New Evidence Suggests Icebergs In Frigid Oceans On Ancient Mars

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New Evidence Suggests Icebergs in Frigid Oceans on Ancient Mars
By Charles Q. Choi
SPACE.com Contributor
posted: 01 October 2010
08:41 am ET
Ancient Mars once had surprisingly frigid primeval oceans complete with their own icebergs, new evidence suggests.

There are currently two leading ideas for what the climate of ancient Mars might have been like.

One is that it was cold and dry, contending that valley networks and other geological features suggestive of liquid water in Mars' past were essentially results of bursts of heat confined in space and time, suggesting that Mars could not have sustained oceans. The other is that Mars was once warm and wet, implying that it could once have supported lakes, seas and rainfall for long periods.

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Now researchers have found evidence of icebergs on Mars, supporting a third idea of the Red Planet's ancient climate — that of a cold and wet Mars, governed by oceans or seas covered partly in ice, as well as glaciers and massive polar caps. [Photo evidence of past Mars icebergs.]

Boulder and craters

To peer into Mars' climatic past, scientists focused on the flat, smooth, featureless Martian lowlands, which some have equated to an ancient ocean basin.

However, images captured by the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter revealed the presence of boulders about 1.5-6.5 feet (0.5-2 meters) across, as well as chains of roughly one or two dozen craters measuring 330-1,300 feet (100-400 meters) wide scattered throughout the northern plains. Both these details are hard to reconcile with the notion of fine-grained sediments deposited on a deep ocean basin, and had been used to cast doubts on the concept of an ocean on Mars.

Now astrobiologist Alberto Fairen at the SETI Institute and NASA Ames Research Center and his colleagues suggest the presence and distribution of these boulders and chains of craters could have been caused by rock fragments carried by icebergs, a common process on Earth.

They suggest glaciers in the highlands could have eroded the terrain, transporting rock within them and on their surfaces. Armadas of icebergs would have formed at the edges of glaciers as they melted and broke apart, which could then float thousands of miles on the ocean before they disappeared, depositing rock downward.

Also, on Earth, when icebergs scrape against the ocean floor, they can rain boulders down in clumps, which could explain boulder clusters up to about a mile (1.6 km) wide that scientists have seen on Mars. In addition, when icebergs roll along the sea floor on Earth, they can generate strings of dents, perhaps explaining the chains of craters seen on the Martian lowlands.

Seas or oceans

If there were icebergs, then there were open and sizable bodies of stable liquid water on the surface of Mars, Fairen said.

"The size of the water bodies may have ranged from several local seas to a single hemispheric ocean, and they may have been continuous in time or episodic," he told SPACE.com.

Some might suggest that the scattered boulders were deposited by so-called periglacial processes, Fairen said — that is, processes that take place at the edges of glaciers. However, such processes cannot give a satisfactory explanation for the boulder clusters that HiRISE also saw, he noted.

Others have also suggested that the crater chains were formed by volcanic processes.

"But our analyses can discard this hypothesis, especially because all the craters within one chain are almost identical in shape and dimensions, and that's neither expected nor usual in a volcanic process, but is expected if all the craters in the chain are carved by the same iceberg," Fairen explained.

Fairen added that scour marks some 0.6 to 3 miles (1 to 5 km) long seen in the northern plains and Hellas Basin of Mars could be evidence of icebergs as well. These could have been carved by the keels of icebergs scraping against the ocean floor.

"The scours are the most clear evidence for icebergs that we are finding," he said.

Fairen and his colleagues detailed their findings at the 2010 Astrobiology Science Conference in April.

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posted 01 October 2010, 7:37 am ET
01speed21 wrote:
So bumps caused by boulders are suppose to have survived the receding of the oceans and millenia of erosion?
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posted 01 October 2010, 7:56 am ET
MartianSam1 wrote:
If this turns out to be true, that's really amazing - a block of ice millions of years ago floating in an ocean and melting would leave something that could be seen from orbit today.

