silla, Chile. But he and other astronomers face great challenges
in finding new and better ways to detect planets more like Earth.
Current techniques allow only for the detection of giant,
Jupiter-sized planets, which are considered unlikely candidates
for life.
While at JPL, Queloz will share his planet-finding
experience with engineers who are designing more advanced
technologies. Queloz is using a testbed interferometer at
Caltech's Palomar Observatory to run tests on stars and prepare
for an observing program. This work will help pave the way for
other Origins projects, including the W.M. Keck Observatory
interferometer in Hawaii, the Space Interferometry Mission, and
the Terrestrial Planet Finder, all being planned by NASA.
Interferometry combines and processes light from several
telescopes to simulate a much larger telescope, and holds great
promise as a tool in the search for Earth-sized planets. "I'd
like to play a role in future exploration by helping to define
interferometry techniques," Queloz said.
During his stay at JPL, Queloz is living in Pasadena with
his wife and their two children.
Until very recently, an astronomer like Queloz would have
had little if any interaction with a biological scientist like
Dr. Kenneth Nealson. But various disciplines, such as astronomy,
geology, biology and chemistry, are joining forces to study the
development of life on Earth and the prospects of life elsewhere.
Therefore, the work of scientists like Nealson and Queloz is
converging to form a broad, interdisciplinary approach.
"After all," said Nealson, "life is not a simple system and
no science operates in a vacuum. Younger students are studying
several disciplines to gain a more comprehensive view."
Nealson is part of this new wave of scientific training, as
a geobiology teacher and faculty associate in Caltech's geology
and planetary sciences division. At JPL, a division of Caltech,
Nealson has been appointed to head a new astrobiology unit.
Nealson said over the next few years, his astrobiology group will
develop an understanding of the way life and planets have
evolved, and will define the signatures of life.
"Not many foolhardy souls have ventured into this area,"
Nealson said. "After all, how can you find life if you don't
know what you're looking for? This is a very, very important
problem to be solved because right now we're not sure how to
distinguish life from non-life. Our goal is to develop tools to
make that distinction clearly."
In recent years, microbiologists have made startling
discoveries about the hardiness of life on Earth, studying living
organisms in thermal vents, acid lakes and other unlikely
environments. Nealson pointed out, "This has opened the eyes of
scientists to the notion that life could exist under seemingly
inhospitable conditions on other planets."
Astrobiologists will also study changes in Earth's chemical
composition over billions of years. They will then apply this
knowledge to other planets to look for "chemical signatures" that
might indicate that life has existed or could exist there.
Nealson said astrobiology will be useful for numerous space
missions, including the Mars sample return mission, scheduled to
bring back Martian rocks in the middle of the next decade.
Astrobiology will also benefit the Origins Program's Terrestrial
Planet Finder, which will look for Earth-like planets around
other stars and hunt for signs of life-sustaining chemicals.
Nealson said astrobiological studies may prove valuable in the
study of Jupiter's moon, Europa, which may have liquid oceans
under its frozen surface. This icy moon is currently being
studied by NASA's Galileo Europa Mission, and a new Europa
Orbiter has a planned launch in 2003.
Originally from West Liberty, Iowa, Nealson got his bachelor
of science degree in biochemistry in 1965 from the University of
Chicago. He earned his Ph.D. in microbiology from the University
of Chicago and did postdoctoral studies at Harvard University.
Nealson taught at Scripps Institution of Oceanography, San Diego,
CA, and at the Center for Great Lakes Studies, University of
Wisconsin, Milwaukee, WI. His honors include the Guggenheim
Fellowship for Sabbatical Leave in 1981, and an appointment as an
elected fellow in the American Academy of Microbiology, which he
received in November 1993.
Nealson and his wife live in South Pasadena, CA.
#####
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=SANA=
Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: * SpaceNews 09-Mar-98 *
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SB NEWS @ AMSAT $SPC0309
* SpaceNews 09-Mar-98 *
BID: $SPC0309
=========
SpaceNews
=========
MONDAY MARCH 9, 1998
SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It
is published every week and is made available for non-commercial use.
* HAM RADIO AND AMSAT FEATURED IN NY TIMES *
AMSAT-NA Executive Vice President Keith Baker, KB1SF, has reported that
AMSAT is included in a feature article about Amateur Radio and the Internet
in the Thursday, March 5th edition of the New York Times newspaper. The
article, written by John Verity, a New York Times feature writer, is
contained in a recently added section of the paper called "Circuits".
