In 1996, a team of NASA researchers stunned the world when they announced that
they had found fossil
evidence of life inside Mars meteorite ALH
84001, a chunk of rock that had been knocked
off Mars and had landed on Earth. Five years later, the scientific controversy
over ALH 84001 continues unabated. The NASA team has proposed several
lines of evidence, including the presence of tiny magnetic crystals known
as magnetites.
While some magnetites form inorganically, others are created
by bacteria. NASA researcher Kathie
Thomas-Keprta has claimed that the distinctive shape of magnetites found in
ALH 84001 could
only have been produced by bacteria. Now scientists Peter
Buseck and Martha McCartney of Arizona State University argue that the NASA
team's method for determining the three-dimensional structure of the microscopic
crystals was inaccurate. They contend that their improved technology reveals that
the shape of bacterial crystals does not match that of the ALH 84001 crystals
nearly as closely as the NASA team suggests. In a strongly worded rebuttal
to Buseck and McCartney, the NASA researchers respond that Buseck and McCartney's
technique for determining shape is not new, and in any event should produce results
equivalent to their own. They also point out that Buseck and McCartney used magnetites
from a different strain of bacteria, which, they suggest, could account for the
differences in the shapes that each team found.
Oct 17, 2002 | SCIENCE
Looking for Carbonates in Dry Places
(Astrobiology Magazine) - A recent discovery may challenge the idea that carbonates could be a sign of past water on other planets.
Aug 14, 2002 | SCIENCE
Continuing Search for Ancient Martian Life
(Astrobiology Magazine) - Researchers have published their latest evidence for ancient microbes in a meteorite from Mars.
May 20, 2002 | SCIENCE
Mars Meteorite's Link to Life Questioned
(Space.com) - A pair of scientists argue that magnetite crystals in a Mars meteorite weren't produced by microorganisms.
Mar 20, 2002 | SCIENCE
No Knockouts in Martian Meteorite Showdown
(Sky and Telescope) - Two teams of scientists argue that magnetite crystals in a Mars meteorite are not necessarily evidence of life.
Jan 07, 2002 | SCIENCE, MISSIONS, TECHNOLOGIES
Signs of Life: On the Lookout for Extraterrestrial Sweet Spots
(Space.com) - A new report reviews methods for detecting extraterrestrial life, and for preventing cross-contamination of planets.
Aug 29, 2001 | SCIENCE
From Mars to Earth in a Meteorite?
(Scientific American) - A study suggests that the interior of a meteorite from Mars remained cool enough to transport life to Earth.
Jul 11, 2001 | SCIENCE
How Small Can Life Be?
(NASA Astrobiology Institute) - As advanced microscopes enable us to peer deeper into the realms of inner space, biologists have been faced with a vexing question: Is there a size limit on life?
Jul 10, 2001 | SCIENCE
The Meaning of Life
(NASA Astrobiology Institute) - Researchers consider the societal implications of finding life elsewhere in the universe.
Jun 19, 2001 | SCIENCE
Mars Meteorite Discovered in Oman Desert
(CNN) - The meteorite, known as SAU 094, could help determine if life ever existed on Mars.
Apr 30, 2001 | SCIENCE
Does the Famous Martian Meteorite Really Point to Life?
(NASA/Space.com) - Debate continues over whether Martian meteorite ALH84001 contains evidence of ancient life on Mars.
Feb 26, 2001 | SCIENCE
New evidence of ancient life on Mars
(NASA Astrobiology Institute) - New evidence from a Martian meteorite strengthens the case that microorganisms once existed on Mars.
Dec 13, 2000 | SCIENCE
New report offers evidence of primitive life on Mars
(NASA) - Tiny magnetite crystals, identical to those used by bacteria on Earth, have been found in the Martian meteorite ALH84001.
Mar 01, 2000 | SCIENCE
Sulfur in meteorites offers no evidence of Mars life
(SpaceViews) - Scientists claim that that sulfur concentrations found in Martian meteorites are the result of atmospheric processes and not of life on Mars. Sulfur concentrations may not be an effective biomarker.
