The Atmosphere of an Exoplanet Reveals Secrets About Its Surface

An artist’s concept of active volcanoes on Venus. Credit: NASA/JPL-Caltech/Peter Rubin

As astronomers have begun to gather data on the atmospheres of planets, we’re learning about their compositions and evolution. Thick atmospheres are the easiest to study, but these same thick atmospheres can hide the surface of a planet from view. A Venus-like world, for example, has such a thick atmosphere making it impossible to see the planet’s terrain. It seems the more likely we are to understand a planet’s atmosphere, the less likely we are to understand its surface. But that could change thanks to a new study in the Monthly Notices of the Royal Astrophysical Society.

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It Doesn't Take Much to Get a Runaway Greenhouse Effect

Image credit: NASA
Image credit: NASA

During the 1960s, the first robotic explorers began making flybys of Venus, including the Soviet Venera 1 and the Mariner 2 probes. These missions dispelled the popular myth that Venus was shrouded by dense rain clouds and had a tropical environment. Instead, these and subsequent missions revealed an extremely dense atmosphere predominantly composed of carbon dioxide. The few Venera landers that made it to the surface also confirmed that Venus is the hottest planet in the Solar System, with average temperatures of 464 °C (867 °F).

These findings drew attention to anthropogenic climate change and the possibility that something similar could happen on Earth. In a recent study, a team of astronomers from the University of Geneva (UNIGE) created the world’s first simulation of the entire greenhouse process that can turn a temperate planet suitable for Life into a hellish, hostile one. Their findings revealed that on Earth, a global average temperature rise of just a few tens of degrees (coupled with a slight rise in the Sun’s luminosity) would be sufficient to initiate this phenomenon and render our planet uninhabitable.

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Curiosity Sees Earth and Venus in the Night Skies on Mars

Mars rover Curiosity covered in dust and a combined image it took of Earth and Venus both in the Martian night sky.
Curiosity, seen here covered in dust, took two separate images that have been combined into one showing Earth and Venus in the night sky of Mars.

Normally the images from NASA’s Curiosity rover, currently sitting near “Bloodstone Hill” on Mars, are of alien vistas and rock outcroppings that conspiracy theorists constantly try to anthropomorphize into UFOs.  However, the rover is also excellently positioned to capture a unique perspective of an alien sky.  And that is exactly what it did recently when it captured an image of both Venus and Earth in the same Martian night sky.  The images were actually taken in two separate frames, though the two planets were visible in the sky at the same time.

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