The story examines the links between the Amateur Radio hobby and the
Internet, and how Amateur Radio and AMSAT have both expanded and exploited
those links over the years. The AMSAT-NA Web Site http://www.amsat.org was
included along with others as a source of information on the amateur radio
satellites.
"Mr. Verity and I spent a few hours on the telephone talking about the
continuing magic of Amateur Radio and what AMSAT has done to spark new
ways of telecommunication over the years", said Keith. Keith is shown
operating on the satellites from his "shack" in one of the two photos
included with the story.
Keith reports that Mr. Verity was quite impressed with the ease with which
we regularly communicate through our fleet of AMSAT satellites. "He was
most impressed with the fact that we can, for example, communicate via
one of our MICROSATS using nothing more sophisticated than a low powered
hand-held radio and a flexible antenna," said Keith. "The carpenter's rule
antenna material we regularly use aboard our satellites also caught his
attention," he said.
Says Keith, "Needless to say, this story is great publicity for AMSAT and
for Amateur Radio as a whole. If it sparks enough interest in just one
youngster to become a Ham then it was well worth the effort!"
[Info via the AMSAT-NA News Service]
* MIR APRS EXPERIMENT *
The MIREX (Mir International Amateur Radio Experiment) team would like to
announce an Automatic Packet/Positioning Reporting System (APRS) test that
is scheduled for 10-Mar-98 beginning at 1455 UTC and lasting through 1651 UTC.
APRS stations will be allowed to use the Digital Repeater (R0MIR) on the
Russian Mir Packet Station during the period of this experiment, which will
cover approximately 99% of the USA on two orbits of Mir.
MIREX hopes that schools will be able to take part in the experiment by
logging into one of the APRS Web sites (www.aprs.net) to track APRS beacons
across the US. Hams are also encouraged to set up packet stations at
schools to allow students and educators to witness the experiment first-hand.
The Mir PMS frequency is currently 145.985 FM simplex. The Mir Digital
Repeater callsign is R0MIR. After 10-Mar-98 @ 1651 UTC, APRS should NOT
be used via Mir.
A recent 2-line Keplerian data set for use in tracking Mir follows:
Mir
1 16609U 86017A 98063.08565753 .00008828 00000-0 10311-3 0 3011
2 16609 51.6575 217.9855 0005337 84.5056 275.6535 15.62474297687614
[Info via Dr. Dave Larsen, N6CO]
* EVIDENCE OF ICE DISCOVERED ON MOON *
There is a high probability that water ice exists at both the north and
south poles of the Moon, according to initial scientific data returned by
NASA's Lunar Prospector. Just two months after the launch of the cylindrical
spacecraft, mission scientists have solid evidence of the existence of lunar
water ice, including estimates of its volume, location and distribution.
"We are elated at the performance of the spacecraft and its scientific
payload, as well as the resulting quality and magnitude of information
about the Moon that we already have been able to extract," said Dr. Alan
Binder, Lunar Prospector Principal Investigator from the Lunar Research
Institute, Gilroy, CA.
The presence of water ice at both lunar poles is strongly indicated by
data from the spacecraft's neutron spectrometer instrument, according to
mission scientists. Graphs of data ratios from the neutron spectrometer
"reveal distinctive 3.4 percent and 2.2 percent dips in the relevant curves
over the northern and southern polar regions, respectively," Binder said.
This is the kind of data 'signature' one would expect to find if water
ice is present."
However, the Moon's water ice is not concentrated in polar ice sheets,
mission scientists cautioned. "While the evidence of water ice is quite
strong, the water 'signal' itself is relatively weak," said Dr. William
Feldman, co-investigator and spectrometer specialist at the Department of
Energy's Los Alamos National Laboratory, NM. "Our data are consistent with
the presence of water ice in very low concentrations across a significant
number of craters." Using models based on other Lunar Prospector data,
Binder and Feldman predict that water ice is confined to the polar regions
and exists at only a 0.3 percent to 1 percent mixing ratio in combination
with the Moon's rocky soil, or regolith.
