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发信人: bage (网事如疯·春心萌动), 信区: AerospaceScience
标 题: SpaceViews -- 2000 September 25(转载)
发信站: 哈工大紫丁香 (2000年12月23日17:14:57 星期六), 转信
【 以下文字转载自 bage 的信箱 】
【 原文由 hitsma@0451.com 所发表 】
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S P A C E V I E W S
Issue 2000.39
2000 September 25
http://www.spaceviews.com/2000/0925/
*** News ***
STS-106 Mission Ends with Florida Landing
Scientists Ask NASA and Congress to Resume Pluto Mission
NASA: Costs of Science Missions Growing
British Report Recommends Investment in Asteroid Search
Titan 2 Launches Weather Satellite
Japan Writes Off Orbiting X-Ray Observatory
NEAR Reveals Eros to Be Ancient, Rock-Strewn Asteroid
Unity Backup Selected to Become Station Propulsion Module
Gore Calls for "Renewed" Space Program
SpaceViews Event Horizon
Other News
*** Articles ***
The Rise and Fall of Martian Life
*** News ***
STS-106 Mission Ends with Florida Landing
The space shuttle Atlantis landed safety at the Kennedy Space
Center in Florida, bringing to an end a mission to prepare the
International Space Station for its first long-term crew.
The shuttle touched down on schedule at the Kennedy Space
Center, Florida, at 3:56 am EDT, 11 days, 19 hours, and 10 minutes
after launching from the space center. The landing, the 23rd
consecutive landing of the shuttle at KSC, took place with no problems
reported.
The landing ended mission STS-106, a successful trip to the
International Space Station. Its seven-man crew hauled 3,000
kilograms (6,600 lbs.) of supplies and equipment into the station from
both the shuttle and an unmanned Progress spacecraft that docked to
the station's new Zvezda module in August. The crew put everything
from food and water to the station's toilet and exercise treadmill in
place for Expedition One, the station's first long-term crew,
scheduled to arrive at the station in early November.
The crew also installed three batteries in Zvezda and replaced
two more in Zarya. However, one of the three batteries installed in
Zvezda failed to work, despite troubleshooting efforts by the shuttle
crew. Since the battery is not critical -- Zvezda can function
normally with as few as five batteries working -- work to repair the
battery will be left to the Expedition One crew.
Outside the station, astronaut Ed Lu and cosmonaut Yuri
Malenchenko performed a six-hour, 14-minute spacewalk early September
11. The two installed a magnetometer on Zvezda that will be used to
provide attitude control information and also attached several data,
power, and communications cables linking Zarya and Zvezda.
The shuttle also performed four reboost maneuvers during the
week it was docked to the station, raising its orbit by an average of
22.5 km (14 mi.) to 388 by 375 km (240 by 232 mi.)
In a change of pace from the recent past, when months passed
between shuttle missions, work is already in progress for the next
shuttle mission, STS-92. The shuttle Discovery is already on the pad
for its launch, currently scheduled for October 5. A seven-person
crew will revisit ISS and install the "Z1 truss", the base for what
will eventually become an extensive truss structure that will hold
most of the station's solar panels. The crew will also install a new
docking port on the Unity module that will be used by future shuttle
missions.
Scientists Ask NASA and Congress to Resume Pluto Mission
Fearing that an opportunity to study Pluto's tenuous
atmosphere might be lost for centuries, scientists this week expressed
their concern over NASA's plans to delay a spacecraft mission to the
distant planet.
The Division for Planetary Sciences (DPS) of the American
Astronomical Society issued a statement Thursday expressing its
concern over a directive issued by NASA earlier this month that
stopped work on the Pluto-Kuiper Express (PKE) mission.
NASA associate administrator Ed Weiler told Congress last week
that he issued the stop-work order because the cost of PKE and a
related mission, Europa Orbiter, has doubled from a 1998 estimate of
$700 million, largely because of launch vehicle costs and technologies
needed for the two missions.
Weiler said he stopped work on PKE so that NASA could focus on
Europa Orbiter, a mission he said was a higher priority that the Pluto
probe. "Basically, I directed the project to go full speed on Europa
to give us the earliest possible launch of that mission," Weiler told
a House of Representatives subcommittee September 13.
That decision did not sit well with the DPS, whose 1,225
members make up the world's largest professional organization devoted
to planetary science. The DPS said that astronomers have expressed
"major concerns" over the decision to halt work on PKE.
The DPS "has urged that NASA and the US Congress to find a way
to fund this important mission, but not at the expense of other
equally important planetary missions or its basic research and
analysis programs," it noted in a statement.
The concerns about the mission focus largely on its time-
sensitive nature. PKE was to launch in 2004 and use a gravity-assist
flyby of Jupiter to arrive at Pluto around 2012. If the launch is
delayed much beyond 2004, the window for the Jupiter gravity-assist
will close, delaying the spacecraft's arrival at Pluto by as much as
seven years.
Moreover, Pluto goes around the Sun in an elliptical orbit,
and passed through perihelion, the closest point in its orbit to the
Sun, a decade ago. As Pluto moves away from the Sun it will cool, and
its tenuous atmosphere -- with a surface pressure just a few
millionths that of the Earth -- will begin to freeze out. That
atmosphere is expected to freeze out completely within the next two
decades, depriving scientists of a chance to study it for more than
two centuries.
Weiler said he was aware of the unique constraints for a Pluto
mission when he made the decision to stop work on PKE. "Certainly
after 2006, I believe, we miss the deadline [for a Jupiter flyby] and
miss the opportunity for many, many years down the road," he said.
"But all that taken into consideration, I still believe that Europa is
a higher priority mission."
