Gullies on Mars show water ran on Red Planet as early as 1.25 mln yrs ago

March 3rd, 2009 - 12:55 pm ICT by ANI  

Washington, March 3 (ANI): Planetary geologists at Brown University, US, have found a gully fan system on Mars that formed about 1.25 million years ago, which shows tantalizing signs of recent water activity on the Red Planet.

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 research 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 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.

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 papers lead author.

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, according to James Head III, professor of geological sciences at Brown University, 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, he added.

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. (ANI)

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