Mars- Water of  Life?

After landing on Mars on July 4th of this year, the Mars Pathfinder (named the Sagan Memorial Station) returned an incredible 1.2 gigabits of data, which included 9669 lander and 384 rover images and about 4 million temperature, pressure, and wind measurements. Newly published studies based on the chemical analyses returned by Pathfinder indicate that some rocks on the red planet may be high in silica, implying differentiated parent materials. This, along with the presence of rounded pebbles and cobbles and a possible conglomerate, suggest fluvial processes that imply liquid water in equilibrium with the atmosphere.

Caption: Science publishes the first peer-reviewed data from the Pathfinder mission to Mars. Image processed at Jet Propulsion Laboratory, Pasadena, CA

"Taken together, the data compiled so far from Pathfinder all appear to be consistent with a water-rich planet that may be more Earth-like than previously recognized," say JPL researchers, "with a warmer and wetter past in which liquid water was stable and the atmosphere was thicker."

Doppler and range data gathered by Pathfinder's radio communications system to determine the rate of rotation of the Red Planet and the wobble in the axis of rotation also suggest a more Earth-like planet than previously suspected. These  data indicate that Mars has an iron-rich core of about 1,300 to 2,000 kilometers in radius that is much denser than the surrounding mantle- similar to Earth's interior. Further analyses allowed the researchers to determine the likely Martian climate over the past millions of years. They report that the evidence is "in good agreement" with a model in which a mass amount of carbon dioxide shifts seasonally between the atmosphere and the planet's polar ice caps.

The Pathfinder landed in what appeared to be a huge, dry flood plain. The Sojourner rover was able to provide a detailed geologic report from the site. The rover dug up samples for examination and estimated the mechanical properties of the deposits. The rover reported the presence of numerous well-rounded pebbles that may be sedimentary--indicative of wind, water or a glacier--rather than volcanic in origin. Surface pebbles may have been rounded by flood waters at the site, or liberated from larger sedimentary rocks (called conglomerates) by weathering.

"The possible discovery of a conglomerate on the martian surface is intriguing and would require some rethinking of the weathering processes on Mars. Conglomerates imply that water existed elsewhere and earlier than the suspected flood that carved out the valley in which Pathfinder landed," the researchers note.

MARTIAN METEORITE CONTAINS NO BIOLOGICAL LIFE, RESEARCH TEAM SAYS

Meanwhile, another team of researchers reporting in Nature concludes it analysis of the famous Martian meteorite, ALH84001, with the claim that the rock contains no biological life forms.

ALH84001 is a small meteorite that landed on Antarctica some 15 million years ago. Last year, a team of researchers at NASA's Johnson Space Center claimed to have identified organic compounds on the Martian meteorite, the first ever such discovery. The controversy has swung back and forth ever since.

In the latest study, a team of researchers from Case Western Reserve University, the Georgia Institute of Technology and the University of Tennessee duplicated the methods of a NASA team, but reached far different conclusions. The team reports that most of the purported nanofossils or "worm-like images" are nothing more than lamellae, or fractured surfaces of pyroxene and carbonate crystals.

In the first study, which used transmission electron microscope imagining (TEM), the researchers found non-biological magnetite whiskers on or near the surfaces of the carbonates. Superficially the whiskers look like worms, but in fact they have nothing to do with biological processes, according to Ralph Harvey, senior research associate in the Department of Geological Sciences, Case Western University. Harvey headed the team that  found the meteorite in the 1984.

The latest study took place over the past six months as the researchers re-examined the meteorite using the new techniques. This time they found yet another population of worm-like forms that are actually mineral lamellae formed by non-biological, geological processes. The lamellae look like worms or nanofossils, but when the specimen is tilted and viewed from another angle, it clearly shows that the lamellae are attached and part of the mineral surfaces.

"Peculiar surface structures or segmentation on the worm-like forms are artifacts from conductive metal coatings applied to the samples for imaging in the electron microscope. This is not the first time metal coating artifacts have lead to misidentification of nanofossils in rocks,"  said John Bradley, of the School of Material Science and Engineering at Georgia Institute of Technology.

"We have now found two different types of mineral forms in ALH84001 that look just like nanofossils, but they are strictly non-biological origins. Sometimes even nature has a perverse sense of humor," he added.

This latest study is not likely to end the debate. In a rare counterpoint article, the original NASA team responds to the group's findings, disagreeing with its conclusions. They claim to have identified different structures than those reported in the newer analysis.

The Pathfinder data appears in a series of articles in the Dec.5, 1997 issue of Science. The meteorite research appears in the Dec. 4, 1997 issue of Nature.