I remember flipping over a rock in the desert and finding perfectly preserved centipede footprints from the Jurrasic period. The bug forgot the footprints but the sand never did. I love stuff like this. It's like finding little treasures in the attic that your grandparents left you.
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posted 01 October 2010, 8:09 am ET
Sehala wrote:
It's not unthinkable that these "bumps" could survive the oceans' receding and millenia of erosion. The craters were probably buried in sediment in the millenia following their formation, well before the oceans receded, and they were only uncovered recently (in geological terms) by millenia of winds eroding the sediment. Much in the same way that delicate fossils have survived for millenia on Earth only to be later uncovered by erosion.
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posted 01 October 2010, 9:34 am ET
rlb2 wrote:
Another factor is at the bottom of these glaciers today may be a film of water just like what happened on earth, see this new article on movements of glaciers.

http://www.msnbc.msn.com/id/39422259/

That being said other worlds that have icy surfaces and past evidence of glaciers, in particular Mars would have similar effect. Therefore water at the bottom of these glaciers on other worlds could support subterranean microbial life no matter what the surface temperature or atmospheric temperature is, case in point Enceladus and Europa.....
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posted 01 October 2010, 10:10 am ET
GeoDude wrote:
These features would have been left in shallow water, so they likely would have been near the edge of an ocean or deposited near the end of the ocean's existence. The article makes it sound like they have know about these features for awhile. I'm surprised anyone with geologic training would doubt that these were made in the presence of water, one look at the photo and it was pretty obvious what was going on. Do they not have geologists looking at these photos? They are quoting an astrobiologist on glacial processes, what's going on here NASA? Do you need to hire some people who have actually had training in identifying these types of landforms and processes? Sounds like they need to hire a geologist who specializes in glacial processes.
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posted 01 October 2010, 11:15 am ET
gordon_flash wrote:
If the MSSS website is still up then a look at many of the hi-res photos reveals many glacial features, and some features that may be rock glaciers that are active today. There was also, about a year or two ago, a photograph of Mars released by the European orbiter showing what looked all the world like huge icebergs (dust covered) floating in a sea. I don't believe for a minute that the 'bergs were floating in a liquid at present, but I could easily imagine they did at some point in the past.

One cannot discount the photos released showing exhumed deltas, either. Deltas don't form overnight. It takes time for the distributary channels to develop and it takes time for them to tear themselves down so new ones can form.

So, the conclusions reached in the article aren't surprising. The question is: how wet and how cold?
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posted 01 October 2010, 1:49 pm ET
nubsyn wrote:
I hope the first manned mars mission includes geologist, archaeologist, and a microbiologist. It would be a waist to send just a pilot, engineer and a chef!
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posted 01 October 2010, 3:36 pm ET
Jim_LAX wrote:
nubsyn: Of the 4 or 5 people sent, most should be scientists as you suggest. They should also be cross-trained in pairs for certain critical skills such as 2 pilots, 2 medics and 2 with Mr Fixit skills for electronic and mechanical repairs. And maybe one person who lived through the 60's so they can tell us how groovey it is on Mars.
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posted 01 October 2010, 5:54 pm ET
LavaMan wrote:
Hello All!
This image is one I'm just a tad familiar with since I'm the volcanologist on the MRO HiRISE team. These features are actually the result of steam exploding through a lava flow. Hot lava flowed over ground that had either ice or water in it. The heat from the lava boiled the water and it escaped by punching through the flow. The cones are in long chains because the top of the lava flow was moving over the site where the steam was being generated. This is discussed in good detail in an article published in 2007. My colleagues and I used this very image in a paper published earlier this year. Most of you won't have free access to those publications, but you can get more info at http://hirise.lpl.arizona.edu/ESP_018747_2065 (which discusses a nearby image) and http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2428.pdf which discusses this specific image. And we have also found that the frozen sea reported by HRSC in 2005 is actually a frozen sea of lava, not water. Hope that helps!
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posted 01 October 2010, 6:00 pm ET
bc wrote:
Lets just go there and look and see what it is all about...
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