Early in the formation of Jupiter as a planet, it moved closer to and then away from the Sun due to interactions with the planetary disk of the young Solar System, and this movement likely triggered Venus onto a path toward its current, inhospitable state, according to a new paper published in the Planetary Science Journal.
This composite image, taken by JAXA’s Akatsuki spacecraft, shows Venus. Image credit: JAXA / ISAS / DARTS / Damia Bouic.
“Scientists consider planets lacking liquid water to be incapable of hosting life as we know it,” said Dr. Stephen Kane, an astrobiologist in the Department of Earth and Planetary Sciences at the University of California, Riverside.
“Though Venus may have lost some water early on for other reasons, and may have continued to do so anyway.”
“One of the interesting things about the Venus of today is that its orbit is almost perfectly circular,” he added.
“With this project, I wanted to explore whether the orbit has always been circular and if not, what are the implications of that?”
To answer these questions, Dr. Kane and colleagues created a model that simulated the Solar System, calculating the location of all the planets at any one time and how they pull one another in different directions.
They measured how non-circular a planet’s orbit is between 0, which is completely circular, and 1, which is not circular at all. The number between 0 and 1 is called the eccentricity of the orbit.
“An orbit with an eccentricity of 1 would not even complete an orbit around a star; it would simply launch into space,” Dr. Kane said.
“Currently, the orbit of Venus is measured at 0.006, which is the most circular of any planet in our Solar System.”
However, the team’s model shows that when Jupiter was likely closer to the Sun about a billion years ago, Venus likely had an eccentricity of 0.3, and there is a much higher probability that it was habitable then.
“As Jupiter migrated, Venus would have gone through dramatic changes in climate, heating up then cooling off and increasingly losing its water into the atmosphere,” Dr. Kane said.
Earlier this year, astronomers detected phosphine gas in the cloud decks of Venus. In Earth’s atmosphere, phosphine is uniquely associated with anthropogenic activity or microbial presence.
“Phosphine is typically produced by microbes. It is possible that it represents the last surviving species on a planet that went through a dramatic change in its environment,” Dr. Kane said.
“For that to be the case, however, the microbes would have had to sustain their presence in the sulfuric acid clouds above Venus for roughly a billion years since the planet last had surface liquid water — a difficult to imagine though not impossible scenario.”
“There are probably a lot of other processes that could produce the gas that haven’t yet been explored,” he said.
“Ultimately, it is important to understand what happened to Venus, a planet that was once likely habitable and now has surface temperatures of up to 462 degrees Celsius (864 degrees Fahrenheit).”
“I focus on the differences between Venus and Earth, and what went wrong for Venus, so we can gain insight into how the Earth is habitable, and what we can do to shepherd this planet as best we can.”
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Stephen R. Kane et al. 2020. Could the Migration of Jupiter Have Accelerated the Atmospheric Evolution of Venus? Planet. Sci. J 1, 42; doi: 10.3847/PSJ/abae63
This article is based on a press-release provided by the University of California, Riverside.
