Study narrows James Webb Space Telescope targets

In the first paper to compile all known information about Venus-like planets beyond our solar system, scientists are the closest they’ve come to finding an analog of Earth’s “twin.”

If they succeed in finding one, it could reveal important insights into Earth’s future, and our risk of developing a runaway greenhouse climate like Venus did.

The scientists who wrote the paper started with more than 300 known terrestrial planets that orbit other stars, called exoplanets. They chose to list up to five that most likely resemble Venus in terms of their radii, masses, densities, shapes of their orbits, and perhaps most importantly, distances from their stars.

the paper, published in The Astronomical Journalalso ranked the most Venus-like planets in terms of the brightness of the stars they orbit, raising the possibility that the James Webb Space Telescope will pick up more informative signals about the composition of their atmospheres .

Today’s Venus floats in a nest of sulfuric acid clouds, is devoid of water, and features surface temperatures of up to 900 degrees Fahrenheit—hot enough to melt lead. Using the Webb telescope to observe these possible Venus analogs, or “exoVenuses,” scientists hope to find out if things are different for our Venus.

“One thing we wondered about was whether Venus might once be habitable,” said Colby Ostberg, lead author of the study and UC Riverside Ph.D. student. ‘To confirm this, we want to look at the coolest of the planets at the outer edge of the Venus zone, where they get less energy from their stars.’

The Venus Zone is a concept suggested by UCR astrophysicist Stephen Kane in 2014. This is similar to the concept of a habitable zone, which is a region around a star where liquid water can exist on the surface.

“The Venus Zone is where it would be too hot to have water, but not hot enough for the planet’s atmosphere to be removed,” Ostberg explained. “We want to find planets that still have significant atmospheres.”

Finding a planet similar to Venus in terms of the planet’s mass is also important because mass affects how long a planet is able to maintain an active interior, with the movement of rocky plates in its outer shell. which is known as plate tectonics.

“Venus has 20% less mass than Earth, and as a result, scientists believe that there may not be any tectonic activity there. Therefore, Venus has difficulty removing carbon from its atmosphere,” explained by Ostberg. “The planet just can’t get rid of it.”

Another aspect of an active planetary interior is volcanic activity, and evidence discovered just this month suggests that Venus still has active volcanoes. “The large number of Venus analogues identified in our paper will allow us to test whether such volcanic activity is common to similar planets, or not,” said Kane, who co-authored the study. .

The research team proposes the planets identified in the paper as targets for the Webb telescope in 2024. Webb is the most expensive and advanced observing tool ever created and will allow scientists to not only see if the exoVenuse has atmospheres, but also what they ‘ remade of.

Webb observations may reveal biosignature gases in the atmosphere of an exoVenus, such as methane, methyl bromide or nitrous oxide, which may indicate the presence of life.

“Detecting molecules in an exoVenus would show that habitable worlds could exist in the Venus Zone and strengthen the possibility of a temperate period in Venus’ past,” Ostberg said.

These observations will be complemented by two upcoming NASA missions to Venus, in which Kane will play an active role. The DAVINCI mission will also measure gases in the Venusian atmosphere, while the VERITAS mission will enable 3-D reconstructions of the landscape.

All of these observations lead to the ultimate question that Kane poses in much of his work, which attempts to understand the Earth-Venus climate difference: “Is Earth the odd one out or is Venus the odd one out?”

“It could be that one or the other evolved in an unusual way, but that’s hard to answer when we only have two planets to examine in our solar system, Venus and Earth. The differences we see,” Kane said.

If the planets in the new list are similar to Venus, it will show that the outcome of Venus’ evolution is normal.

“That will 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,” Kane said.