For this newly studied gully system, the evidence of multiple outflows discredits drifting sands, and the classic alluvial pattern of the delta does not fit with sedimentary shifts, Schon says. Jack Holt, a geophysicist at the University of Texas at Austin, agrees "melting an ice deposit caused by an ice age seems like a more feasible scenario."
Mars has an axial tilt (similar to Earth's) that causes seasons, but the Red Planet wobbles more on its axis than Earth does because it lacks the gravitational stabilization that our relatively large moon provides. Coupled with a more elliptical orbit than Earth, Mars likely has major swings in climate and temperature over short spans of geologic time. Other recent discoveries, including massive Martian glaciers still present under blankets of crustal debris in the mid-latitudes, support theories of past ice ages on the Red Planet.
"This new study is yet more strong evidence for widespread deposition of ice during a different climatic regime," says Holt, who led the glacier work.
Due to frigid surface temperatures and low atmospheric pressure, liquid water could not persist for long on Mars's surface nowadays. But scientists continue to hunt for signs of liquid water in the recent and distant past—not least for the clues they may provide about the possible development of extraterrestrial life when Mars's climate was more hospitable.
"We think the heyday for water on Mars was over three billion years ago," Schon says. "With this gully system, we're talking about a relative trickle compared to then, but nonetheless, this happened, and now we know when."
See what we're tweeting about
8 Comments
Add CommentPeople used to think those were canals built by intelligent Martians to carry water. :)
Reply | Report Abuse | Link to thisI fell asleep watching Sagans Cosmos last night. Had a big dream about prehistoric mars. I can't help but wonder if there's a possibility that life was knocked off Mars during it's inhabitable period and arrived on earth. Possibly by a cosmic collision, or possibly by experimenting scientists of that era, from there or elsewhere. If our sun was fading and our planet was about to freeze and lose its atmosphere, would we not try to send off the seeds of life to any nearby planet that may be habitable? Hm. It's not immediately productive to think about such things, but it is entertaining.
Reply | Report Abuse | Link to thisThe gullies are quite a bit smaller (kilometer-scale) than the valley networks (many hundreds of kilometers). While valley networks strongly suggest pluvial activity and integrated catchments early in Mars history (>3 billion years ago), the gullies seem to represent transient/ephemeral flows of water in the very recent past.
Reply | Report Abuse | Link to thisThe original article in Geology is here:
http://geology.gsapubs.org/cgi/content/full/37/3/207
The assumption here is that the secondary craters once covered a larger area of the photo but were washed away by the later water flow. I don't see any craters on the far side of the gully. Is it possible that the craters we see in the picture simply represent the farthest extent of the area where the material was ejected from the meteor strike? In that case, the craters could be the more recent feature.
Reply | Report Abuse | Link to thisIt's clear, from the photo, that the major cities and other infrastructures were washed away in the thaw!
Reply | Report Abuse | Link to thisImagine the loss to humanity: If only Great Library of Mars had survived!
What wonders we could learn. Shame it's gone.
Since Mars and Earth are the same age, early life might have been "knocked off" Mars (to the Earth), but how did it start on Mars?? Also, When the Sun "fades", it will swell up and incinerate the Earth, we won't have to worry much about freezing.
Reply | Report Abuse | Link to thisResponding to Josh83 :
Reply | Report Abuse | Link to thisInteresting suggestion but from the text: the gully system is ~1km in size but the crater which generated the impacting rocks is ~100km away (~100 times as large; meaning the rocks rained down over an area at least 200km wide). It's very unlikely that such a widely-dispersed rain of rocks would happen to end partway across such a relatively small feature - you'd expect a gradual dropoff not a sudden one, and any sudden dropoff would be very unlikely to occur at that exact location.
Yes Cosmos gets like that :-)
Reply | Report Abuse | Link to thisThe obvious response is that we know that life arose (somehow) on Earth but we have no convincing evidence that this happened on Mars or that life which did arise there was transferred (the famous ALH84001 meteorite results which suggested that at least Martian fossils could reach Earth are generally regarded as unreliable).
By Occam's Razor which Carl Sagan was fond of (basically "All other things being equal, the simplest explanation consistent with the facts is likely to be the right one") it makes more sense to assume that life found on Earth started on Earth, until proven otherwise.
As far as humans seeding life elsewhere goes : this is a very good reason to colonise other lifeless planets, but alas I don't think we'll live to see it.