& SCIENCE NEWS: March 2003
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& science news > space & science news: March 2003
Martian biology in plain view?
(Mar 28, 2003)
There are dangers in reading too much into surface markings on other
worlds – remember Percival
Lowell and the saga of the Martian
canals? However, there's mounting interest, not just among eager
amateurs armed with downloaded NASA images and PCs, that something
is happening on Mars that points to movements of liquid on or near
the surface and possibly even the coming and going of life itself.
The latest surge in speculation centers on certain dark streaks (see
also the article below this one) that have appeared from nowhere over
a period measured in months. Reporting her research at the 34th Lunar
and Planetary Science Conference (LPSC), held March 17-21, 2003, in
Houston, Texas, Tahirih Motazedian, a student at the University of
Oregon, believes the streaks are caused by small amounts of liquid
water flowing in regions that are geothermally active. David McKay,
a NASA space scientist at the Johnson Space Center, went further at
the conference, and suggested that the dark coloration of the stains
may be due to colonies of microorganisms that are rejuventaed from
their normally dormant state by the sudden availability of water.
Although he acknowledges there may be other explanations, he says
"it seems to me that with our current data we cannot exclude it."
This adds credence to the claims of Hungarian researchers Tibor Ganti
and Andras Horvath, who also attended this month's LPSC and presented
evidence of a link between water near the surface of Mars and the
formation of so-called "dark dune spots" (DDSs). Since 1998, they
have plotted the regular appearance and disappearance of DDSs, and
have reached the conclusion that the spots point to "some kind of
biological activity of putative Mars surface organisms, acting on,
or in, the material of the dark dunes."
For more, see this
article (space.com), the Astrobiology Encyclopedia entries for
life on Mars, and these earlier news stories: Mystery
spots deserve closer look and Hungarian
claims of vegetation on Mars.
Strongest evidence yet for water flows
(Mar 13, 2003)
New images and analysis suggest that the slopes around Mars'
biggest volcano, Olympus Mons, bear dark stains caused by briny water
flowing downhill. The new results suggest that underground ice deposits
can sometimes melt and flow across the surface and add enormous weight
to increasing speculation that life
may exist near the planet's surface. According
to Tahirih Motazedian of the University of Oregon, it is the first
time that changes on Mars have been seen due to water. She has examined
images of Mars taken at different times and has seen new streaks form
within a period of months. She speculates that geothermal activity
driven by volcanic heat may be causing the melting of subsurface ice.
The water dissolves surrounding minerals to form a super-salty solution
that can remain liquid at much lower temperatures and pressures than
pure water can. When the brine trickles onto the surface, it flows
downhill staining the surface.
"The streaks originate from distinct geologic horizons below the Martian
surface, where the water/ice table has been intersected by crater
and valley walls," Motazedian says. Significantly, the dark streaks
are never overlain or cut by other features like craters or sand dunes.
Instead, they passively overlay existing features except where they
are forced to flow around obstacles. The dark streaks always begin
upslope as points, then widen downhill, just like flowing water. Images
taken of the Mangala Valles region show that the dark streaks are
being formed at the present time. Two images taken a few months apart
show new streaks have appeared.
Jovian moons galore
(Mar 7, 2003)
Seven new moons have been found around Jupiter,
bringing the big planet's satellite tally to 47. Saturn is now a distant
second with 30. Jupiter's new satellites were discovered in early
February 2003 by Scott Sheppard and David Jewitt of the University
of Hawaii, working with Jan Kleyna of Cambridge University, and publicly
announced on March 4. They were found using the world's two largest
digital cameras at the 8.3-meter Subaru Telescope and the Canada-France-Hawaii
3.6-meter telescope on Mauna Kea in Hawaii. The new moons are all
small, two to four kilometers across, and orbit Jupiter at distances
ranging from about 11 million to more than 24 million km. Two of the
seven new satellites (S/2003 J1 and S/2003 J6) have an orbit around
Jupiter that is in the same direction as Jupiter's spin. The other
five have distant retrograde orbits like the majority of the known
irregular satellites of Jupiter. My encyclopedia entry for Jupiter's
includes the previously known 40 moons and will be updated to include
the seven new ones as soon as possible.
For comprehensive, up-to-date information on all the known Jovian
moons, visit Scott Shepard's pages here.
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