![]() ![]() The majority of stars are cool, red, smaller stars. But that depends on how far away the planet is from the star and what kind of star it is, because stars emit light at different wavelengths, and the majority of stars in the galaxy are not like the sun. But if the atmosphere is too thin to support liquid water on the surface, we might get a Mars-and liquid water could not flow on Mars’ surface today, because of its thin atmosphere.Īn Earth atmosphere might work. We don’t want too thick of an atmosphere on an exoplanet because that could create a Venus, heating up the planet. We change the host star, we change the atmosphere, we change the surface, and we see what the climates could be, based on the information we have about the planet. We’re using them to predict the climate on these exoplanets. We use models that were historically used to predict climate and weather on the Earth, predicting the effect of climate change through the 2100s. The climate and the weather on another planet can be impacted by so many things. We did detect a glint from Cassini’s mission, but that glint was coming off of liquid ethane and methane lakes. If we could look for a glint of liquid on the surface-the fancy word for that is “specular reflection”-that would tell us there’s a liquid there. So we’re thinking about a suite of atmospheric gases, and maybe even surfaces. So if there’s a lot of oxygen in the atmosphere, and if we use that as our only criterion for life being present, that could be a false positive. ![]() CO 2 goes into the atmosphere and it’s split apart by light. Though we know a lot of life on Earth needs oxygen, not every type of life needs oxygen, and oxygen can be created by volcanoes. We call them biosignatures, signs of biologically generated global impacts on a planet’s atmosphere or surface that we can observe remotely that would tell us unequivocally that life is present. That’s tricky, because it requires us to come up with a recipe of signs we could take out from the atmosphere. If we were looking at an exoplanet like our Earth, could we tell that it might be habitable-or even inhabited? Those are the planets that we’d like next-generation telescopes to follow up on, to look for signs of life. Then we identify those planets that seem to be the most habitable across the widest range of these atmospheres and surfaces, and maybe even orbital configurations. OK, we don’t know what its atmosphere is like, but what kind of atmosphere would allow it to support liquid water on its surface? What kind of surfaces-when interacting with the host star’s light-would generate a climate that’s warm enough for liquid water but not too warm to evaporate it out into space? With computer modeling, we can put in information we have about a planet’s environment, and we can fill in the gaps. Once planets are discovered, I get to find out how habitable they really are-because there’s not a whole lot we know about these planets that are Earth-sized that we find. The way I do that now is using computer models.
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