The DPS leadership believes that work on PKE must resume by
the end of the year to avoid missing a 2004 launch date. To that end,
the organization is talking with NASA and Congress about the mission,
according to DPS chairman Robert Nelson, an astronomer at JPL.
"The DPS has an ongoing dialogue with NASA, its advisory
committees, and with Congress and there is nothing to prevent this
issue from being discussed," he said. Further action, he noted, "is
still under discussion."
Nelson also said that the DPS was open to working with other
organizations, such as The Planetary Society, about PKE. The society
called on its 100,000 members last week to write members of Congress,
urging them to restore funding for the mission.
"A modest increase in the NASA budget -- say two percent --
would solve the funding problem for the Outer Planets program," said
Lou Friedman, executive director of The Planetary Society.
Alan Stern, director of the Department of Space Studies at the
Boulder, Colorado office of the Southwest Research Institute and a
longtime proponent of a Pluto mission, said that while he was "very
surprised" at the stop-work order, he was optimistic that funding for
the mission would resume soon.
"The exploration of Pluto-Charon and the Kuiper Belt is both
scientifically and publicly appealing, and popular," he said. As for
getting a mission to Pluto before its atmosphere freezes out, he
concluded that "if we can launch by 2004 or perhaps 2006, we're in
good shape. Otherwise, my feeling is that all bets are off."
NASA: Costs of Science Missions Growing
The costs of many of NASA's future space science missions have
grown considerably over the last two years, a situation that may lead
to the delay, but not cancellation, of some projects, a NASA official
said last week.
Speaking before the space committee of the House Science
Committee, Ed Weiler, NASA associate administrator for space science,
said that most programs are now asking for larger but more realistic
budgets that could stretch the agency's resources in future years.
The remarks by Weiler were overshadowed by news that NASA
headquarters had issues a "stop work order" on the Pluto/Kuiper
Express (PKE) mission, a move that puts the planned flyby of Pluto on
indefinite hold and may effectively cancel the mission in its present
form.
Weiler said work on the Pluto mission was suspended because
the costs for it and Europa Orbiter, another mission that will use
many of the same technologies and subsystems as PKE, had doubled since
a 1998 estimate of $700 million for both.
The Pluto and Europa missions are not alone in seeing their
budgets grow. "Most of the projects I was given two years ago are now
coming in with much bigger budgets," Weiler said. He added that the
increased budgets are actually a welcome thing, since they reflect a
more realistic assessment of the cost of the missions.
"That's good news, in a way, because I believe these are more
reasonable budgets," he said. "The engineering optimism has been
taken over by engineering reality."
Although growing budgets led to the effective cancellation of
the Pluto mission, Weiler said he does not believe that other missions
will meet a similar fate in the near future.
"I don't anticipate at this point in time stopping work on any
other project in the near future," he said. "Many of the projects are
so important that we will let them slip."
One solution to the growing budget costs is to spend more
money in the early phases of a mission, when the technology is being
developed. This allows engineers to determine what technologies
critical for the mission require more work before beginning work
building the spacecraft itself, saving money down the road in the more
expensive phases of a mission's development.
Weiler gave as an example the Space Interferometry Mission
(SIM), a mission that would combine the light from several telescopes
in space to create a single high-resolution image. When first
proposed by NASA in the mid-1990s, the agency planned to start work on
the spacecraft itself in 2001 and launch it in 2005. However, the
agency now plans to wait until 2005 to start work on the mission, a
move that may be delayed even further.
"It's now looking like the technology is going to be tougher,"
he explained. "They're going to spend more time on technology, and
they're not going to get a new start until the technology is ready."
If necessary, though, the agency will cancel missions,
according to Weiler. He pointed to Space Technology 4, also known as
Champollion, a New Millennium Program mission that was cancelled by
NASA in June 1999. Weiler said the cost of the mission has grown to
$250 million, compared to the $100 million for a typical New
Millennium mission.
Weiler also defended NASA's decision to end the mission of the
Extreme Ultraviolet Explorer (EUVE), a spacecraft launched in 1992
that has been in an extended mission since 1996. Weiler noted that a
senior review of EUVE earlier this year by outside scientists -- not
NASA -- recommended that EUVE's mission be terminated.
"It's not a money issue, it's based on the science," Weiler
said. He said that if Congress gave him an addition half a million to
a million dollars, the cost to continue EUVE an additional year, "I
would rather take that money and put it into Chandra, Mars Global
Surveyor, or the Hubble Space Telescope, because I believe the
[scientific] community would tell us the money would be better spent."
Overall, Weiler believes that, despite the growing costs of
missions, NASA's space science programs are still in good shape. "We
will not have a program as aggressive next year as we thought two
years ago," he noted. "But it will be doable."
British Report Recommends Investment in Asteroid Search
A report released Monday recommends that the British
government make a multi-million dollar investment in search programs
and other efforts to deal with the threat posed by near-Earth
asteroids and comets.
The "Report of the Task Force of Potentially Hazardous Near
Earth Objects", released Monday, concluded that the United Kingdom can
and should play a major role in the search for objects that could
collide with the Earth.
"The threat from Near Earth Objects raises major issues," the
report, drafted by a committee of three scientists appointed by the
government earlier this year, concluded. "The United Kingdom is well
placed to make a significant contribution to what should be a global
effort."
The task force recommended in the report that the UK become
more involved in programs to detect and monitor NEOs. Its leading
recommendation was that the country work with others in Europe to
build a 3-meter (118-inch) telescope in the southern hemisphere that
would be dedicated to searching for NEOs. Such a facility would fill
a gap in current search efforts, which are mostly based in the
northern hemisphere, and would be able to detect smaller objects that
current telescopes.
"We have considered the possibility of using older existing
telescopes for the systematic survey and discovery of these objects,
but have generally rejected the idea because adapting such equipment
would be expensive and the resulting telescopes would not be
competitive for long," the report noted. "Only a new dedicated would
make a satisfactory contribution to the world effort."
