Basic Astronomy

Curiosity found evidence of ancient river bed in Mars

27 September 2012: Curiosity rover mission of NASA has found a place with evidences of a stream that once ran across the area on Mars. With the help of telephoto capability of Curiosity's mast camera, after summarizing data of the first 40 days after landing, Curiosity found a place which was a river bed long ago.

Mars conglomerate.
(Image Credit: NASA/JPL-Caltech/MSSS and PSI)

"Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of stream bed material to direct observation of it," said Curiosity co-investigator William Dietrich of the University of California.

Scientists are now examining the images of stones which are cemented into a layer of conglomerate rock. The shapes and sizes of these stones offer important clues to the distance and speed of a ancient flow of a stream. "From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth some where between ankle and hip deep," explained William Dietrich. The rocks were likely created "several billion years ago". But it is possible that the actual streams may have persisted on the surface even for longer time, added Dietrich. "We would anticipate that it could easily be thousands to millions of years," told Dietrich.

This stone gravels are found between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater.

Curiosity
This set of images compares the rocks on Mars (left) with similar rocks seen on Earth (right). (Image Credit: NASA/JPL-Caltech/MSSS and PSI)

A channel of water, named Peace Vallis, feeds into the alluvial fan. The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim.

There are high abundance of channels in the fan between the rim and conglomerate. This suggests that the flows was not just once or for few years, it continued or repeated over a long time.

The Curiosity found the evidence of water flow in two outcrops called "Hottah" and "Link". There were some evidences of presence of water in Mars, specially in pole region of the planet but this new evidence of images of rocks containing ancient stream bed gravels is directly shows presence of water in this planet.

"Hottah looks like someone jack-hammered up a slab of city side walk, but it's really a tilted block of an ancient stream bed," said Mars Science Laboratory Project Scientist John Grotzinger of Caltech in Pasadena. There are different sizes of gravels in conglomerates at both outcrops - the size varies from size of a grain of sand to a golf ball. Some of these gravels are angular but many of them are rounded.

"The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind. They were transported by water flow," said Curiosity science co-investigator Rebecca Williams.

Next, science team is planning to study the elemental composition of the materials, which holds the conglomerate together. This will certainly reveal more properties of the wet environment that formed these deposits.

The Curiosity rover will study in near future the slope of Mount Sharp in Gale Crater. Orbital missions detected clay and sulfate minerals in this region and this area can be good preservers of carbon-based organic chemicals which are important ingredients for life.

"A long-flowing stream can be a habitable environment," explained Grotzinger. "It is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."

In past, images from orbital satellites shown evidence of channels on the Mars surface that were cut by some kind of flow. There were different model to explain formation of these channels, ranging from flow of water in past, huge air flow and volcanic eruption. Curiosity new observation at its landing site in the equatorial Gale Crater gives us important support of the fact that in past there was indeed flow of water.

Past satellite images of this region hinted presence of water in this region. Conglomerates found by Curiosity supports that hypothesis.

Curiosity science team will study whether in past the areas in Gale Crater have offered environmental conditions favorable for microbial life.

Scientist will also study the chemistry of the conglomerates which will give an indication of the nature of the water and that will give some hint of the past environment of the region.











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