Using data from Spitzer and TESS, scientists discover exoplanet littered with volcanoes

by Haygen Warren

Using data collected by NASA’s retired Spitzer Space Telescope and NASA’s Transiting Exoplanet Survey Satellite (TESS), a team of scientists has discovered an exoplanet that could potentially be covered with volcanoes. The exoplanet is Earth-sized, and the team’s results suggest that the gravitational pull of a neighboring exoplanet could be causing an increase in volcanic activity on the exoplanet.

If the results and conclusions from the team, which is led by Merrin Peterson of the Trottier Institute for Research on Exoplanets (iREx) at the University of Montreal, are true, the exoplanet, named LP 791-18 d, could be extremely similar to one of Jupiter’s four Galilean moons, Io — which is the most volcanically active celestial body in our solar system — and undergo regular outbursts of volcanic activity.

“LP 791-18 d is tidally locked, which means the same side constantly faces its star. The day side would probably be too hot for liquid water to exist on the surface. But the amount of volcanic activity we suspect occurs all over the planet could sustain an atmosphere, which may allow water to condense on the night side,” said co-author Björn Benneke, who is also based out of iREx.

Figure showing the orbital separations of the three planets within the LP 791-18 system. (Credit: Peterson et al.)

Located approximately 90 light-years away in the constellation Crater, LP 791-18 d orbits a small red dwarf star. The red dwarf’s star system not only consists of LP 791-18 d but two additional exoplanets, named LP 791-18 b and c, both of which were discovered before LP 791-18 d. The innermost planet, LP 791-18 b, is 20 percent larger than Earth, while the outer planet, LP 791-18 c, is 2.5 times the size of Earth and more than seven times Earth’s mass. Given the increased mass of LP 791-18 c, the planet has a greater gravitational pull than both LP 791-18 b and d.

When orbiting around their host star, LP 791-18 c and d’s orbits bring the planets extremely close to one another. When the planets ultimately pass one another, the gravity from LP 791-18 c tugs on the surface of LP 791-18 d, causing internal friction to occur within LP 791-18 d. This internal friction then produces and increases volcanic activity on the planet’s surface.

“A big question in astrobiology, the field that broadly studies the origins of life on Earth and beyond, is if tectonic or volcanic activity is necessary for life. In addition to potentially providing an atmosphere, these processes could churn up materials that would otherwise sink down and get trapped in the crust, including those we think are important for life, like carbon,” said Jessie Christiansen, co-author and scientist at NASA’s Exoplanet Science Institute at the California Institute of Technology in California.

This exact same process occurs on Io, with the gravitational pull of the other three Galilean moons and Jupiter leading to Io’s surface being stretched and contracted — which then causes an increase in volcanic activity. Io’s extreme volcanism has been observed by a plethora of missions, with NASA’s New Horizons mission even capturing a volcano erupting on Io’s surface when it flew past Jupiter in February 2007.

New Horizon’s image of a volcano erupting on Io. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

In addition to its volcanic surface, LP 791-18 d sits on the edge of its host star’s habitable zone, or the region around a star wherein conditions are favorable for the formation of liquid water on planets. If Peterson et al.’s predictions about LP 791-18 d’s geologic activity are correct, the team believes that the planet’s volcanism and location within the habitable zone means that the formation of an atmosphere is possible. Furthermore, the temperatures on the night side of LP 791-18 d could be low enough for water to condense on the planet’s surface.

While no future observations of LP 791-18 d have been announced, NASA’s powerful James Webb Space Telescope will soon be used to observe LP 791-18 c. Webb’s observations of LP 791-18 c will provide Peterson et al. with valuable information that will help them further understand how LP 791-18 d’s volcanism is produced.

As mentioned, the team’s results utilized data from NASA’s retired Spitzer infrared space telescope. Specifically, Peterson et al. used data Spitzer collected when observing LP 791-18 d’s star system as a whole. Spitzer’s observations of the system were among the last observations the telescope would take before it was decommissioned in January 2020.

“It is incredible to read about the continuation of discoveries and publications years beyond Spitzer’s end of mission. That really shows the success of our first-class engineers and scientists. Together they built not only a spacecraft but also a data set that continues to be an asset for the astrophysics community,” said Spitzer project manager Joseph Hunt.

Peterson et al.’s research was published in the journal Nature on May 17.

(Lead image: Artist’s illustration of  LP 791-18 d. Credit: NASA’s Goddard Space Flight Center/Chris Smith (KRBwyle))

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