The report did recommend that other ground- and space-based
telescopes in use or under development also be drafted into the effort
to both search for new NEOs and track existing ones. In most cases,
these facilities, such as ESA's proposed GAIA astrometry mission,
would perform NEO work in addition to other tasks.
The task force also recommended that the UK support other
research to better understand the composition and nature of NEOs,
through ground-based telescopes and small spacecraft missions, and
fund studies to look into the consequences of a NEO impact with the
Earth and ways to deflect and incoming object.
In addition to suggesting that international and European
organizations be created to coordinate and share information about NEO
work, the task force concluded the UK should set up its own
organization for NEO work. The British Center for Near Earth Objects
would coordinate national NEO work and also provide information to the
public "should the need arise."
The cost of the entire program was not included in the report,
although the task force admitted that some of its recommendations,
such as a 3-meter telescope, would be "expensive." Outside experts
have estimated that such a program would cost the British government
up to as much as 10 million pounds (US$14 million) a year. By
comparison the US, the leading nation in current search efforts,
spends only a few million dollars a year.
Lord Sainsbury, the British science minister, thanked the task
force for the report but was noncommittal on how the government would
act upon those recommendations.
"I welcome the Task Force's approach, which includes proposals
for collaboration with international partners," he said in a statement
Monday. "Over the next couple of months I will be considering the
Government's response to the Task Force's recommendations in
consultation with colleagues".
The report was widely applauded by scientists both in the UK
and around the world involved with NEO work. Duncan Steel, a British
astronomer involved with NEO studies, called the report's
recommendations "suitably ambitious."
"They are ambitious in that they would place the UK as the
number two nation globally in such activity," he explained, adding
that if the UK did build a 3-meter telescope "then the current US NEO
search activity would be outstripped. That would, one would imagine,
provoke a response from the far side of the Atlantic."
"These recommended actions would significantly extend the
current efforts to discover and track the thousands of potentially
hazardous objects in near-Earth space," said Don Yeomans, manager of
NASA's Near-Earth Object program office. "This comprehensive report
will remain a classic in the field and it should go a long way toward
educating the public on the only type of natural disaster that could
be averted with current technology."
Spaceguard UK, a British organization that supports expanded
NEOs searches, welcomed the report but cautioned that the government
must back the report's language with action. "Spaceguard UK applauds
the [science] minister, Lord Sainsbury, on his timely decision to
investigate the most serious natural hazard facing Great Britain," the
organization said in a statement. "However, he is no doubt well aware
that actions speak louder than words, so the national and
international membership of Spaceguard UK will await the government's
plan of action with great interest."
"The hazard has now been validated," the organization
concluded, "and hopefully we will soon have the tools to reduce the
risk to manageable levels."
Titan 2 Launches Weather Satellite
A Titan 2 rocket successfully launched a polar-orbiting
weather satellite early Thursday after a one-day delay.
The converted ICBM lifted off from Space Launch Center 4 West
at Vandenberg Air Force Base, California at 6:22 am EDT (1022 UT).
Its payload, the NOAA-L weather satellite, separated from the booster
six minutes and 40 seconds after launch.
The launch was scheduled to take place Wednesday, but was
delayed when controllers discovered an overloaded set of transistors
in the booster during the countdown. Although the transistors were
not apparently damaged by the overload, controllers scrubbed the
Wednesday launch attempt until the problem was fully understood.
Operated by the National Oceanic and Atmospheric
Administration (NOAA), the NOAA-L satellite will be the second in a
series of five Polar Operational Environmental Satellites (POES) that
will operate over the next 12 years. The first, NOAA-15, was launched
in 1998; NOAA-L will be renamed NOAA-16 once it has been checked out.
Operating from a Sun-synchronous orbit 870 kilometers (540
miles) above the Earth, NOAA-L and the other POES spacecraft will be
used to provide global weather data for use on short- and long-term
forecasts and climate models. The satellite also features a COSPAS-
SARSAT transponder for use by international search and rescue efforts.
The launch is the first for the Titan 2, a refurbished ICBM,
since the December 1999 launch of a military weather satellite, also
from Vandenberg. Another Titan 2 launch, also of a military weather
satellite, is tentatively planned for January 2001 from Vandenberg.
Japan Writes Off Orbiting X-Ray Observatory
Japanese space agency officials said Wednesday they had all
but given up efforts to recover an orbiting x-ray observatory that
went into a safe mode in July indirectly caused by strong solar
storms.
Officials with the Institute of Space and Astronautical
Science (ISAS) reported September 20 that efforts to restore control
of the Advanced Satellite for Cosmology and Astrophysics (ASCA)
spacecraft had failed, and that it was unlikely control of the
spacecraft would be restored before the spacecraft reenters the
Earth's atmosphere next year.
"We regret that we must announce that the possibility that
ASCA will return to observation mode is very small, almost hopeless,"
ISAS officials H. Inoue and F. Nagase said in a statement posted on
the ASCA web site at NASA's Goddard Space Flight Center.
Problems for ASCA started on July 15 when the spacecraft
encountered strong atmospheric drag created by a solar storm that
"puffed out" the tenuous upper atmosphere. This additional drag
created a torque on the spacecraft that its attitude control system
could not compensate for, putting the spacecraft into a spin with a
period of about three minutes.
While spacecraft controllers put the spacecraft into a
protective safe mode, the torque was strong enough that it moved the
spacecraft's solar panels out of proper alignment with the sun,
reducing ASCA's ability to generate power and draining its batteries.
Efforts to restore power and charge up the batteries since
ASCA went into safe mode, but without success. "We suspect that the
battery cells may have suffered serious unrecoverable damage," Inoue
and Nagase noted.
