BUFFALO, N.Y. -- Research by a University at Buffalo planetary
geologist suggests that generally accepted estimates about the
geologic age of surfaces on Mars -- which influence theories about
its history and whether or not it once sustained life -- could be
Funded by the National Aeronautics and Space Administration, the
research eventually could overturn principles about the relative
ages of different areas on the Red Planet that have not been
questioned for nearly 20 years.
The findings also could cause scientists to reconsider the use
of a critical tool -- counting impact craters created by
meterorites -- that geologists use to estimate the age of planets
they cannot visit in person.
"This has the potential to change everything we thought we knew
about the age of different surfaces on Mars," said Tracy Gregg,
Ph.D., assistant professor of geology at UB and chair of the
Planetary Geology Division of the Geological Society of America.
David Crown, Ph.D., of the Planetary Science Institute, is Gregg's
co-investigator on the grant.
Gregg's research concerns an area on Mars called Hesperia
Planum, which has been used since the 1980s to define the Hesperian
epoch, the second of the planet's three geologic time periods.
But in the past several years, recent analyses of images
obtained from the Mars Orbiter Laser Altimeter, (MOLA), the Mars
Orbiter Camera (MOC) and other instruments have led to new
estimates for the duration of the Hesperian epoch, ranging from
just 300,000 years to 1-2 billion years, Gregg explained.
While other planetary geologists now are attempting to reconcile
these two models, she said, her focus is on trying to figure out
which surfaces on Mars originated in the Hesperian epoch, research
that, in turn, probably will help to further define the duration of
the Hesperian epoch.
"For almost 20 years, Hesperia Planum has served as the basic
time marker on Mars," said Gregg.
"When we want to identify how old rocks are without the benefit
of samples, we count impact craters, the big holes in planetary
surfaces that are made by meteorites that crash into them,"
explained Gregg. "The more impact craters there are on a surface,
the older it is."
But during the course of Gregg's research reviewing images of
Tyrrhena Patera, a volcano located in the middle of Hesperia
Planum, she began finding deposits from not one Martian geologic
epoch but from several.
Gregg made her findings using images obtained from the Viking
Orbiter, the Mars Global Surveyor, the MOLA and the MOC. She also
will be using data NASA is making available from THEMIS, the
Thermal Mapping Infrared Spectrometer, which measures surface
temperatures on Mars.
"Hesperia Planum is not one age. Its surface actually is a
combination of materials that are very old, materials that are very
young and some that are in between," she said, "and the volcanoes
there are the reason why."
Gregg recently has demonstrated that two volcanoes in western
Hesperia Planum were active during a much longer period than
previously was understood and that the products of the eruptions
traveled much further, signaling a greater intensity of volcanic
activity than originally was thought.
Her findings, she said, are similar to ones made about 20 years
ago on Earth, when geologists discovered that Yellowstone National
Park in Wyoming was the center crater of an enormous volcano and
that its deposits stretched as far as the state of Illinois.
Those findings, she said, changed fundamentally the
understanding of volcanic activity on Earth.
In a similar vein, she said, the new observations about the
great distances traveled by deposits of Martian volcanoes and their
influence on the age of surfaces may cause a similar
reconsideration of understanding of the history of Mars.
"I think that we are about to discover that Hesperia Planum,
this surface that has acted as a basic time marker for Mars, has a
very different age than we thought," she said. "If it turns out
it's much older than we thought, then it means that the system shut
down a lot earlier and the chances of finding active living
organisms on Mars are much slimmer.
"If, on the other hand, it turns out to be much younger, then
it means Mars still may be volcanologically active, and if it is,
that increases the possibility of extant life on Mars."