STUDY BY TWO YALE UNIVERSITY RESEARCHERS SUGGEST - LUNAR SURFACE MAY CONTAIN ROCKS FROM VENUS

A comet strikes ancient Venus. (Illustration by Sam Cabot)

A study by two researchers from Yale University published in arXiv suggest that traceable amount of Venusian rock could be found on Lunar surface. They have showed in their paper that if the atmosphere of the Venus was at any point thin and similar to Earth’s atmosphere, then traceable amount of rock from Venus surface could have transferred to the Moon by some ancient asteroid impacts. Moon does not have any atmosphere and lacks any significant geological activity. So, its highly possible that the samples from the Venusian surface could have persisted on Lunar surface. By analysing the rocks its likely possible to learn the history of Venus, it can reveal the past existence of any oceans.

Venus experiences much higher flux of asteroid impact compared to Earth, due to these impacts materials from surface of Venus could be ejected. Their analytical models and simulations show that more than 0.7% of the ejected rocks from Venus could have landed on Lunar surface. Their study indicate that the Venusian rock concentration would be 0.2 ppm on Lunar regolith, if water on Venus was lost in last 3.5 Gyr. On the other hand, if the water on Venus was lost 4 Gyr ago then the concentration of Venusian material would be 0.3 ppm. So, by recovering the Venusian surface sample and analysing them, we can determine when Venus lost its liquid oceans or whether Venus ever had any liquid oceans.

Schematic of a vertical impact at the surface of a terrestrial body. This example depicts the resulting processes from a 10 km s−1 projectile, including: spallation of near-surface material, which may reach the escape velocity; the interference zone which reduces the maximum pressure (Pmax) experienced by the rock; ejection of a vapor plume; rock undergoing plastic deformation at pressures exceeding the Hugoniot Elastic Limit (HEL); melting in the immediate vicinity of the impact; and Grady-Kipp fragmentation of rock deeper into the target. At large depths, rock fragments into bigger pieces due to reduced maximum pressure. Excavation flows clear out the region which becomes the crater. The contours of constant pressure are hemispherical below the impact, but sharply turn inwards at the interference zone. The x-axis corresponds to horizontal distance from the impact site. Adapted from (Melosh 1984).

According to the researchers analysing the existing Lunar samples from Apollo missions or samples from any upcoming Lunar missions could provide us an answer.

Samuel Cabot, one of the authors of the paper said, "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. Some of these rocks will eventually land on the Moon as Venusian meteorites.”

“Catastrophic impacts such as these only happen every hundred million years or so — and occurred more frequently billions of years ago,” Cabot further added.

“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.”

Cabot further said, “The Venusian atmosphere is so thick today that no rocks could possibly escape after an impact with an asteroid or comet”.

According to Prof. Laughlin, “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. The Moon’s gravity then aids in sweeping up some of these Venusian arrivals”.

“An ancient fragment of Venus would contain a wealth of information,” said Prof. Laughlin

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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