ISAS will continue to monitor the spacecraft as its orbit
decays, and the agency expects the spacecraft will reenter and burn up
in the Earth's atmosphere next year.
ASCA, originally named ASTRO-D, was launched by ISAS in
February 1993. The 417-kg (917-lb.) spacecraft features an x-ray
telescope and a pair of cameras to record images from the telescope.
The spacecraft was designed to perform studies ranging from searches
for black holes to studies of dark matter and the chemical evolution
of the universe.
While primarily an ISAS mission, there has been considerable
American cooperation with ASCA. The spacecraft's telescope was
fabricated by NASA's Goddard Space Flight Center, in cooperation with
Nagoya University in Japan. MIT and Penn State also worked with ISAS
and Osaka University to develop the CCD camera on the spacecraft.
Although less capable than newer x-ray observatories, like
Chandra an XMM-Newton, ASCA allowed astronomers to perform long-term
observations of objects that are not possible with the larger
telescopes, given the greater demand for their use.
"ASCA lived twice as long as the planned mission life, and we
believe that the successful collaboration between Japanese and US
scientists has produced tremendous fruitful scientific results from
ASCA," Inoue and Nagase said.
ISAS had planned to replace ASCA with a new x-ray observatory,
ASTRO-E, in February. However, ASTRO-E failed to reach orbit when a
malfunction with its M-V booster kept the satellite from reaching
orbital velocity.
NEAR Reveals Eros to Be Ancient, Rock-Strewn Asteroid
Scientists analyzing data from NASA's NEAR Shoemaker
spacecraft have concluded that the near-Earth asteroid Eros is a body
that dates back to the formation of the solar system and it littered
with a surprising amount of rocky debris.
A special section of several papers published in the September
22 issue of the journal Science summarize planetary scientists'
current state of understanding of the small asteroid, a body that may
be similar to thousands of other small bodies in the solar system.
"It looks like Eros is one of the most ancient rocks in the
solar system, according to the initial data from NEAR," said Jacob
Trombka, a scientist at NASA's Goddard Space Flight Center and also
leader of the science team for NEAR's X-ray Gamma-Ray Spectrometer
(XGRS).
Data from the XGRS on the elemental composition of Eros'
surface show that the asteroid appears to be undifferentiated; that
is, the surface has a mixture of both light and heavy elements, like
chondrite meteorites that have reached the Earth. This leads
scientists to believe Eros is made of materials left over from the
formation of the solar system and has not been subjected to heating
that would process the asteroid, separating light elements from
heavier ones.
The results published in Science are similar to those first
released to the public in May at a meeting of the American Geophysical
Union in Washington.
"We can now say that Eros is an undifferentiated asteroid with
homogeneous structure, that never separated into a distinct crust,
mantle and core," said Andrew Cheng, NEAR project scientist at the
Applied Physics Lab, part of the Johns Hopkins University.
Trombka cautioned that XGRS can only measure the composition
of the asteroid's surface, not its interior, so that micrometeorite
impacts or cosmic rays could have altered the composition of surface
layer compared to Eros' interior.
"However, we made the same x-ray measurements of the Moon
during the Apollo missions," explained Trombka. "The Apollo astronauts
took core samples, and the composition of the samples agreed with our
surface map. This gives us confidence that our surface map of Eros
reflects its true composition." In addition, the XGRS will be able to
probe more than ten centimeters (four inches) below the surface later
in the mission when NEAR comes closer to the asteroid.
A separate paper in Science provided a measurement of the mass
and density of Eros. That work concluded the asteroid has a mass of
6.7 million billion kilograms (14.7 million billion pounds) with a
density of about 2.7 grams per cubic centimeter, a value similar to
the density of the Earth's crust.
That density is consistent with the asteroid being a
consolidated body rather than a loose agglomeration of small bodies,
also known as a "rubble pile". The asteroid's irregular shape is also
evidence that Eros is a solid, if heavily fractured body: a rubble
pile as large as Eros would not be able to maintain such an irregular
shape for long before self-gravity began to smooth out some of the
features, scientists noted.
While planetary scientists believe that have a good
understanding of the asteroid's internal structure and composition,
they are puzzled by images of the surface that show a large amount of
rocky debris, apparently left over from asteroid impacts, on Eros'
surface.
The amount of debris on the surface is puzzling, said Joseph
Veverka of Cornell University, because the asteroid's very small
escape velocity -- as little as 3.1 meters per second (6.9 mph) --
should allow most of the debris created by an impact to escape from
the asteroid altogether. "Intuition and calculation tell you that
most of the debris produced in a collision would have escaped -- but
the surface is full of it," he noted.
"What is striking about Eros," he added, "is that if I look at
the Moon in great detail, I see lots of tiny craters and fewer blocks
of rock. But on this object, when I get down to sizes the size of a
car, there are very few craters and lots of boulders."
There are a couple possible, but poorly-understood,
explanations for the large amount of debris. "One is that we simply
don't understand cratering events on small objects, and somehow the
debris gets thrown out at very low speeds," explained Veverka. "Or the
ejected material ends up in the same orbit as Eros, and over time the
asteroid runs back into its own debris and gathers it up, which is
equally bizarre. We simply don't understand this."
Veverka and other scientists will get more opportunities to
try to understand Eros as the spacecraft and most of its instruments
-- with the exception of a near-infrared spectrometer which failed in
June -- continue to return data.
Currently in a circular 100-kilometer (62-mile) orbit around
Eros, NEAR Shoemaker will sweep lower in October, passing just six
kilometers (3.7 miles) from the surface on October 25. The
spacecraft's mission is slated to end in February of next year with a
controlled descent to the asteroid's surface.
