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| Saturn's moon Titan in natural color. (Photo credit: Wikipedia) |
NASA's researchers find thousands of craters on Titan being filled in by windblown sand
A naturally occuring makeover on the surface of Saturn's largest moon
is erasing thousands of craters that pockmark the surface which
scientists were using to determine its age.
NASA researchers made the discovery from observations made by the
Cassini spacecraft, sent to explore the neighbourhood surrounding the
ringed-planet back in 2004.
According to NASA's findings, the craters on Saturn's moon Titan are
slowly being filled in with hydrocarbon sand, which seems to be coming
from some sort of methane source.
"Most of the Saturnian satellites – Titan's siblings – have thousands
and thousands of craters on their surface," said Catherine Neish, of
NASA's Cassini radar team.
"So far on Titan, of the 50 per cent of the surface that we've seen in high resolution, we've only found about 60 craters."
Neish said her team made the discovery after comparing craters on Titan with those of Jupiter's moon Ganymede.
The two moons both have an ice crust, which in theory, should have meant they shared similar crater shapes.
"We found that craters on Titan were on average hundreds of metres
shallower than similarly sized craters on Ganymede, suggesting that some
process on Titan is filling its craters," said Neish.
"This suggests a process like windblown sand, which fills craters and
other features at a steady rate," said Neish, explaining why Titan's
are being filled.
Hydrocarbon sand
But what still has Neish and her team puzzled is the source of methane that is contributing to the sand's formation.
The researchers said that methane, which typically breaks down
quickly from sunlight, is forming into more complex hydrocarbons in
Titan's upper atmosphere. Larger particles then rain onto the moon's
surface and bind together forming the sand.
"Since the sand appears to be produced from the atmospheric methane,
Titan must have had methane in its atmosphere for at least several
hundred million years in order to fill craters to the levels we are
seeing," said Neish.
The other option might be that Titan either has more methane in its
atmosphere then previously estimated, or has some way replenishing it
now.
To date, Cassini has provided data covering approximately 50 per cent
of Titan's surface, and within 30 degrees of its equator. The
spacecraft is on a multi-year tour of Saturn and its moons.
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