Gamma-Ray Evidence Suggests Ancient Mars Had Massive Oceans

ScienceDaily (Nov. 18, 2008) — An international team of scientists who analyzed data from the Gamma Ray Spectrometer onboard NASA's Mars Odyssey reports new evidence for the controversial idea that oceans once covered about a third of ancient Mars.

We compared Gamma Ray Spectrometer data on potassium, thorium and iron above and below a shoreline believed to mark an ancient ocean that covered a third of Mars' surface, and an inner shoreline believed to mark a younger, smaller ocean,

said University of Arizona planetary geologist James M. Dohm, who led the international investigation.

Our investigation posed the question, Might we see a greater concentration of these elements within the ancient shorelines because water and rock containing the elements moved from the highlands to the lowlands, where they eventually ponded as large water bodies?

Dohm said.

This 3D map superimposes gamma-ray data from Mars Odyssey's Gamma-Ray Spectrometer onto topographic data from the laser altimeter onboard the Mars Global Surveyor. The red arrow indicates the shield volcanoes of Elysium rise in northern Mars, seen obliquely to the southeast. Blue-to-violet colors at the Elysium rise and highlands stretching to the foreground of the map mark areas poor in potassium. Red-to-yellow colors mark potassium-rich sedimentary deposits in lowlands below the Mars Pathfinder landing site (PF) and Viking 1 landing site (V1). (Credit: Image courtesy of University of Arizona)
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GRS: The Gamma Ray Spectrometer
The gamma ray spectrometer has measured the abundance and distribution of many elements of the periodic table, including hydrogen, silicon, iron, potassium, thorium, and chlorine. Knowing what elements are at or near the surface gives detailed information about how Mars has changed over time. To detmine the elemental makeup of the martian surface, the experiment uses gamma ray spectrometer and two neutron detectors.

A word from GRS' lead scientist
marsprogram.jpl.nasa.gov...
This map is based on gamma rays from the element hydrogen on Mars.
Image Credit: NASA/JPL/UA

How GRS Works

When exposed to cosmic rays (charged particles in space that come from the stars, including our sun), chemical elements in soils and rocks emit uniquely identifiable signatures of energy in the form of gamma rays. The gamma ray spectrometer looks at these signatures, or energies, coming from the elements present in the Martian soil.

By measuring gamma rays coming from the martian surface, it is possible to calculate how abundant various elements are and how they are distributed around the planet's surface. Gamma rays, emitted from the nuclei of atoms, show up as sharp emission lines on the instrument's spectrum. While the energy represented in these emissions determines which elements are present, the intensity of the spectrum reveals the elements concentrations. The spectrometer has added significantly to the growing understanding of the origin and evolution of Mars and the processes shaping it today and in the past.

marsprogram.jpl.nasa.gov...

How are gamma rays and neutrons produced by cosmic rays? Incoming cosmic rays--some of the highest-energy particles--collide with atoms in the soil. When atoms are hit with such energy, neutrons are released, which scatter and collide with other atoms. The atoms get " excited" in the process, and emit gamma rays to release the extra energy so they can return to their normal rest state. Some elements like potassium, uranium, and thorium are naturally radioactive and give
off gamma rays as they decay, but all elements can be excited by collisions with cosmic rays to produce gamma rays. The HEND
and Neutron Spectrometers on GRS directly detect scattered neutrons, and the Gamma Sensor detects the gamma rays.

How GRS Helps Detect Water
By measuring neutrons, it is possible to calculate the abundance of hydrogen on Mars, thus inferring the presence of water.

The neutron detectors are sensitive to concentrations of hydrogen in the upper meter of the surface. Like a virtual shovel "digging into" the surface, the spectrometer allows scientists to peer into this shallow subsurface of Mars and measures the amount of hydrogen that exists there. Since hydogen is most likely present in the form of water ice, the spectrometer is able to measure directly the amount of permanent ground ice and how it changes with the seasons.




I couldn't find anything about this news, and i thought it was worthy to be discussed: thanks to ziggystar60 for kindly bringing this one to my attention.
Internos

nice post internos. you did a good job researching this.
i think we all believe by now that mars had/has water. but i'm wondering, what in earth's name could have happend to mars???
did all the water just dry up? or did mars face the same catastofe as we are about to face?

Thank you, Internos,for an excellent presentation of this scientific findings!

The big "red" planet may actually have looked like this in a very remote past of the universe:


Exploration of Mars suggests that the planet has abundant water ice and may have had oceans in the northern lowlands early in its history. As Mars cooled, the water collected as ice beneath the surface and in the polar ice caps. Liquid Water on Mars, painting by Michael Carroll, reprinted with permission of the artist.
www.lpi.usra.edu...

But what happened to the oceans on Mars? This is from an article published in 2007;

"At some point in the planet's history, a major shift of mass caused the pole to wander about 50 degrees towards its current location and the resulting change in orientation dramatically warped the topography and the ancient shorelines," Professor Mitrovica said.

One critical piece of evidence in support of this hypothesis is the position of the immense Tharsis volcano on Mars - the biggest in the Solar System and some 10,000 times bigger than Mauna Loa, the biggest volcano on Earth. Tharsis is so massive that it will always reorient itself to sit on the planet's equator - it will be spun out to the widest point on the axis of spin, just like a centrifuge. The scientists found that their assessment of how the position of the Martian poles has moved matches precisely the movements of Tharsis as it keeps shifting to maintain its place on the changing position of the equator.

"The chances of this happening randomly are less than 1 in 10,000," Professor Mitrovica said.

As yet the scientists do not understand why the spin axis of Mars moved so much. It may have resulted from a massive deluge of water on the Martian surface resulting in the first Arabia shoreline. The shift in weight caused the planet to tilt on its axis. Once the water disappeared, the pole could have shifted back, then shifted again as a second deluge created the Deuteronilus shoreline. "What we don't know is what caused the poles to shift on Mars and what happened to the water. The ocean may have been gradually converted into water vapour, moved to higher elevations, and flowed beneath the surface. There could be a large mass of water deep within Mars," Dr Perron said.

.......

Water does not make life obligatory, but it does make it far more likely. As yet the only direct evidence for life on Mars has been highly controversial. Ten years ago, Nasa scientists announced that they had found possible signs of life on a Martian meteorite called ALH84001. The potato-sized lump of rock fell to Earth 13,000 years ago and a detailed analysis threw up chemical signatures of life, as well as rod-shaped structures that looked like terrestrial bacteria, but smaller.

Other scientists have been bitterly critical of this analysis, which has gone through a series of claims and counterclaims concerning its authenticity. The only way of truly solving this problem is to look for a similar piece of rock on Mars and bring it back to Earth for analysis. And the best place to find Martian fossils is in sedimentary rock formed by an ocean. At least scientists looking for life on Mars now have a better idea where to find it.

www.independent.co.uk...




[edit on 20/11/08 by ziggystar60]