NASA: Exoplanet research begins this summer – What their surface will show us

The big summer of space exploration will be this year for NASAas both the Artemis program, which concerns the colonies on the Moon and Mars, and the study of exoplanets that have been found and which – in the distant future – could be a possible human destination are in full swing.

NASA will begin observing specific exoplanets this summer. Among the studies planned for the first year are studies of two warm-earth planets characterized as “super-Earth” for their size and rocky composition: the lava-covered 55 Cancri e and the airless LHS 3844 b. Researchers will focus Webb’s high-precision spectrographs on these planets to understand the geological diversity of planets across the galaxy and the evolution of rocky planets such as Earth.

Super-Hot Super-Earth 55 Cancri e

The planet Cancri e orbits less than 1.5 million miles from its Sun-like star (one-twenty-fifth the distance between Mercury and the Sun), completing a circuit in less than 18 hours. With surface temperatures well above the melting point of typical rock-forming minerals, the daytime side of the planet is believed to be covered by lava oceans.

Planets orbiting so close to their star are thought to be tidal locked, with one side facing the star on a permanent basis. As a result, the hottest spot on the planet should be the one that sees the star most directly, and the amount of heat coming from the day side should not change much over time. That was the initial assessment. Observations of the 55 Cancri e by NASA’s Spitzer Space Telescope showed that the hottest region shifts from the part that sees the star most directly, while the total amount of heat detected by the day side varies.

Does the 55 Cancri e have a thick atmosphere?

One explanation for these observations is that the planet has a dynamic atmosphere that moves heat around. “The 55 Cancri e could have a dense atmosphere dominated by oxygen or nitrogen,” said Renyu Hu of NASA’s Jet Propulsion Laboratory in Southern California, who leads a team that will use the near-infrared (NIRCam) camera. and the medium infrared (MIRI) instrument. ) to capture the heat emission spectrum of the planet’s day. “If it has an atmosphere, we can detect it and determine what it consists of,” Hu added.

Is it raining lava at night at 55 Cancri e?

Another interesting possibility, however, is that the 55 Cancri e is not tidal locked. Instead, it can be like Mercury, rotating three times for every two orbits. As a result, the planet will have a day-night cycle.

“This could explain why the hottest part of the planet is shifting,” said Alexis Brandeker, a researcher at Stockholm University who leads another team studying the planet. “Just like on Earth, it would take time for the surface to heat up. The hottest time of the day would be in the afternoon, not exactly at noon. “

In this scenario, the surface would heat up, melt, and even evaporate during the day, creating a very subtle atmosphere. At night, the steam would cool and condense to form lava droplets that would rain on the surface and solidify again as night fell.

The coldest Super-Earth LHS 3844 b

While 55 Cancri e will provide information on the exotic geology of a lava-covered world, LHS 3844 b provides a unique opportunity to analyze solid rock on an exoplanet surface.

Like the 55 Cancri e, the LHS 3844 b orbits very close to its star, completing a spin in 11 hours. However, because its star is relatively small and cool, the planet is not hot enough to melt the surface. In addition, Spitzer’s observations show that the planet is very unlikely to have a substantial atmosphere.

What is the surface of LHS 3844 b made of?

While we will not be able to image the surface of the LHS 3844 b directly with the Webb, the lack of a dark atmosphere makes it possible to study the surface by spectroscopy. “It turns out that different types of rock have different spectra,” explained Laura Kreidberg at the Max Planck Institute for Astronomy. “You can see with your own eyes that granite is lighter than basalt. “There are similar differences in the infrared light emitted by rocks.”

Kreidberg’s team will use MIRI to capture the daytime heat emission spectrum of LHS 3844 b and then compare it to known rock spectra, such as basalt and granite, to determine its composition. If the planet is volcanically active, the spectrum could also reveal the presence of traces of volcanic gases.

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