Assuming a water ice depth of about a foot and a half (0.5 meters), the
depth to which the neutron spectrometer's signal can penetrate, Binder
and Feldman estimate that the data are equivalent to an overall range of
11 million to 330 million tons (10-300 million metric tons) of lunar water
ice, depending upon the assumptions of the model used. This quantity is
dispersed over 3,600 to 18,000 square miles (10,000-50,000 square kilometers)
of water ice-bearing deposits across the northern pole, and an additional
1,800 to 7,200 square miles (5,000-20,000 square kilometers) across the
southern polar region. Furthermore, twice as much of the water ice mixture
was detected by Lunar Prospector at the Moon's north pole as at the south.
"This finding by Lunar Prospector is primarily of scientific interest at
this time, with implications for the rate and importance of cometary impacts
in the history and evolution of the Solar System," said Dr. Wesley Huntress,
NASA Associate Administrator for Space Science. "A cost-effective method to
mine the water crystals from within this large volume of soil would have to
be developed if it were to become a real resource for drinking water or as
the basic components of rocket fuel to support any future human explorers."
Lunar Prospector is scheduled to continue its current primary data gathering
mission at an altitude of 62 miles (100 kilometers) for a period of ten more
months. At that time, the spacecraft will be put into an orbit as low as six
miles (10 kilometers) so that its suite of science instruments can collect
data at much finer resolution in support of more detailed scientific studies.
In addition, surface composition and structure information developed from
data returned by the spacecraft's Gamma Ray Spectrometer instrument will be
a crucial aspect of additional analysis of the polar water ice finding over
the coming months.
[Info via NASA Press Release 98-38]
* FEEDBACK/INPUT WELCOMED *
Comments and input for SpaceNews should be directed to the editor (John,
KD2BD) via any of the paths listed below:
WWW : http://www.njin.net/~magliaco/
PACKET : KD2BD @ KS4HR.NJ.USA.NA
INTERNET : kd2bd@amsat.org, magliaco@email.njin.net
SATELLITE : AMSAT-OSCAR-16, LUSAT-OSCAR-19, KITSAT-OSCAR-25
<<=- SpaceNews: The first amateur newsletter read in space! -=>>
<<=- Serving the planet for 10 years -=>>
/EX
-=-=-=-=-=-=-=-=-=-=-=-=- John A. Magliacane, KD2BD -=-=-=-=-=-=-=-=-=-=-=-=-
Internet : kd2bd@amsat.org | Voice : +1.732.224.2948
Satellite : OSCAR-16, OSCAR-19 | Morse : -.- -.. ..--- -... -..
Packet : KD2BD @ KS4HR.NJ.USA.NA | WWW : http://www.njin.net/~magliaco/
Video : 426.250 MHz/439.250 MHz | FAX : +1.732.224.2060
-=-=-=-=-=-=-=-=- Hiroshima '45, Chernobyl '86, Windows '95 -=-=-=-=-=-=-=-=-
Hа сегодня все, пока!
=SANA=
Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: Clues To Possible Life On Europa May Lie Buried In Antarctic Ice
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Marshall Space Flight Center Press Release
Clues to possible life on Europa may lie buried in Antarctic ice
March 5, 1998: More than a century ago, science fiction pioneer Jules Verne
wrote about people swept "Off on a Comet" and into space where they lived
more or less happily ever after.
Verne's 1877 book (also published as "Hector Servadac") was a bit fanciful,
but it had an element of truth: life may have hitchhiked across the solar
system. The proof may be found at the ends of the Earth. This week, American
and Russian scientists are examining deep ice from the Antarctic and hoping
to find clues that fungi, bacteria, and even diatoms could survive
conditions in icy solar system bodies. This would help make the South Pole
one of the first destinations for the growing field of astrobiology.
"It's possible to say that ancient impacts of asteroids on the [Antarctica]
Earth could have ejected soil, rocks, and seawater containing
terrestrial microorganisms into space, and that they may have made it to
other places in the solar system," explained Richard Hoover at NASA's
Marshall Space Flight Center. Hoover is an X-ray astronomer who is also is
internationally known for his work on diatoms and a firm believer that
living microorganisms locked in ice have a chance of remaining viable for
long periods in outer space.
The debate over whether the Antarctic Allan Hills meteorites brought life
from Mars (or were contaminated by life on Earth) is the best known case.