Unity Backup Selected to Become Station Propulsion Module
NASA has selected a design based on the Unity docking node to
be the new Propulsion Module for the International Space Station,
officials said this week.
Space station managers said that the so-called "Node X", based
on a structural test article built during the assembly of the Unity
module, will be used starting later this decade to help reboost the
station and maneuver it around any orbital debris.
The design was selected after NASA earlier this year stopped
work on a custom-built propulsion module being developed by Boeing.
NASA halted work on the module in May when it appeared the module
would cost up to $200 million more than the $540 million allocated for
it.
Because Node X will use an already-built structural test
article the module will look nearly identical to the Unity module
already in orbit. Guidance and navigation systems will be added to
the node to permit it to be used for station control. Little else
will be added to the module in terms of electrical systems or life
support, only the minimum needed for a safe environment within the
module.
Attached to the exterior of the module will be a self-
contained propulsion unit, housing both the set of thrusters as well
as their hydrazine propellant. Node X will be able to host up to two
such elements, although initially NASA only plans to add a single
propulsion unit. The units, not designed to be refueled while in
orbit, will be swapped out on a regular basis during shuttle missions.
Node X is scheduled for launch in mid- to late-2004 on a
shuttle mission and attached to Node 2, a docking node being built by
Italy. The module will be built by Boeing under a change to NASA's
existing contract with the company for the Propulsion Module.
Node X was selected over several competing designs studied
within NASA during the summer, including one that would have mounted
the propulsion unit on the Z1 truss element that will be added to the
station during the STS-92 shuttle mission next month.
A study by a NASA working group, the Alternate Propulsion
Module Assessment Team (APMAT), concluded in July that the Z1 module,
and not Node X, was the best option for a propulsion module. While
the group concluded that the Z1 option would have the lowest
development cost, it also noted the Z1 module had the highest
integration risk. The space agency opted instead for Node X, APMAT's
runner-up option.
NASA hopes that the Propulsion Module, with a single
propulsion element, will be able to provide half of the station's
reboost and maneuvering ability. It will supplement Progress cargo
spacecraft from Russia, as well as the space shuttle and unmanned
European and Japanese spacecraft.
The Propulsion Module was originally designed in the event
that Russia's Zvezda module would be indefinitely delayed, depriving
the station of critical maneuvering and reboost capability during the
assembly process. In addition, the Interim Control Module, another
module built in the event of Zvezda delays, will remain on the ground
in the event it is needed in the future now that Zvezda is in orbit.
Much of the demand for the Propulsion Module will come later
in the decade, as the completed space station encounters increased
atmospheric drag as the Sun's 11-year activity cycle approaches
another maximum, heating up and expanding the tenuous upper reaches of
the Earth's atmosphere.
Gore Calls for "Renewed" Space Program
Vice President Al Gore, the Democratic Party candidate for
President, says he supports a "renewed American space program",
although the details of his proposal suggest something that differs
little from current plans.
In a statement on algore2000.com, Gore's official campaign web
site, and only recently uncovered by SpaceViews, Gore outlines a plan
that would largely continue what NASA has been planning to do over the
last several years, including completing the International Space
Station and continuing the robotic exploration of Mars.
"The 20th Century will forever be remembered as the time when
we put a man on the moon," Gore is quoted as saying in the online
statement. "Together, we must work to ensure that the 21st Century is
the time when we reach even further into our solar system, and beyond
it; a time when we reap profound new insights into our own world -
from the first light that illuminated the universe, to the forces
affecting our global environment in the present day."
Gore's "bold vision for America's space program", according to
the campaign's web site, calls for a number of projects that are
already underway or are in the planning stages today, including the
completion of ISS, more robotic mission to Mars, missions to Europa to
search for potential life that may exist beneath its icy surface, and
efforts to look for Earthlike extrasolar planets.
Gore, an ardent environmentalist, also calls for continued
monitoring of the Earth from space. He also said he would support
"innovative programs connecting classrooms and students through the
Internet with experiments aboard the International Space Station and
scientific missions to the planets."
One key distinction of Gore's proposal over the current
program is a pledge to reexamine current export controls that many
aerospace companies claim have made it difficult to do business with
foreign customers, even in those countries closely allied with the
United States.
"As Joe Lieberman has advocated, after taking office,
President Gore will appoint a Presidential Commission to study the
future of the United States aerospace industry in the global economy,
reexamining export policies to permit access to global markets while
protecting national security," the statement noted. Lieberman, a
senator from Connecticut, is the Democrats' vice-presidential
candidate.
The campaign tried to describe Gore as a leader in space
policy today. "As a Senator and Vice President, Al Gore has been a
strong voice for leadership and direction in America's space program,"
the statement claimed. "Al Gore has played a leading role in defining
a new direction for the United States in space, ensuring that America
moves into the 21st century with a strong, stable, and balanced
national space program."
Gore and the Democratic Party were criticized last month by
failing to include any discussion of NASA or space in the party's
platform, the document that outline's the party's policies on a wide
range of issues.
Space was mentioned in the Republican Party's platform, saying
that the party would "continue the exploration of Mars and the rest of
the solar system." The platform also said Republicans would "restore
the integrity of the nation's space program by imposing sound
management and strong oversight on NASA."
Neither Republican Presidential candidate George W. Bush nor
the party has expanded on the language in the party platform. A lack
of discussion about NASA and space policy by either party is not
surprising, since NASA takes up only a small fraction of the overall
budget and is not generally considered a partisan issue, pitting one
party against another.
Space activists, however, plan to continue their efforts to
raise the candidates' and public's awareness of space policy in the
weeks leading up to the November 7 general election. The New England
chapter of the Mars Society is planning to hold a "Rally for Mars
Exploration" October 3 at the University of Massachusetts at Boston,
site of the first of three Presidential debates.
