Variety

Ocean once covered part of Red Planet

Mars Express Radar yields strong evidence:

European Space Agency’s (ESP’s) Mars Express has returned strong evidence for an ocean once covering part of Mars. Using radar, it has detected sediments reminiscent of an ocean floor within the boundaries of previously identified, ancient shorelines on Mars.

The MARSIS radar was deployed in 2005 and has been collecting data ever since. Jeremie Mouginot, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) and the University of California, Irvine, and colleagues have analysed more than two years of data and found that the northern plains are covered in low-density material.

“We interpret these as sedimentary deposits, maybe ice-rich,” says Dr Mouginot. “It is a strong new indication that there was once an ocean here.”

The existence of oceans on ancient Mars has been suspected before and features reminiscent of shorelines have been tentatively identified in images from various spacecraft. But it remains a controversial issue.

Two oceans have been proposed: 4 billion years ago, when warmer conditions prevailed, and also 3 billion years ago when subsurface ice melted, possibly as a result of enhanced geothermal activity, creating outflow channels that drained the water into areas of low elevation.

“MARSIS penetrates deep into the ground, revealing the first 60-80 metres of the planet’s subsurface,” says Wlodek Kofman, leader of the radar team at IPAG.

“Throughout all of this depth, we see the evidence for sedimentary material and ice.”

The sediments revealed by MARSIS are areas of low radar reflectivity. Such sediments are typically low-density granular materials that have been eroded away by water and carried to their final destination.

This later ocean would however have been temporary. Within a million years or less, Dr Mouginot estimates, the water would have either frozen back in place and been preserved underground again, or turned into vapour and lifted gradually into the atmosphere.

“I don’t think it could have stayed as an ocean long enough for life to form.”

In order to find evidence of life, astrobiologists will have to look even further back in Mars’ history when liquid water existed for much longer periods.

Nevertheless, this work provides some of the best evidence yet that there were once large bodies of liquid water on Mars and is further proof of the role of liquid water in the martian geological history.

“Previous Mars Express results about water on Mars came from the study of images and mineralogical data, as well as atmospheric measurements.

Now we have the view from the subsurface radar,” says Olivier Witasse, ESA’s Mars Express Project Scientist.

What is Mars Express?

The European Space Agency (ESA) and its member countries began talking about a mission to Mars ever since the Russian Mars ‘96 mission failed.

That spacecraft carried several European instruments, and the loss to European planetary science was devastating. Mars Express was conceived as a low-cost way to refly those experiments and also carry a lander communications relay which would support missions from 2003 onward. Mars Express successfully entered orbit of Mars on December 25, 2003.

It has performed excellently since then, and is in the process of carrying out its primary mission.

In early 2004, the science team for Mars Express confirmed that the spacecraft had detected evidence of water ice all throughout the southern polar cap. Mars Express has also returned a stream of tantalising images of Vallis Marineris, and other planetary features of Mars.

For surface study, Mars Express carries four instruments. A High Resolution Stereo Camera (HRSC) will make possible topographic maps of Mars and can capture images up to a 12 metre resolution.

An IR Mapping Spectrometer (aka OMEGA) conducts rock and soil analyses in the infrared spectrum.

A Radio Science Experiment (RSE) measures Mars’s interior composition and geodesy. A Sub-surface Sounding Radar / Altimeter (SSRA) is measuring the depth and composition of the Martian regolith.

To study the atmosphere, Mars Express carries three instruments. An Energetic Neutral Atoms Analyser (or ASPERA) studies the upper atmosphere and examines the effects of the solar wind on it.

A Planetary Fourier Spectrometer (PFS) studies the atmosphere in infra-red, enabling 3D charts of temperature and pressure to be produced. A UV Atmospheric Spectrometer (aka SPICAM) measures the atmospheric composition and structure.

Mars Express will likely produce many more discoveries during its mission.

[Facts of planet]

* Known since prehistoric times, Mars is still a favorite of choice for human exploration.

*Mars is the fourth planet from the Sun and the seventh largest.It is named for the Roman g od of War,

*It is sometimes referred to as the Red Planet.

*The density of Mars is about 30 per cent less than that of Earth (3.94 g/cm3 vs. 5.52 g/cm3). Its core is probably similar to Earth’s, mostly iron, with small amounts of nickel, but spacecraft mapping of its gravity field seem to indicate that its iron-rich core and mantle are a smaller portion of its volume than on Earth.

*Mars’ atmosphere is 95 per cent carbon dioxide, nearly 3 per cent nitrogen, and * nearly 2per cent argon with trace quantities of oxygen, carbon monoxide, water vapor, ozone, and other trace gases.

The first spacecraft to visit Mars was Mariner 4 in 1965. Several others followed including Mars 2, the first spacecraft to land on Mars and the two Viking landers in 1976. Ending a long 20 year hiatus, Mars Pathfinder landed successfully on Mars on 1997 July 4. In 2004 the Mars Expedition Rovers “Spirit” and “Opportunity” landed on Mars sending back geologic data and many pictures; they are still operating after more than three years on Mars. In 2008, Phoenix landed in the northern plains to search for water.

*Three Mars orbiters (Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Express) are also currently in operation.

Courtesy: The Independent