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The search for water ice on Mars
December 2003 - May 2004
Latest: NASA's Opportunity rover has demonstrated some rocks on Mars probably formed as deposits at the bottom of a body of gently flowing saltwater.
Prospecting in 2003 by NASAs
Mars
Odyssey spacecraft has shown that there is a vast
amount of hydrogen below the surface of
Mars. From about 55 degrees latitude to the poles,
Mars boasts extensive deposits of soils that are rich in water-ice, bearing an
average of 50% water by mass (source: Los Alamos' neutron
spectrometer on Odyssey).
Ref: Mitrofanov et al., Carbon Dioxide Snow Depth and Subsurface
Water-Ice Abundance in the Northern Hemisphere of Mars,
Science 2003 300: 2081-2084.
Mars is a cold and dry planet, with both dust clouds and ice clouds in the atmosphere, but the subliming polar caps are probably composed of water ice and carbon dioxide ice. However, NASA scientists have said if any water ice existing on Mars were somehow warmed, it still wouldn't melt into water. The thin Martian atmosphere instead would cause the ice to sublime directly into water vapour. The atmosphere is composed of carbon dioxide (95%), molecular nitrogen (2.7%), argon (1.6%), molecular oxygen (0.13%), carbon monoxide (0.07%), plus traces of water vapour.
It is thought that there was abundant liquid water at various times in Mars' history.
The strategy for NASA's latest stage of Mars
exploration is
based on sending the twin robotic Rovers, Spirit and
Opportunity,
to two spots on the red planet where the probability of finding water is
highest.
Spirit landed on 4 January 2004 in the heart of Gusev Crater, a massive basin that was carved out by the impact of an asteroid or comet early in Mars' history, and is thought to have once held a gigantic lake. A long, deep valley apparently chiselled by ancient flows of water leads into the cratar, suggesting the lake was fed by an ancient river.
On 24 January 2004, Opportunity has landed on the so-called Meridiani Planum, a smooth plain near Mars' equator where NASA's orbiting Mars Global Surveyor has detected an abundance of grey haematite, a mineral that on Earth usually forms in association with liquid water. Some environmental conditions that can produce haematite, such as a lake or hot springs, could be hospitable to life.
The main task for both rovers in coming weeks and months is to explore the areas around their landing sites for evidence in rocks and soils about whether those areas ever had environments that were watery and possibly suitable for sustaining life.
These are two of the three unmanned Mars expeditions launched last summer to take advantage of the unusually close proximity (35 million miles) of Mars and Earth. The joint European Mars exploratory vehicle Beagle 2, named after the ship that carried Charles Darwin on his voyage of discovery in the 1830s, touched down on the Martian surface near the equator on Christmas Day 2003, but as yet has failed to communicate with Earth.
The amount of frozen water near the surface in some relatively warm
low-latitude regions on both sides of Mars' equator appears too great to
be in equilibrium with the atmosphere under current climatic conditions,
said Dr. William Feldman of the US Los Alamos National Laboratory. He is
the lead scientist for an Odyssey instrument that assesses water content
indirectly through measurements of neutron emissions.
>> Further information.
Notes
References on the SPRILIB database on Mars to 2003, compiled by bibliographers in the SPRI Library.
It is possible that primitive life forms may now be present beneath the polar ice caps or in subterranean springs warmed by heat vents around smouldering volcanoes. There could also be Martian equivalents of lithotrophs, single-celled plants that have been seen in Antarctica. If life is found there it won't be little green men, but very tiny microorganisms.
Recent studies of the planet show evidence that expanses of water ice were located not only at Mars’ poles, but also at its central latitudes. The presence of this mid-latitude ice is explained by scientists as related to extreme changes in the tilt of the Martian axis by as much as 20 degrees. It is believed that there could have been as many as 50 such obliquity variations over the last 5 million years, a relatively short period of time.
The surface temperature on Mars is much lower than on the Earth: it reaches approximately 0°C in summer, but the average daily temperature is about -50°C. Polar winter temperatures can be as low as -120° C. The ground on Mars is permanently frozen to a depth of approximately 1 km.
The only other place in the solar system where water is believed to exist is Europa, a moon of Jupiter, where a liquid ocean may lie beneath an icy crust.
Patrick Moore on Mars:
It's more like the Earth than any other body. There could be a certain
amount of life there and it's very important to find out. Microscopic
stuff, nothing as advanced as a spider. We can't be sure of life
elsewhere at the moment, we've got no proof.
Links
NASA Mars Exploration Rover Mission - or use their alternative website.
NASA Mars Program and NASA Homepage
ESA
Beagle 2
- universities
involved in the mission
PPARC Mars Express and
Beagle 2
Mars atmosphere modelling and observations, a workshop held on 13-15 January 2003, Granada, Spain
Webpage on Mars from the Institute of Astronomy, University of Cambridge, UK.
Compiled from web sources.