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Scientists propose new method for detecting surfaces of planets trillions of miles away

“Trace species” in atmospheres can help astronomers zero in on surfaces.

Updated: June 19, 2021 - 8:04pm

The Facts Inside Our Reporter’s Notebook

A group of scientists has proposed a new method for detecting and examining surfaces on exoplanets—planetary bodies located outside of the Solar System trillions upon trillions of miles away.

Scientists have been detecting exoplanets for years through a variety of methods, but the surfaces of these planets remain shrouded in mystery due to their immense distance from Earth. 

In a paper published earlier this month in the Astrophysical Journal, the scientists—located in California and Colorado—noted that “sub-Neptunes,” or planets with sizes between those of Earth and Neptune, are “the most commonly detected exoplanets to date.” 

“However,” they continued, “it remains difficult for observations to tell whether these intermediate-sized exoplanets have surfaces and where their surfaces are located.” 

The scientists in the paper propose that “the abundances of trace species in the visible atmospheres of these sub-Neptunes can be used as proxies for determining the existence of surfaces and approximate surface conditions.”

“Trace species” are gases present in a planet’s atmosphere at considerably lower levels than other, dominant gases. 

The scientists claim that they can determine surface conditions by examining those gases because “the pressure–temperature conditions at the surface determine whether photochemically produced species can be recycled back to their favored thermochemical equilibrium forms and transported back to the upper atmosphere.”

The researchers claim that they successfully modeled the surface of K2-18b, a planet located over 120 light-years from Earth. “This framework can be applied together with future observations to other sub-Neptunes of interest,” they said.