Hoover said that other evidence abounds, including asteroids striking the
Earth or Mars and blasting materials into space, the survival of
streptococcus bacteria on the Surveyor 3 moon lander, and the survival of
microorganisms inside Antarctic ice.
The possibilities expanded this week when NASA released new images and data
that Europa, one of Jupiter's larger moons, slush and perhaps liquid water
near the surface. That raises the intriguing possibility that Europa may
harbor life.
Discoveries on the Earth over the last few years show that life thrives or
can be preserved in a range of "hostile" conditions, from volcanic vents
deep in ocean trenches, to ice more than 400,000 years old, to Siberian
permafrost more than 5 million years old.
This week, Hoover and Dr. S. S. Abyzov of Russia's Institute of Microbiology
of the Russian Academy of Sciences in Moscow are examining ancient ice
drilled at Russia's Vostok (East) Station about 1,000 km (1,600 mi) from the
South Pole. Eventually, they hope to examine water taken from inside a lake
- liquid, not ice - discovered under Vostok Station in 1996.
The first samples being examined are from 386 meters (1,266 ft) down; the
deepest in this set is from 1,249 meters (4,097 ft). Samples from as deep as
3,610 meters (11,840 ft) are on their way from Vostok to the Institute of
Microbiology. Abyzov says that portions will be brought to Marshall later
this year.
Russian scientists have been drilling at Vostok since 1974. In 1996, seismic
and other tools revealed the lake's presence in 1996. Lake Vostok is
overlaid by about 3,710 meters (12,169 ft) of ice and may be 500,000 to 1
million years old. Since the discovery, drilling has gone slowly while
procedures are worked out to keep it pristine. No one has seen or sampled
the lake - the deepest ice sample is from 100 meters (328 feet) above the
liquid surface - nor is anyone sure why it is liquid, hence the scientific
curiosity. (Check below for links to stories about Lake Vostok.)
While Lake Vostok holds clues about life on Earth, it also is a
good model for conditions on Europa (the image links to the latest
news from Europa). The lake is about 48 by 224 km (30 by 140 mi) in size -
about the size of Lake Ontario - and 484 meters (1,600 ft) deep. Recent data
indicate that it has about 50 meters (165 ft) of sediment at the bottom.
"Recent research [shows] that extremely severe conditions of cosmic
environments do not exclude the possibility that microorganisms may exist in
anabiotic states at high altitudes in interplanetary space," Abyzov wrote in
a recent paper. The only way to resolve the question is to use the Antarctic
as a model for conditions in comets, the Martian ice caps, and other icy
moons orbiting Jupiter and Saturn.
At Vostok station in 1975, Abyzov discovered bacteria, fungi, diatoms, and
other microorganisms which were blown to Antarctica by winds from lower
latitudes. The numbers of the organisms at different depths, and thus
different ages of the ice, change with major climate changes on the Earth.
Thus, the ice also serves as a time capsule, preserving specimens of life as
far back as 500,000 years. This offers the potential for studying how
genetic material changes over the centuries.
Abyzov brought his samples to Marshall to use the Environmental Scanning
Electron Microscope, or ESEM, a relatively new tool that Marshall uses to
analyze how materials fail and break. It was originally designed to analyze
biological specimens in their natural environment, without coating them in
gold to make them reflective. And that's ideal for observing whatever is in
the ice. It also uses an X-ray scan to analyze the elements in a target, an
important step in determining whether an object is organic.
The ice specimens will be analyzed at Marshall over the next week, then
Abyzov will go to the Jet Propulsion Laboratory to work with another
colleague with different analytical tools. Check back in a few days for a
follow-up story on what the ESEM finds.
Hа сегодня все, пока!
=SANA=
Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: Lunar Ice: Privat Company's Mission-In-Progress Could Lead To Sample R
Subject: Lunar Ice: Privat Company's Mission-In-Progress Could Lead To Sample R
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CONTACT: Beth Elliott
516/579-1249 Direct
eelliott@appliedspace.com
For Immediate Release
LUNAR ICE: PRIVATE COMPANY'S MISSION-IN-PROGRESS
COULD LEAD TO RETURN OF SAMPLES
Applied Space Resources, Inc.'s current engineering work for a
September 2000 Lunar Sample Return Mission will provide framework for
polar exploration
Bethpage, NY - 03/06/98 - As NASA announced the Lunar Prospector's
discovery of polar ice on the Moon, Applied Space Resources, Inc.
