Scientists use moon as a mirror to study Earth during lunar eclipse

I note this in the report. "One of NASA's major goals is to identify planets that could support life," Youngblood said. "But how would we know a habitable or an uninhabited planet if we saw one? What would they look like with the techniques that astronomers have at their disposal for characterizing the atmospheres of exoplanets? That's why it's important to develop models of Earth's spectrum as a template for categorizing atmospheres on extrasolar planets."

A good idea. Exoplanet atmospheres, presently are very difficult to detect and determine properties. The TRAPPIST-1 system, some models indicate they may have atmospheres, also perhaps no atmosphere on these 7 exoplanets. 'A review of possible planetary atmospheres in the TRAPPIST-1 system', https://arxiv.org/abs/2007.03334, 07-July-2020. “TRAPPIST-1 is a fantastic nearby (~39.14 light years) planetary system made of at least seven transiting terrestrial-size, terrestrial-mass planets all receiving a moderate amount of irradiation...This means they likely have either (i) a high molecular weight atmosphere or (ii) no atmosphere at all. There are several key challenges ahead to characterize the bulk compositions of the atmospheres (if present) of TRAPPIST-1 planets."

Some hot jupiters are reported with atmosphere properties observed now, 'Astronomers see unexpected molecule in exoplanet atmosphere', https://phys.org/news/2020-06-astronomers-unexpected-molecule-exoplanet-atmosphere.html

"SRON-astronomers have found the signature for aluminum oxide (AlO) in the spectrum of exoplanet WASP-43b. This came as a surprise because AlO is expected to stay hidden in the lower atmospheric layers. It is only the second time that astronomers have observed the molecule in an exoplanet's atmosphere. "

WASP-43b is about 284 LY distance from Earth. TRAPPIST-1 system about 39 LY distance. These exoplanets and others are difficult to measure and determine atmosphere properties - at present.
 

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