Scientists are honing their search for a planet like Venus beyond our solar system, with the publication of the first-ever paper compiling all available information. The ultimate goal is to find a twin of Earth that could unlock vital insights into our planet’s future and help mitigate the risk of a catastrophic greenhouse climate like Venus.
The authors of the paper initiated their research by analyzing over 300 known exoplanets that are similar to terrestrial planets. Through a thorough selection process, they identified the five most promising candidates that share similarities with Venus in terms of their mass, density, radii, and orbital characteristics, among other factors.
Moreover, the researchers classified the Venus-like planets according to the brightness of the stars they orbit, which amplifies the probability of the James Webb Space Telescope capturing more precise information about their atmospheric composition.
Their findings were recently published in The Astronomical Journal.
In its current state, Venus is enveloped by clouds of sulfuric acid, devoid of water, and boasts surface temperatures that can soar up to 900 degrees Fahrenheit – a temperature hot enough to liquefy lead. By utilizing the capabilities of the Webb telescope to investigate these potential Venus counterparts, also known as “exoVenuses,” scientists aim to uncover the possibility of a past Venus that was once hospitable to life.
“One thing we wonder is if Venus could once have been habitable,” adds lead author Colby Ostberg.
And “to confirm this, we want to look at the coolest of the planets in the outer edge of the Venus zone, where they get less energy from their stars.”
In 2014, Stephen Kane, an astrophysicist at UCR, introduced the concept of the Venus Zone. This idea is comparable to the habitable zone, a region surrounding a star where liquid surface water could potentially exist.
The Venus Zone, on the other hand, is an area where the temperature is too high for water to exist but not so high that the planet’s atmosphere is stripped away.
According to Ostberg, the purpose of identifying planets within the Venus Zone is to locate those that still possess significant atmospheres.
The mass of a planet is a crucial factor in determining the duration of its active interior and plate tectonics, which is the movement of rocky plates across its outer shell. Therefore, discovering a planet with a mass similar to that of Venus is significant.
According to Ostberg, Venus has about 20% less mass than Earth, which may account for the absence of tectonic activity on the planet. This lack of tectonic activity makes it challenging for Venus to eliminate carbon from its atmosphere. As a consequence, the planet is unable to effectively remove carbon from its atmosphere.
“The planet just can’t get rid of it.”
Volcanic activity is another indication of an active planet interior, and recent findings suggest that Venus may still have active volcanoes. These discoveries were made earlier this month.
“The large number of Venus analogs identified in our paper will allow us to test if such volcanic activity is the norm amongst similar planets, or not,” adds Kane, who co-authored the study.
The team of researchers has recommended the planets mentioned in the paper as potential targets for the Webb telescope in 2024. The Webb telescope is the most advanced and costly observation instrument ever developed, providing scientists with the ability to detect not only the presence of atmospheres in the exoVenuses but also their composition.
By examining the exoVenus atmospheres, the Webb telescope could potentially identify biosignature gases such as methane, methyl bromide, or nitrous oxide that may indicate the presence of life. These observations could potentially reveal the existence of life on these planets.
“Detecting those molecules on an exoVenus would show that habitable worlds can exist in the Venus Zone and strengthen the possibility of a temperate period in Venus’ past,” Ostberg adds.
NASA’s two upcoming missions to Venus, in which Kane will have an active involvement, will complement these observations. The DAVINCI mission will assess the gases present in the Venusian atmosphere, while the VERITAS mission will allow for 3D reconstructions of the landscape.
All of these observations are leading to the ultimate question that Kane addresses in much of his research, which aims to comprehend the differences between Earth and Venus’ climate: “Is Earth weird or is Venus the weird one?”
“It could be that one or the other evolved in an unusual way, but it’s hard to answer that when we only have two planets to analyze in our solar system, Venus and Earth. The exoplanet explorations will give us the statistical power to explain the differences we see,” Kane adds.
Should the planets on the new list be confirmed to have similarities to Venus, it would suggest that the outcome of Venus’ evolution is a widespread occurrence.
“That would be a warning for us here on Earth because the danger is real. We need to understand what happened there to make sure it doesn’t happen here.”
Image Credit: NASA/JPL