Ancient fragments of Venus on the Moon “will certainly be interesting once we find them, especially since the surface of Venus is so hard to study with landed vehicles, due to the high temperature and pressure,” Fred Taylor, Halley Professor of Physics Emeritus at the University of Oxford told The Daily Galaxy about 2019 research by Yale astronomers that suggests that our Moon may harbor clues that Venus may have had an Earth-like environment with water and a thin atmosphere billions of years ago. Their findings follow recent studies suggesting that our sister planet may have been the solar system’s first habitable planet.
Scientists conjecture that Venus may have resembled Earth for its first three billion years, with vast oceans and possibly even microorganisms. Astronomers have speculated that strange dark patches, i.e. “unknown absorbers”, that have been recently detected floating inside the clouds of Venus may prove to be extraterrestrial microorganisms that capture large amounts of solar radiation. The tentative microorganisms exist in Venus’ upper atmosphere –the most Earth-like location in the solar system, roughly equivalent to the air pressure at the summit of Mount Kilimanjaro.
“Venus has had plenty of time to evolve life on its own,” said Sanjay Limaye at the University of Wisconsin Space Science and Engineering Center, noting that “some models suggest Venus once had a habitable climate with liquid water on its surface for as long as 2 billion years. “That’s much longer than is believed to have occurred on Mars.”
10 Billion Rock Fragments Over the Eons
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,” said Cabot, lead author of the study. Cabot observes that catastrophic impacts such as these only happen every hundred million years or so — and occurred more frequently billions of years ago.
There is direct evidence that some meteorites that have fallen to Earth originated from Earth’s other neighboring planet, Mars. Thousands of meteorites have been found in Antarctica due to their contrast with the white pristine background. At least 100 of these meteorites have chemical compositions matching the Martian landscape, suggesting some asteroid hit Mars in the distant past that ejected Martian debris into the inner Solar System. It is highly likely that something similar happened to Venus, sending Venusian rocks on long-term trajectories intersecting the Earth and the Moon.
A similar phenomenon may have occurred on Earth 66 million years ago when an asteroid hit Earth with an impact equivalent to 100 billion Hiroshima bombs. This Chicxulub impact at the Yucatan Peninsula released the equivalent of 100 million megatons of TNT, creating a 20-mile deep, 110-mile wide hole, sterilizing the remaining 170 million square miles and killing the majority of species on Earth. It was comparable to an impossible magnitude 12 earthquake–enough force enough to lift Mount Everest back into space at escape velocity, potentially scattering fragments of dinosaur bones on the Moon.
Moon’s Geology Museum
“The moon offers safe keeping for these ancient rocks,” Cabot said. “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, Venus 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.
Two Critical Factors
Laughlin and Cabot cited two factors supporting their theory. The first is that asteroids hitting Venus are usually going faster than those that hit Earth, launching even more material. The second is that 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,” said Laughlin, who is professor of astronomy and astrophysics at Yale. “The moon’s gravity then aids in sweeping up some of these Venusian arrivals.”
NASA’s Artemis Program
Upcoming missions to the moon could give Cabot and Laughlin their answer. The researchers said NASA’s Artemis program is the perfect opportunity to collect and analyze unprecedented amounts of lunar soil.
Laughlin said 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,” 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.”
In a separate initiative, Breakthrough Listen is funding a research study into the possibility of primitive life in the clouds of Venus. The study is inspired by the discovery, announced last year, of the gas phosphine, considered a potential biosignature, in the planet’s atmosphere. The science team will comprise world-class physicists, astronomers, astrobiologists, chemists and engineers, led by Sara Seager, astrophysicist and planetary scientist at the Massachusetts Institute of Technology.
Dark Patches of the Upper Atmosphere
Venus’ upper atmosphere harbors dark patches –first observed by ground-based telescopes more than a century ago–might be forms of sulfur, ferric chloride or, as Carl Sagan speculated, even microscopic life.
“The dark markings in the Venus clouds have resisted a lot of investigation by remote sensing spectroscopy and remain mysterious. It seems very likely now that we won’t get the answers we want until we analyze them in-situ, preferably with instruments on a floating platform,” wrote Fred Taylor at the University of Oxford in an email to The Daily Galaxy. “I think the cause is more likely to be down to some combination of cloud physics and chemistry than to life,” he continued. “of course any prospect of life is so exciting that we should give a high priority to carrying out suitable investigations as long as the possibility remains. Personally, I don’t think the surface of Venus was ever habitable, but again that is unresolved and a hugely important question to answer with future probe missions.
“It is of course a matter of record now that pieces of the Martian surface have been found on Earth, and must also be on the Moon,” Taylor continued in his email. “Theoretical work shows that the same should be true for Venus, but with a much lower probability, which explains why they haven’t been found yet. Chances are better on the Moon, but of course we have to go there to search for them. They will certainly be interesting once we find them, especially since the surface of Venus is so hard to study with landed vehicles, due to the high temperature and pressure.”
“It will be remarkable if any pieces of Venus can be found on the moon and dated,” Sanjay Limaye told The Daily Galaxy. “Any Venus meteorites that were ejected towards the end of the possible presence of liquid water on the surface will reveal a lot after the meteorite pieces are analyzed,” he added. “Besides presence of water, the pieces may harbor fossils if any life existed at the time of the impact on Venus. Under present day conditions on the Venus surface, it will be a daunting task to find ancient terrains making a search for fossils very challenging”.
Image credit: Venus via Shutterstock License
Your free daily email of stories of space and science –a random journey from Planet Earth through the Cosmos– that has the capacity to provide clues to our existence and add a much needed cosmic perspective in our Anthropocene epoch.