(ASR) of Long Island, New York said the robotic sample return mission
it is currently engineering will provide a proof of concept for
low-cost commercial lunar sample retrieval missions. ASR's lunar
sample return mission, the Lunar Retriever, will retrieve lunar rock
and soil to sell both to research organizations and, through
commercial channels, to the general public. ASR expects to launch
Lunar Retriever by September 2000, the 30th anniversary of Luna 16,
the first robotic sample return mission to soft land on the moon.
"Based on the spacecraft designed for the Lunar Retriever mission, a
follow-on mission to retrieve lunar soil and ice samples could be
launched within six to twelve months after the initial mission at a
cost well under $100 million," says Denise Norris, ASR's CEO.
When passed, the Commercial Space Act of 1997 will specifically
instruct NASA to look to private companies like ASR to develop the In
Situ Resource Utilization (ISRU) technology critical to its plans for
future space exploration and colonization. And technology for using
the newly-discovered lunar ice would give space exploration an
immense boost. Water is critical to human life support, and can also
be separated into its chemical components of hydrogen and oxygen:
oxygen for breathing, and combinations of hydrogen and oxygen for
rocket fuel. But the cost of lifting the thousands of gallons of
water into low Earth orbit alone, much less transporting it from
there to the Moon, would be prohibitive.
The Lunar Prospector data suggests there is an immense amount of
water on the Moon in the form of ice mixed in with lunar soil. But
before space explorers can make use of the water, scientists and
engineers will have to figure out how best to extract it from the
lunar soil, in which it is sparsely scattered. The Lunar
Prospector's investigators, Dr. Alan Binder of the Lunar Research
Institute in Gilroy, California and Dr. William Feldman of the Los
Alamos National Laboratory in New Mexico, say the data suggests that
water ice is confined to the polar regions and exists at only a 0.3
percent to 1 percent mixing ratio in combination with the rocky lunar
soil.
Jay Manifold, ASR's Vice President of Research and Development, says,
"The key to ISRU development, including research on how to extract
and use lunar ice, is putting samples of lunar resources in the hands
of scientists on Earth. ASR's goal is to use existing technologies
to deliver spacecraft to any destination with precision, and return
resources and information with equal precision, for a profit. Our
Lunar Retriever, for example, will use the same Lockheed-Martin
Athena 2 rocket as the Lunar Prospector. A mission to collect
samples of lunar polar ice, and return them in cryogenic storage,
would be a logical next step for us."
ASR's principals stress the importance of entrepreneurs to opening
near-Earth space to the resource development that will make possible
fulfilling NASA's exploration goals. ASR will make its services
available to private and public concerns alike, but will take no
subsidies. "Humankind will only benefit from the resources of space
when they are developed by private enterprises such as ours," says
Denise Norris. "We intend to use our knowledge, creativity, hard
work and business vision to demonstrate the viability of
market-driven space missions. We will not go to the public asking
them to send us into space. We will go into space first, then come
to the public with something to offer: the productive utilization of
the vast resources of near-Earth space."
More information about Applied Space Resources and its Lunar
Retriever mission can be found at the ASR web site,
http://www.appliedspace.com.
# # #
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=SANA=
Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: New Model Explains Venusian Land Forms
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Washington University in St. Louis
New Model Explains Venusian Land Forms
March 5, 1998
Because Earth and Venus have nearly the same size, scientists long
have called them planetary twins.
But scientists theorize the processes that form the geological
features of the planets are different. Earth forms its continents and
physical features and sheds its interior heat by plate tectonics.
Though Venus might be expected to do the same, its surface shows scant
evidence for plate tectonics, and planetary researchers long have
debated, often heatedly, just what the corresponding process is on our
sister planet.
Now a new model of Venus, derived largely from the highly successful
Magellan Mission early in this decade, shows that two of the planet's
most predominant features, crustal plateaus and volcanic rises, were
formed by a mechanism similar to hot spot plumes, a process still
active on Earth today and evident in the Hawaiian Islands. Hotspots are
thermal plumes of hot rock originating deep within the Earth and
rising buoyantly upward over millions of years. They eventually surface
in dramatic, lava-spewing displays geologists call flood basalts.
