If the atmosphere of Venus was at any point thin and similar to Earth’s, then ancient asteroid impacts transferred potentially detectable amounts of Venusian surface material to the Moon, according to new research from Yale University. Recovery and isotopic analyses of Venusian surface samples from the lunar surface would determine with high confidence both whether and when Venus harbored liquid oceans and/or a lower-mass atmosphere.
Meteoroids bombarded the Earth-Moon system 800 million years ago. Image credit: Murayama, Osaka University.
“Asteroids and comets slamming into Venus may have dislodged as many as 10 billion rocks and sent them into an orbit that intersected with Earth and Earth’s Moon,” said Yale University researchers Samuel Cabot and Gregory Laughlin.
“Some of these rocks will eventually land on the Moon as Venusian meteorites,” Cabot added.
“Catastrophic impacts such as these only happen every hundred million years or so — and occurred more frequently billions of years ago.”
“The Moon offers safe keeping for these ancient rocks. Anything from Venus that landed on Earth is probably buried very deep, due to geological activity. These rocks would be much better preserved on the Moon.”
Many scientists believe that Venus might have had an Earth-like atmosphere as recently as 700 million years ago.
After that, the planet experienced a runaway greenhouse effect and developed its current climate.
“The Venusian atmosphere is so thick today that no rocks could possibly escape after an impact with an asteroid or comet,” Cabot said.
The scientists cited two factors supporting their theory:
(i) asteroids hitting Venus are usually going faster than those that hit Earth, launching even more material;
(ii) a huge fraction of the ejected material from Venus would have come close to Earth and the Moon.
“There is a commensurability between the orbits of Venus and Earth that provides a ready route for rocks blasted off Venus to travel to Earth’s vicinity,” Professor Laughlin said.
“The Moon’s gravity then aids in sweeping up some of these Venusian arrivals.”
There are several standard chemical analyses that can pinpoint the origin of moon rocks, including any that came from Venus.
Different ratios of specific elements and isotopes offer a kind of fingerprint for each planet in the Solar System.
“An ancient fragment of Venus would contain a wealth of information,” Professor Laughlin said.
“Venus’ history is closely tied to important topics in planetary science, including the past influx of asteroids and comets, atmospheric histories of the inner planets, and the abundance of liquid water.”
The team’s paper will be published in the Planetary Science Journal.
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Samuel H.C. Cabot & Gregory Laughlin. 2020. Lunar Exploration as a Probe of Ancient Venus. PSJ, in press; arXiv: 2010.02215
