Madrid, 16 (European Press)
A new model suggests that large, high-velocity impacts during Venus’ early history could explain the differences between Venus and its rocky brother Earth.
The two planets are similar in many ways. They have similar sizes, masses, and densities, and are at relatively similar distances from the Sun. However, some key differences, such as habitability, atmosphere composition and plate tectonics, remain unexplained.
High-speed impacts could help explain why Earth is habitable while Venus isn’t, according to new research presented at the fall meeting of the AGU (American Geophysical Union).
“In the beginning, at the beginning of the solar system, the shocks were huge,” Simon Marchi, a planetary scientist at the Southwest Research Institute, said in a statement. “If one of the early collisions was larger than, say, a few hundred kilometers in diameter, it could have affected the depth of the planet’s interior, along with its surface and atmosphere. These massive collisions will affect basically everything about the planet.”
Recent work by a different research group has shown that collisions during the late Venus accretion phase, about 4.5 to 4 billion years ago, could have hit the planet at speeds much higher, on average, than those hitting Earth. More than a quarter of collisions with Venus would have occurred at speeds of at least 30 kilometers per second.
The new research shows that large, high-velocity impacts on Venus cause twice as much mantle melting as the melt caused by the impact on Earth. According to the new research, a high-speed collision with Venus at a shallow angle would have caused the entire mantle to melt.
According to Markey, when one of these massive high-speed collisions hits Venus, it will fundamentally disrupt and reset the planet’s evolution. Venus can go from a solid, rocky body to a molten chaos in moments, altering the minerals and physical structure of the planet’s interior and surface. Any pre-existing atmosphere would have been largely destroyed and replaced by volatile gases arising from the melt. A single high-velocity impact would eventually have determined whether or not plate tectonics formed, an important aspect of habitability.
While it is likely that large impacts have affected both Earth and Venus, the latter may have suffered a greater degree of dissolution and disruption due to the high speed of their impacts, placing the planets on divergent evolutionary paths. For both the planets and the solar system as a whole, these early collisions had dire consequences for their habitability – or lack thereof – today.
“These collisions were responsible for shaping the solar system,” Markey said. “It’s not a fantasy to say that without these processes, we would be living in a completely different environment and probably wouldn’t be here.” “We need to ask ourselves to what extent these early violent events were shaped by the planet we live on today.”