As NASA’s rovers journey across Mars’s surface and
new satellites orbit the planet, a wealth of information on the red
planet is now available to the public, said astronomer and author
Croswell spoke at this semester’s first installment of
Saturday Morning Physics, a lecture series hosted by the
University’s Physics Department. More than 350 people filled
two auditoriums in the Dennison Building for the talk — a
typical turnout for Saturday Morning Physics, said coordinator and
physics Prof. Timothy McKay.
Croswell presented material from his new book,
“We’ve learned so much about Mars in the last seven
years,” he said. “There are a lot of images available
and a lot of new science. I don’t think you could do a book
like this 10 years ago.”
As if to prove his point, enormous color images of Mars towered
on a screen in front of the audience while he spoke. Some of the
images, including a panorama of the Martian surface and the first
photo of sunset on Mars, were recently taken by NASA’s Mars
Spirit and Mars Opportunity. The two rovers landed on Mars in
Croswell’s talk painted a vivid picture of a planet only
half Earth’s size that nonetheless has much to offer both
scientists and the public.
Mars is particularly fascinating, Croswell said, because it has
preserved its ancient terrain much better than Earth has. Erosion
proceeds slowly on Mars due to the planet’s thin atmosphere,
and Mars also lacks plate tectonics. Plate tectonics — the
motion of large plates of a planet’s crust, past and under
one another — has consumed most of the Earth’s early
terrain, geologists say.
“We really have a chance with Mars to find out the life
history of the planet,” Croswell said. “It’s
preserved so much of the past, but there’s still interesting
things in the present.”
Croswell’s images, which derived from a variety of
sources, showed a scarred Martian surface pockmarked by meteor
impacts throughout its 4.6 billion year lifetime. The more craters
present, the older the region, Croswell said. The planet’s
red color derives from the planet’s high content of iron,
which combines with oxygen to form rust.
One of the most important questions about Mars, Croswell said,
is whether life has ever arisen there. Because life needs liquid
water to survive, NASA’s rovers are currently searching for
evidence that liquid water once existed. “What we’re
really trying to do with these spacecraft is either confirm or
refute our hypothesis that there was once water on Mars,”
He showed features on the Martian landscape that suggest Mars
may once have had liquid, flowing water. These include apparent
riverbeds, flood channels and gullies resembling those created by
water on Earth.
Water may have flowed on Mars as little as a million years ago,
he said, a brief span for a planet whose age is measured in
billions of years.
In a similarly recent timeframe, Mars’ massive volcanoes
— which include Olympus Mons, the solar system’s
largest volcano at more than twice the height of Mt. Everest
— may have erupted less than 20 million years ago.
Croswell is not the first outside speaker at Saturday Morning
Physics, but the lectures are usually given by University faculty
and staff, McKay said. The series organizers felt a talk on Mars
would be timely. “There’s a lot of interest in Mars
right now, what with new rovers landing,” McKay said.
The audience included members of a range of ages, from children
to the elderly. Gerhard Schubert, a teacher at Lakeland High School
in White Lake, said he regularly brings groups of his students to
Saturday Morning Physics.
“This is the second year I’ve been encouraging
students to do this. I don’t mind offering the extra credit
because I view it as an opportunity,” he said.
University alum Lisa Radwick said, “For someone who has a
passing interest in this topic, it was interesting, it was
informative and gave you more than the popular press.”
Her husband Mike Radwick, a member of the University Lowbrow
Astronomers, admitted a keener personal interest in Mars.
“We’re pursuing our intellectual hobby,” he said
of the small knot of Lowbrows who stood discussing the lecture
after its conclusion.
Croswell thinks the public is naturally attracted to Mars.
“I think it’s the life connection, as far as why the
public is interested,” he said.
But Lakeland High School student Mark Morsehead had a different
opinion. Asked what he liked most about Mars, he said,
“It’s gotta be the volcanoes.”