[meteorite-list] Mars Meteorite Helps Caltech Student Prove His Thesis

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:20:59 2004
Message-ID: <200307061857.LAA11145_at_zagami.jpl.nasa.gov>

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
becky.oskin_at_sgvn.com.
Received on Sun 06 Jul 2003 02:57:28 PM PDT