Giant Asteroid Impact May Have Melted Half of Mars's Surface
Mars's dichotomy, or its "two faces," has long been a subject of curiosity for astronomers. Now, scientists from the Swiss Federal Institute of Technology may have shed light on the origins of the phenomenon, painting an extremely violent history of the Red Planet in the process. According to their new study, Mars experienced a giant asteroid collision that melted almost half of the planet's surface, causing the unique appearance we observe today.
The Martian dichotomy is an abrupt shift in the planet's crustal thickness and surface elevation that occurs near the equator. It was first discovered in the 1970's, but astronomers have never been able to determine the cause with any certainty. Previous studies indicated that an asteroid strike near the north pole may have been responsible, but there were still no confirmed answers.
For this study, the researchers used a 3-D simulation of the conditions on Mars 4.5 billions years ago and tested an alternative hypothesis: that an asteroid impact was responsible, but on the other side of the planet. When the enormous simulated asteroid (4,000 kilometers across) hit the planet, sure enough, it caused Mars to develop two distinct zones with distinctly differing crustal thickness and surface elevation, at values that almost exactly matched the observed values on Mars. The simulation also predicted that the massive impact would have caused huge sections of the crust to melt and form an ocean of magma. As the magma ultimately cooled and solidified, it would have caused heightened elevation in certain areas.
A computer simulation does not definitively prove that this is actually the cause of the Martian dichotomy, or that this asteroid strike occurred at all. But it does provide compelling evidence that this is, at the very least, a plausible explanation for the observed physical features of Mars.
"This result has the potential to significantly change our understanding of Mars's past," said study lead author Giovanni Leone. "A rare event may have occurred early in its history that shaped the planet as we see it today."