New geology findings suggest that the generally accepted estimates for the age of the Martian surfaces -- which influence theories about its history and whether or not it once sustained life -- could be way off. The research eventually might 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 the University of Buffalo 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.
|Tyrrhena Patera Volcano Spillage Image Credit: NASA/JPL/Malin Space Systems
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, Mars (click for larger image) Image Credit: NASA/JPL/Malin Space Systems
"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."