The new interpretation comes from the mapping of very subtle geological
faults on the surfaces of the crustal plateaus, and was published
March 6, 1998, in Science magazine.
Roger J. Phillips, Ph.D., professor of earth and planetary sciences at
Washington University in St. Louis, and his colleague Vicki L. Hansen,
Ph.D., professor of geological sciences at Southern Methodist University
in Dallas, analyzed recent data and hypothesize that a thickening of
the Venusian lithosphere, the outer strong shell of a rocky planet,
approximately one billion years ago largely shut down the creation of
crustal plateaus and led to the formation of volcanic rises instead.
Phillips and Hansen suggest that the thickening occurred rapidly in
geological time, in 100 to 200 million years. The thickening prevented
the plumes from melting substantially and creating new crustal material
to form crustal plateaus. Volcanic rises form when there is
not massive melting in the plumes.
Phillips and Hansen estimate the Venusian lithosphere is about 60
miles thick today, compared with about 24 miles thick at the end of
the 'thin lid' era, which they suggest lasted up until about one
billion years ago.
"To maintain the thin lithosphere you have to have some sort of
recycling going on, which on Earth is plate tectonics, but that's not
the case with Venus over the past billion years," said Phillips. "Our
calculations also show that you get plenty of plains volcanism during
the thin lid era, almost an embarrassment of riches, with formation
going on almost constantly up to the point where the lithosphere
thickens.."
That conclusion clashes with another popular planetary theory that
holds that plains formation was an abrupt episode on Venus.
Phillips said the lack of water on Venus no doubt contributed to the
formation of the thickened lithosphere.
"The rocks are stronger on Venus probably because of a lack of water,"
he said. " It probably got to the point where the stresses induced by
the interior just couldn't break the strong rocks, and the process of
lithospheric recycling, which maintained the thin lid, just quit.
"Water is the basic difference between Venus and Earth in this context
Water makes the lithosphere of Earth relatively weak, and lack of water
makes this structure relatively strong on Venus. Whether you have
recycling of the lithosphere into the mantle comes down to a competition
between how strong the lithosphere is and how much force from
the convecting mantle can be applied to break the lithosphere. This
competition basically operates differently on the two planets."
Because the Phillips and Hansen model indicates a recycling process
during the thin lid era, it's conceivable that Venus was using plate
tectonics during its geological heyday.
"Prior to the thickening of the lithosphere, Venus could have had
plate tectonics, as far as we're concerned," Phillips said. "There was
some kind of lithospheric recycling. It may have been plate tectonics
or something else, but it was there."
The model also couples the climate and interior evolution of Venus,
the planet that suffers from the runaway greenhouse effect to give a
present-day surface temperature of nearly 900 degrees Fahrenheit. All
of the volcanism that went on during the early years of the
planet pumped so-called greenhouse gases sulfur dioxide and carbon
dioxide in the Venusian atmosphere, so that the surface temperature
was even hotter then.
"The gases increased the greenhouse effect, which in turn raised
surface temperatures, and that in turn led to more interior melting,
which resulted in more greenhouse gases being released," Phillips said.
"There is a very tight coupling between climate evolution
and interior evolution on Venus over much of its history, and that is
something we're just beginning to take seriously on Earth.
###
Contact: Tony Fitzpatrick
p72245tf@wuvmd.wustl.edu
(314) 935-5272
Washington University in St. Louis
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Дата: 10 марта 1998 (1998-03-10)
От: Alexander Bondugin
Тема: Mars Surveyor 98 Update - March 6, 1998
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Mars Surveyor 98 Project Status Report
March 6, 1998
John McNamee
Mars Surveyor 98 Project Manager
Orbiter and lander integration and test activities are proceeding on
schedule with no significant problems. Orbiter electromagnetic
compatibility testing is in process and will be completed next week.
Mechanical integration of the lander to the cruise configuration is in
process. The lander vehicle will be encapsulated within the aeroshell on
Mar 9. The lander spacecraft in full cruise configuration will be
transported to the acoustics lab at Lockheed Martin on Mar 18.
The Thermal and Evolved Gas Analyzer (TEGA) flight instrument integration
is complete. Testing and calibration of the TEGA is in process at the
University of Arizona.
For more information on the Mars Surveyor 98 mission, please visit this
website:
http://mars.jpl.nasa.gov/msp98/
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