Lola Gayle, STEAM Register
Mars was bombarded 4 billion years ago by comets and asteroids, and some may have even been as large as West Virginia. According to new research, this bombardment likely enhanced climate conditions enough to make the planet more conducive to life.
If Mars was as barren and cold as it is today, the impacts would have created hydrothermal systems similar to those in Yellowstone National Park, says University of Colorado CU-Boulder Professor Stephen Mojzsis. Those vents in Yellowstone harbor chemically powered microbes, some of which can survive boiling in hot springs or inhabiting water acidic enough to dissolve nails.
Evidence of running water on Mars can be seen in the ancient river valleys, deltas and parts of lake beds. According to Mojzsis, in addition to producing hydrothermal regions in portions of Mars’ fractured and melted crust, a massive impact could have temporarily increased the planet’s atmospheric pressure, periodically heating Mars up enough to “re-start” a dormant water cycle.
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“This study shows the ancient bombardment of Mars by comets and asteroids would have been greatly beneficial to life there, if life was present,” said Mojzsis, a professor in the geological sciences department. “But up to now we have no convincing evidence life ever existed there, so we don’t know if early Mars was a crucible of life or a haven for life.”
Heavy cratering from the Late Heavy Bombardment can still be seen on Mercury, Earth’s moon and Mars. Artist’s impression shows the moon during the Late Heavy Bombardment. Tim Wetherell – Australian National University (CC BY-SA 3.0)
During the Late Heavy Bombardment, our solar system was a shooting gallery of comets, asteroids, moons and planets, reports Jim Scott for CU-Boulder. Unlike Earth, which has been “resurfaced” time and again by erosion and plate tectonics, heavy cratering is still evident on Mercury, Earth’s moon and Mars, Mojzsis said.
Mojzsis and Oleg Abramov, a researcher at the U.S. Geological Survey in Flagstaff, Arizona, created 3D models using a supercomputer to examine temperatures beneath millions of individual craters to assess heating and cooling, as well as the effects of impacts on Mars from different angles and velocities.
Those models showed that the heating of ancient Mars caused by individual asteroid collisions would likely have lasted only a few million years before the Red Planet defaulted to today’s cold and inhospitable conditions.
“None of the models we ran could keep Mars consistently warm over long periods,” said Mojzsis.
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While Mars has spent most of its life in the deep freeze, Earth was most likely habitable over almost its entire existence. Previous research by Mojzsis and Abramov found that the Late Heavy Bombardment period just didn’t have the firepower to extinguish potential early life on Earth. What’s more, the researchers say it may have even given early life a boost if it was present.
“What really saved the day for Earth was its oceans,” Mojzsis said. “In order to wipe out life here, the oceans would have had to have been boiled away. Those extreme conditions in that time period are beyond the realm of scientific possibility.”
So what’s next for the researchers?
“Studies of Mars provide us with valuable information about our own place in the solar system,” he said. “Our next steps are to model similar bombardment on Mercury and Venus to better understand the evolution of the inner solar system and apply that knowledge to studies of planets around other stars.”
Mojzsis will meet with scientists from the California Institute of Technology and NASA’s Jet Propulsion Laboratory in Pasadena next month to discuss possible landing sites and research targets for the upcoming Mars 2020 rover mission. Mars 2020 will carry instruments to seek out past life or present life, hunt for habitable areas and demonstrate technologies for use on future robotic and human missions to Mars.
Results of the Mars study are published in Earth and Planetary Science Letters.
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