SpaceViews Event Horizon
Note: You can now add these events to your Palm handheld by clicking
on, or copying and pasting into a Web browswer, the URL below each
event. Visit Coola's Web site at http://www.coola.com/ for more
information about this free service.
September 25 Zenit 2 launch of a classified Russian military
satellite, from Baikonur, Kazakhstan
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969270585&type=D
September 27 Dnepr launch of five microsatellites from Baikonur,
Kazakhstan, at approximately 6 am EDT (1000 UT).
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969270478&type=D
October 1 Proton launch of the GE-1 communications satellite
from Baikonur, Kazakhstan, at 5:54 pm EDT (2154 UT).
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969879489&type=D
October 3 Rally for Mars Exploration, Univ. of Massachusetts
Boston
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969882294&type=D
October 4-10 World Space Week 2000
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969880188&type=D
October 5 Launch of the shuttle Discovery on mission STS-92 from
the Kennedy Space Center, Florida, at 9:39 pm EDT
(0139 UT Oct. 6)
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969879626&type=D
October 6 Pegasus XL launch of NASA's High Energy Transient
Explorer 2 (HETE-2) spacecraft from an L-1011
aircraft based out of Kwajalein Missile Range in the
Pacific Ocean at 1:35 am EDT (0535 UT).
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969879878&type=D
October 6 Ariane 4 launch of the Japanese N-SAT-110
communications satellite, from Kourou, French Guiana
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969880023&type=D
October 19-22 Space Frontier Conference 9, Manhattan Beach,
California
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=968079287&type=D
October 20-22 Mars Week 2000, MIT, Cambridge, Massachusetts
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969270315&type=D
October 23-27 32nd Annual American Astronomical Society Division for
Planetary Sciences Meeting, Pasadena, California
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=968079363&type=D
Other News
Republicans Attack Space Station Policy: The decision to include
Russians in the International Space Station (ISS) project was a
"debacle", according to a report released by Congressional Republicans
last week. A portion of the report "Russia's Road to Corruption",
released by the all-Republican Speaker's Advisory Group last week,
criticized the Clinton Administration for including Russia in the
project and claiming that its participation would lower costs and
hasten completion of the station. It also claimed that a joint
commission headed by Vice President Al Gore and Russian prime minister
Viktor Chernomyrdin "served chiefly to deny and cover up the delays
and cost overruns when they occurred." The report was widely
criticized by the Clinton Administration and other Democrats, calling
it a partisan broadside released less than two months before the
general election.
MirCorp Funds Progress Launch, Adjusts Schedule: MirCorp, the company
leasing the Mir space station for commercial use, announced late
Friday that it was paying for the launch next month of a third
Progress resupply spacecraft. The Progress will deliver fuel, air,
and other supplies for the station, allowing it to remain in operation
well into next year. At the same time, though, the company is
readjusting its schedule of manned missions to the station, shortening
the next crew's stay on Mir from several months to just two weeks.
Two cosmonauts will now fly to Mir early next year along with "citizen
explorer", or space tourist, Dennis Tito, and return two weeks later.
The cosmonauts were to have gone to the station themselves and spent
several months there before being relieved by a backup crew that would
have brought Tito along. Funding problems were cited for the change
in the schedule.
Dreamtime Problems: In an incident that may be best described as
bizarre, NASA rebuked Dreamtime, the agency's "multimedia partner",
last week after the California company talked with representatives of
three television networks about a series like "Destination Mir" that
would use the International Space Station. The company apparently
held discussions with ABC, CBS, and Fox about doing a show like the
one NBC bought the rights for earlier this month that will send one
person to the Mir space station. NASA officials, calling reports of
such discussions "shocking", told Dreamtime that it "shall, at no
time, represent or claim to represent NASA or act as NASA抯 agent,"
according to SPACE.com. NASA selected Dreamtime in June to be the
agency's multimedia partner, making available images and films in
NASA's archives to the public while providing high-definition video of
shuttle launches and ISS work.
Stars Orbiting Supermassive Black Hole: Astronomers reported last
week that they have, for the first time, observed stars orbiting a
supermassive black hole in the center of our galaxy. The
observations, carried out using the 10-meter Keck Observatory
telescopes and reported in the September 21 issue of Nature, show that
some stars are orbiting so close to the black hole that their
velocities have changed by a million miles per hour over the last four
years, enough to allow astronomers to see changes in their position.
The discovery is noteworthy since it allows astronomers to pin down
the location of the black hole to a higher precision than previously
possible. "We now know the location of the black hole so precisely,"
explained Andrea Ghez, an astronomer at UCLA, "that's it's like
someone in Los Angeles who can identify where someone in Boston is
standing to within just over a yard, if you scale it out to 24,000
light years."
*** Articles ***
The Rise and Fall of Martian Life
By Julian A. Hiscox
[Editor's Note: This article previously appeared in the BIS
publication Spaceflight as well as in the online publication Marsbugs.
It is reprinted here with the kind permission of the author.]
The surface of present day Mars is bathed in lethal ultraviolet
radiation and probably coated in a layer of peroxides and superoxides.
If terrestrial type life were sprinkled on the surface of Mars then it
would degrade to dust in a matter of minutes. Data from the two
Viking landers showed that no organic material is present on the
martian surface. However, analysis of one of the youngest SNC
meteorites indicated that organic material was at least stable below
the surface of Mars up until about 150 million years ago. Thus by all
accounts the climate of ancient Mars was far more conducive to life
than that of present day Mars. The conditions on the surface of Mars
have probably been unchanged for the past two billion years or so.
