[meteorite-list] Gullies on Mars Show Tantalizing Signs of Recent Water Activity

From: Erik Fisler <erikfwebb_at_meteoritecentral.com>
Date: Mon, 2 Mar 2009 22:24:49 -0700
Message-ID: <COL119-W39257E758053A360207960A4A60_at_phx.gbl>

Thanks Ron! I needed this artical for my curent astronomy event in my astronomy class.
Can anyone give me an opinion on this for me to quote?
 
[Erik]

> From: baalke at zagami.jpl.nasa.gov
> To: meteorite-list at meteoritecentral.com
> Date: Mon, 2 Mar 2009 14:40:47 -0800
> Subject: [meteorite-list] Gullies on Mars Show Tantalizing Signs of Recent Water Activity
>
>
>
> Media Relations
> Brown University
>
> Contact:
> Richard Lewis, (401) 863-3766
>
> March 2, 2009
>
> Gullies on Mars Show Tantalizing Signs of Recent Water Activity
>
> Brown planetary geologists have located a gully system that appears to have
> been carved by melt water that originated in nearby snow and ice deposits.
> The gullies, which the team determined to be about 1.25 million years old,
> may represent the most recent period when water flowed on the planet. The
> findings appear on the cover of the March issue of Geology.
>
> PROVIDENCE, R.I. -- Planetary geologists at Brown University have found a
> gully fan system on Mars that formed about 1.25 million years ago. The fan
> offers compelling evidence that it was formed by melt water that originated
> in nearby snow and ice deposits and may stand as the most recent period when
> water flowed on the planet.
>
> Gullies are known to be young surface features on Mars. But scientists
> studying the planet have struggled with locating gullies they can
> conclusively date. In a paper that appears on the cover of the March issue
> of Geology, the Brown geologists were able to date the gully system and
> hypothesize what water was doing there.
>
> The gully system shows four intervals where water-borne sediments were
> carried down the steep slopes of nearby alcoves and deposited in alluvial
> fans, said Samuel Schon, a Brown graduate student and the paper's lead
> author.
>
> "You never end up with a pond that you can put goldfish in," Schon said,
> "but you have transient melt water. You had ice that typically sublimates.
> But in these instances it melted, transported, and deposited sediment in the
> fan. It didn't last long, but it happened."
>
> The finding comes on the heels of discoveries of water-bearing minerals such
> as opals and carbonates, the latter of which was announced by Brown graduate
> student Bethany Ehlmann in a paper in Science in December. Those discoveries
> build on evidence that Mars was occasionally wet far longer than many had
> believed, and that the planet may have hosted a warm, wet environment in
> some places during its long history.
>
> However, the finding of a gully system, even an isolated one, that supported
> running water as recently as 1.25 million years ago greatly extends the time
> that water may have been active on Mars. It also adds to evidence of a
> recent ice age on the planet when polar ice is believed to have been
> transported towards the equator and settled in mid-latitude deposits, said
> James Head III, professor of geological sciences at Brown, who first
> approximated the span of the martian ice age in a Nature paper in 2003.
>
> "We think there was recent water on Mars," said Head, who with Brown
> postdoctoral researcher Caleb Fassett is a contributing author on the paper.
> "This is a big step in the direction to proving that."
>
> The gully system is located on the inside of a crater in Promethei Terra, an
> area of cratered highlands in the southern mid-latitudes. The eastern and
> western channels of the gully each run less than a kilometer from their
> alcove sources to the fan deposit.
>
> Viewed from afar, the fan appears as one entity several hundred meters wide.
> But by zooming in with the HiRISE camera aboard the Mars Reconnaissance
> Orbiter, Schon was able to distinguish four individual lobes in the fan, and
> determine that each lobe was deposited separately. Moreover, Schon was able
> to identify the oldest lobe, because it was pockmarked with small craters,
> while the other lobes were unblemished, meaning they had to be younger.
>
> Next came the task of trying to date the secondary craters in the fan. Schon
> linked the craters on the oldest lobe to a rayed crater more than 80
> kilometers to the southwest. Using well-established techniques, Schon dated
> the rayed crater at about 1.25 million years, and so established a maximum
> age for the younger, superimposed lobes of the fan.
>
> The team determined that ice and snow deposits formed in the alcoves at a
> time when Mars had a high obliquity (its most recent ice age) and ice was
> accumulating in the mid-latitude regions. Sometime around a half-million
> years ago, the planet's obliquity changed, and the ice in the mid-latitudes
> began to melt or, in most instances, changed directly to vapor. Mars has
> been in a low-obliquity cycle ever since, which explains why no exposed ice
> has been found beyond the poles.
>
> The team tested other theories of what the water may have been doing in the
> gully system. The scientists ruled out groundwater bubbling to the surface,
> Schon said, because it seemed unlikely to have occurred multiple times in
> the planet's recent history. They also don't think the gullies were formed
> by dry mass wasting, a process by which a slope fails as in a rockslide. The
> best explanation, Schon said, was the melting of snow and ice deposits that
> created "modest" flows and formed the fan.
>
> NASA funded the research.
>
> IMAGE CAPTIONS:
>
> [IMAGE 1:
> http://news.brown.edu/files/article_images/Schon%20Mars%20gullies%20Zoom%20in.jpg
> (1.2MB)]
> The gully system in the Promethei Terra region of Mars appears to have been
> carved by melt water and may be the most recent period when water was active
> on the planet. Credit: NASA/JPL/University of Arizona
>
> [IMAGE 2:
> http://news.brown.edu/node/10408]
> The gully system shows four distinct lobes. Credit: NASA/JPL/University of
> Arizona
>
> ______________________________________________
> http://www.meteoritecentral.com
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Tue 03 Mar 2009 12:24:49 AM PST