http://www.pasadenastarnews.com/Stories/0,1413,206~22097~1496809,00.html Meteorite helps Caltech student prove his thesis
Rocky road to success By Becky Oskin Pasadena Star News July 6, 2003 PASADENA -- Six years ago, Ben Weiss spent all night slicing the oldest rock on Earth into pieces the size of a child's fingernail. The precious slivers of dark brown meteorite offered Weiss, then a first-year Caltech graduate student, a chance to delve into the most hotly contested debate in geology: whether a potato-size piece of Mars blasted from the red planet 15 million years ago carried remnants of Martian life to Earth. "All night long we kept laughing out of excitement and disbelief as we played with not only an invaluable rock from Mars but the oldest known rock from any planet!' Weiss, 29, wrote in his thesis. >From those bits of 4-billion- year-old Mars rock, Weiss proved the meteorite took a cool trip to Earth, never reaching sterilizing temperatures that could kill life forms hitching a ride. He also found evidence Mars had a magnetic field protecting a thick atmosphere in its early history conditions conducive for evolution of the simplest microbes. For these discoveries, this year Caltech awarded Weiss its highest honor for graduates, the Clauser prize. Given annually to a doctoral student whose research exhibits potential for opening up new avenues of human thought and endeavor, as well as by the ingenuity with which it has been carried out, the award validated Weiss' choice to follow his love of a science he says was even more crackpot six years ago than it is today. "The field I'm in is definitely not a traditional kind of science. It's a historical science. It's hard to really prove something. You have to be careful not to drown in speculation and stick to the facts,' Weiss said. Weiss originally set out to study the planets as an astronomer, earning a physics degree from Amherst University in Massachusetts, not too far from his home in upstate New York. After a stint as an exchange student in Singapore, he enrolled at Harvard University as a graduate student interested in cosmological lensing, the deflection of light by gravity. That was also the year Pathfinder arrived at Mars and captured the public's interest with stunning pictures of the planet's surface. Mars science and its connection to life on Earth found a captive audience in Weiss, and he transferred to Caltech to work with geobiologist Joe Kirschvink, who had samples of the Martian meteorite ALH84001. It was a risky decision, Weiss said. "It could have been a disaster' if nothing interesting came of his investigations, leaving him without a thesis. Instead, Weiss ended up with what Kirschvink calls a slam dunk win proof that Mars could have hosted life and perhaps even seeded Earth. "Ben's thesis work has doubled the problem of the origin of life,' Kirschvink said. The proof that fractured rock ALH84001 could have transported simple Martian life forms to Earth comes from many different areas of geology, but Weiss focused on magnetization. Kirschvink's lab specializes in paleomagnetism, the remnant alignment of iron grains within a rock. Weiss figured out a way to apply the most sensitive magnetic field detector in the world to examine the meteorite and query its history. One of his first results showed that grains of the iron-bearing mineral magnetite, hidden with carbonates stuck in fractures criss-crossing the meteorite, were aligned magnetically when the rock was heated to about 100 degrees Fahrenheit. The results meant that even when ALH84001 was blasted off Mars and burned its way through Earth's atmosphere, those magnetite grains were never exposed to temperatures warmer than the average summer day in Southern California. And if one rock can travel to Earth at temperatures hospitable to life, maybe some of the billions of tons of rocks kicked off the surface of Mars over the eons could have brought Martian life here. Weiss and Kirschvink call it panspermia: we could all be descended from Martians. It's worth noting that a standing joke among Weiss' Caltech colleagues is that he's a Martian who has invaded a human body. "He's just off the wall, or maybe he's just an absent-minded professor,' Kirschvink said. The panspermia theory is what some scientists call crackpot, but Weiss' other results from the Martian meteorite have revolutionized understanding of the planet's early history. Stripping away the meteorite's magnetization revealed Mars once had a planetary magnetic field. Mars does not have a field today. "The magnetic field has really important implications for Mars' core, and also may be tied to the evolution of the Martian climate,' Weiss said. Gas trapped in the meteorite's minerals does not match the ratio of gases of Mar's modern, thin atmosphere. Younger Martian meteorites do match. The implication: "We have a sample of 4-billion-year-old Martian atmosphere,' Weiss said. If Mars once had a magnetic field like Earth, it would protect the planet's atmosphere from bleeding off into space. But if the magnetic field turned off when the interior of Mars cooled, ending the rotation that produced the field, then the decline of the magnetic field might be linked to Mars' vanished atmosphere. This transition seemed to happen about 4 billion years ago, when ALH84001 was fractured on Mars during a heavy bombardment of meteorites. Earth's moon also was pounded by space rocks during the period, hinting at some systemwide cataclysm. "This rock was severely busted up 4 billion years ago,' Weiss said. "The first half-billion years was a really violent time on Mars, and this rock records that,' he said. Now that Weiss has graduated from Caltech, he appears ready to leave Mars behind. His future plans include trying to figure out when Earth's magnetic field first turned on, and analyzing interplanetary dust particles to learn more about the earliest magnetic fields in the solar system. MIT will build Weiss, who has accepted a professorship there, one of the most sensitive magnetometers ever. "It's so sensitive that anything I think of to study will be interesting,' Weiss said. Becky Oskin can be reached at (626) 578-6300, Ext. 4451, or by e-mail at [EMAIL PROTECTED] ______________________________________________ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