The origin of life on Earth -- let alone Mars -- has not been
elucidated. However, assuming life did arise on Mars, we can make a
number of speculations as to its fate. This will help guide future
searches for extinct or possibly extant life on Mars. Microbial life
on Earth has colonized all manner of niches, from the coldest, driest
places on Earth (the rock faces of the Antarctic dry valleys) to
thermal springs and hydrothermal vents where viable microorganisms
have been isolated living at 113 C (235 F). Therefore if life arose
on Mars, there are a number of potential habitats where such life may
have lived.
The Migration of Life on Mars
How life may have originated on Mars is unknown. However, life on
Mars may have arisen either at hydrothermal vents, in possible martian
oceans, or all manner of places where liquid water was stable and
energy was provided in some form. During the course of martian
history, components of hydrothermal centers could have interacted via
networks of intersecting faults and fractures. For example, a
quantity of water equivalent to a global layer 10 meters (33 feet)
deep is sufficient to saturate the lower-most 0.8 kilometers (0.5
miles) of the megaregolith, while a quantity of water equivalent to a
100 m (330 foot) layer would create a global aquifer nearly 43 km (26
mi.) deep.
Material could be moved within (and perhaps exchanged between)
aquifers by hydrothermal convection. This occurs when an aquifer is
heated locally, setting up density contrasts in the water and
initiating buoyancy-driven flow. On Earth today there are two major
sites of hydrothermal convection. First, associated with magmatism,
mainly at plate boundaries but also associated with plumes, and
second, on the deep sea floor where about twenty times as much water
circulates at rather low temperatures driven by heat residing in the
oceanic crust. With the possible absence of tectonic and large ocean
plates on early Mars, apart from the low temperature aqueous
convection in the crust, magmatic activity associated with plumes and
impact heating would have been drivers of hydrothermal convection.
Magmatic intrusions 1000 cubic kilometers (235 cubic miles) in size
could have circulated fluids continuously for about 105 years.
Aquifers drawn down by seepage could therefore have been replenished
for long periods as hydrothermal convection circulated water into
them. Small-scale fluvial activity decreased with time as hydrothermal
activity diminished and the atmosphere cooled, although local
hydrothermal systems could have accounted for the continuation of
isolated fluvial events well into post-Noachian times. However, some
volcanic units on Mars may be as young as 100,000 years. Thus the
nutrients for life and life itself would have continuously circulated
throughout any martian ocean or where liquid water was present beneath
the martian surface.
If liquid water was abundant, and large bodies of liquid water were
stable, then the migration of life toward the surface is relatively
easy to accomplish, as presumably rivers fed the ocean(s). Microbial
life would therefore have diffused onto the land. If liquid water was
not so abundant, the possibility remains that subsurface life could
also have spread to the surface of Mars. Assuming terrestrial
paradigms are valid, organisms may have been selected for that could
grow in brine or ice-covered lakes, which have been proposed as
possible habitats for ancient martian life. On Earth archeabacteria
have succeeded in colonizing waters of very high salinity, even the
saturated brine of drying seas: they are the only living organisms
that still inhabit the Dead Sea and the Great Salt Lake. The
detection of sulfur and chlorine and the presence of duricrusts in the
martian regolith suggest that brines may have been present on Mars in
the past but are precluded on present-day Mars.
The Decline of the Environment and the Implications for Life
As the atmospheric pressure decreased on Mars, conditions became
increasingly deleterious for any surface-based life. Imre Friedmann
and Chris McKay and also David Wynn-Williams have outlined four epochs
of "water" on Mars. The first three of which have readily
identifiable equivalent habitats found in Antarctica today. The four
epochs Wynn-Williams outlines in his paper in the British
Interplanetary Society's "The Search for Life on Mars" symposium
proceedings are described below:
Epoch 1. Abundant water. Probably necessary for an origin of life
event, whether above ground in an ocean or hot spring or deep below
the surface. Potential models for wide spread liquid water on Mars
are the seasonal melt-water rivers in Antarctica which support
photosynthetic cyanobacteria.
Epoch 2. Restriction of water to ice-covered lakes. Ice covered
lakes can be found in the Antarctic Dry Valleys whose surfaces are
frozen all year around. Yet colonies of bacteria live in the liquid
below the frozen surface. The temperature in such lakes is probably
too cold for an origin of life event to occur, as a hot start was
probably required. Therefore, life would have had to have had either
migrated to these environments or be "trapped" in them--once the
environment declined.
Epoch 3. Restriction of water to moisture within porous rocks (as in
the Antarctic Dry Valleys). In these environments microorganisms live
right at the edge of extinction. These organisms are already as
tolerant to desiccation as can be possible. Evolution and adaptation
can only go so far before the laws of thermodynamics intervene.
Epoch 4. Xeric surface of Mars. The surface of Mars is completely
hostile for life.
During the period when water was becoming less abundant on the surface
of Mars, possible surface organisms might have been selected for which
were tolerant of low temperatures and humidity. When the (near)
surface became uninhabitable only organisms that lived deep
underground would have survived, possibly in chemosynthetic
ecosystems. The penetration of the thermal wave of temperatures below
0 C (32 F) was almost certainly not uniform across the surface of
Mars. Hence, some parts of Mars may have become frozen before other
parts. The formation of ice would have effectively separated the net
transport, both vertically and horizontally between surface dwelling
and underground organisms. Also the potential absence of plate
tectonics on Mars might have resulted in the formation of two distinct
reservoirs of water.
Hence, there exists the exciting possibility of both spatial and
temporal distribution between different water sources and putative
life forms. The differences in freezing over Mars, presumably
progressing from pole to equator, may have preserved organisms that
were at different developmental stages, perhaps protocells to
unicellular life, and evidence of this might be found on present-day
Mars. Table 1 shows the different estimated ages of the martian
plains; it may be possible given their geographic distribution that
any remains of life could be preserved at different stages. Hesperia
Planum, the oldest plain, is situated approximately 20 degrees south
of the equator and may therefore have been one of the last places to
freeze, and thus may contain remnants of the most developed martian
organisms.
