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These gullies on a Martian sand dune resemble features on Earth that are carved by water. However, they were likely formed by processes related to the winter buildup of carbon-dioxide frost, according to a new study. The top photo was taken in March 2008 (Martian autumn), the middle one in July 2009 (summer) and the bottom photo in October 2010 (winter). All were taken by NASA's Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/University of Arizona [Full Story] |
Some of the
mysterious gullies on Mars are likely carved by frozen carbon dioxide, not
melting water, a new study finds.
Researchers tracked
recent changes in sand dune gullies in seven different locations on southern Mars.
They found that these changes ? which occurred over the past 15 years or so ?
popped up most often in winter, which is consistent with the buildup of carbon
dioxide frost, not runoff from melting water. [Photos
of Martian gullies.]
"Gullies that
look like this on Earth are caused by flowing water, but Mars is a different
planet with its own mysteries," said study lead author Serina
Diniega of NASA's Jet Propulsion Laboratory in
Pasadena, Calif. "The timing we see points to carbon dioxide, and if the
mechanism is linked to carbon dioxide frost at these dune gullies, the same
could be true for other gullies
on Mars."
Hunting Mars gullies
Diniega analyzed the gullies
while a graduate student at the University of Arizona, before joining NASA at
JPL. She and her team studied a set of gullies in southern regions of Mars. The
channels range in length from 165 feet (50.3 meters) to more than 2 miles (3.2
km).
The researchers
tracked changes in the gullies by comparing photos taken at various times by
two different NASA spacecraft: the Mars Global Surveyor, which operated from
1997 to 2006, and the Mars Reconnaissance
Orbiter, which has been circling Mars since 2006.
The team spotted
changes in 18 different gullies. These alterations occurred primarily in the
southern Martian winter, when frozen carbon dioxide would be building up on the
dunes.
Photos taken in
spring, summer and autumn ? times when water could conceivably be melting and
running down dune faces ? showed no new activity, researchers said.
The research is
detailed in the November issue of the journal Geology.
Landscape shapers:
Water then, carbon dioxide now?
Scientists have
suggested various explanations for modern gullies on Mars since they were
discovered in 2000. Some of the proposed mechanisms involve water, some carbon
dioxide and some neither.
Scientists believe
water has covered the surface of Mars at various points in the distant past. Ancient
seas, for example, could explain why the planet's northern
lowlands hold extensive sedimentary deposits that resemble those seen in the
abyssal plains of Earth's ocean floors.
Today, however, the
Red Planet is cold and dry. It has deposits
of water ice, but scientists haven't confirmed areas with liquid
water currently on the surface.
The new results
suggest carbon dioxide could be shaping the Martian landscape today ? and they
call for further study into how this could be happening, researchers said.
"One possibility
is that a pile of carbon dioxide frost accumulating on a dune gets thick enough
to avalanche down and drag other material with it," Diniega
said. Other suggested mechanisms are that gas from sublimating frost could
lubricate a flow of dry sand or erupt in puffs energetic enough to trigger
slides, researchers added.
- Gallery:
Water on Mars Imagined
- Top 10 Facts About
NASA's Mars Reconnaissance Orbiter
- Oceans
of Ancient Mars May Have Sprung From Slow Leaks
