Humans have long asked about life on Mars. In 1976 the Viking Lander brought experiments designed to find chemical reactions indicative of life. To scientists' surprise, those reactions were found in abundance. Researchers explained the positive results as chemical reactions, even inventing reactions that had never been observed on Earth. After Viking, Mars was officially called lifeless.
25 years ago this month geologist Robbie Score spent her Christmas holiday Wintering in Antarctica. On December 27, 1984 she was hunting for rocks on the Far Western Icefield near the Allan Hills. She spotted an odd grapefruit-sized rock on the ice. Score immediately identified it as a meteorite, and its greenish colour made it distinct from other meteorites found nearby. Bobbie Score named the rock ALH84001, an Allan Hills meteorite found in 1984. For nine years the odd green rock sat on a shelf unnoticed, but Robbie Score may have stumbled upon one of history's great finds.
An early classification identified ALH84001 as coming from an asteroid. In 1993 geologist Duck Mittlefehldt, a friend of Robbie Score, reexamined the little meteorite and concluded that it had arrived from Mars. Later analysis showed that the rock had first crystallized 4.5 billion years ago, near the dawn of our solar system. 16 million years ago it was launched from Mars by a meteorite impact. After wandering the solar system for millions of years, the green rock landed in Antarctica 13,000 years ago.
The biggest surprise was yet to come. In 1996 colleagues David McKay, Everett Gibson and Kathie Thomas-Keprta discovered signs of bacterial life on ALH84001. They foundd several major bits of evidence, including magnetites and fossil-like forms. Magnetites are used by living organisms to sense direction. After an initial blast of publicity, other researchers found alternate explanations. The debate over life on Mars raged on.
The team's latest paper, Origins of magnetite nanocrystals in Martian meteorite ALH84001,
does a good job of demolishing competing theories. Afer painstaking work, the team shows that alternate explanations of the magnetites are contradictory. This paper will convince many on the fence that life has been discovered from Mars. NASA press release.
The Martian bacteria were thriving at a time when astrophysics says that the Sun was only 75% as bright, and both Earth and Mars were frozen solid. Reality has not cooperated with theory, for evidence says that both planets had temperatures suitable for life. This is the "Faint Young Sun Paradox." Fortunately the Sun turns fuel to energy according to E=mc^2. If the speed of light were changing according to GM=tc^3, solar luminosity would be changed exactly enough to make temperatures comfortable for life.
When evidence is found that c is changing, others are quick to come up with alternate explanations. This is how "dark energy" got started. As with life on Mars, an abundance of evidence will show a changing speed of light.
Labels: mars, meteorites