Exploring for Micro- and Molecular Fossils on Mars
Whether life could have continued in hydrothermal systems on Mars
until the present day can only be determined by direct sampling.
However, the longer life survived the more chance that an extensive
exobiology search has for locating trace fossils or biochemical
markers. Where would we look for such molecules? Mike Russell and
his colleagues at the University of Glasgow suggested that life might
have emerged from a far-from-equilibrium chemical system coupled to,
and driven by, hydrothermal convection. Even on Earth where our
oxygenated atmosphere supports a plethora of species, many
thermophilic bacteria remain obliged to live at hot springs and
seepages. Such coupling can guide our exploration for fossil evidence
of life on Mars.
Russell suggests that sulfide microbialites, a kilometer or so in
length and ten or so meters wide, generated at palaeo hot springs or
seepages, might be expected to occur over a fault. On Mars the
presence of canyons, channels and out wash fans provides the best
evidence for aqueous fluid flow, and it is likely that water continued
flowing through the detritus in the base of the channels during the
first billion years of the planet's history. The crust of Mars is
likely to be composed of mafic or ultramafic rock such as basalt or
komatite. Water, carbonated by the carbon dioxide in the early
atmosphere, or evolving directly from magma at depth, would have
reacted with the mafic debris as it percolated and gravitated to
inland seas or lakes, where the meteoric water may have emanated as a
buoyant plume. Russell has proposed that the terrestrial site that
might provide us the indication of what to expect at such an effluence
on Mars is revealed in the Alpine ophiolites, portions of basaltic
ocean crust thrust over Eurasia.
Some scientists have postulated that the remains of organic compounds
on present day Mars might provide clues as to which combination of
compounds lead to life and which did not. Although such a question
may be unanswerable since different compounds degrade at different
rates. Thessa Kanavarioti and Rocco Mancinelli, both at NASA Ames
Laboratory, suggested that if organic matter such as amino acids
existed on Mars 3.5 billion years ago ago then traces that are
preserved below the surface oxidizing layer might still be present.
Only if the amino acids were located in aqueous or frozen subsurface
deposits, such as polar regions, would racemization have been
preserved. (All terrestrial life uses one isomer of amino acids for
metabolism). Without which it would be very difficult to determine
whether the amino acids were of abiotic or biotic origin.
In addition, Jeffrey Bada, based upon his estimate of aspartic acid
racemization on Mars, suggested that nucleic acid information might
also be preserved on Mars under similar conditions as amino acids.
However, experimental data indicate that ribose, which makes up the
backbone of nucleic acids, has an extremely short half-life:
approximately 44 years at 4 C (39 F). Therefore genetic information
based upon a ribose back bone might not be expected to be found in the
same location as amino acids, if at all, even if they were originally
present together. Chris McKay and Wanda Davis of NASA Ames suggest
that the location of the remains of ice covered lakes which may have
persisted during times of climatic hostility would increase the
probability of amino acids being preserved until present day.
Summary
Climatic conditions on early Mars are thought to have resembled some
of the conditions on early Earth, thus giving weight to the idea that
life may also have arisen on Mars. There are many theories that have
been proposed to explain the origin life on Earth, none of which can
be proven, and because of its geology Mars provides a unique
opportunity to investigate this. Indeed it may be possible that more
than one origin of life event occurred on Mars. If life arose on Mars
by hydrothermal mechanisms the possibility arises that multiple origin
of life centers may have occurred on Mars, and because large bodies of
liquid water may have been absent, such centers may have been
geographically isolated, thus giving rise to different lineages of
life.
Recommended reading:
Carr, M. H., Water on Mars. Oxford University Press, New York (1996).
Davis, W. L., and C. P. McKay, "Origins of Life: A comparison of
theories and applications to Mars", Origins of Life and Evolution of
the Biosphere, 26, 61-73, (1996).
Hiscox, J. A. (Ed), The Search for Life on Mars. British
Interplanetary Society, London (1999).
McKay, C. P., and C. R. Stoker, "The early environment and its
evolution on Mars: Implications for life", Reviews of Geophysics, 27,
189-214, (1989).
McKay, C. P., E. I. Friedmann, R. A. Wharton, and W. L. Davis,
"History of water on Mars: A biological perspective", Advances in
Space Research, 12(4), 231-(234)238, (1992).
Table 1. Ages of martian plains as estimated by Mike Carr of the
United States Geographical Survey and the equivalent development of
life on Earth and possibly Mars.
Plains region Age in billion years Stage of life on Earth
Best est. Range (relative to best estimate)
Mare Acidalium 1.2 0.2-1.7 Increase in diversity
Sinai Planum 1.4 0.4-3.0 Origin of eukaryotes
Utopia Plantia 1.8 0.6-2.3 Youngest detrital
uraninites
Noachis
Planitia 2.5 0.9-3.6 Oldest heterocyst like cells
Amazonis
Planitia 2.8 1.0-3.7 As below.
Syrtis Major
Planum 2.9 1.2-3.7 Diversification of
anaerobic prokaryotes
Chryse
Planitia 3.0 1.2-3.8 Oldest stromatolites
Lunae Planum 3.5 1.7-3.8 Oldest fossils
Hellas 3.8 2.9-3.9 Earliest biogenic activity
(Life on Mars? ALH84001)
Hesperia
Planum 3.9 3.0-3.9 Origin of life on Earth
Dr. Julian A. Hiscox (J.A.Hiscox@reading.ac.uk) is with the School of
Animal and Microbial Life at the University of Reading, UK.
========
This has been the September 25, 2000, issue of SpaceViews.
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