![]() Some moons of Saturn and Jupiter (including Europa, we suspect) are ocean worlds – they have oceans beneath their icy surfaces. ![]() That region is the star’s habitable zone or "Goldilocks zone.” But scientists have learned that worlds outside the Goldilocks zone can have liquid oceans as well, including several moons in our outer solar system. It Matters Where We Find LifeĪround most stars is a region where conditions are just right for an orbiting planet to have liquid water on its surface. An ocean world that could have supported life is now a frigid, nearly airless desert.īut more exotic worlds farther from the Sun host vast oceans in the present day. Solar wind and radiation stripped away the Martian atmosphere. Then, over millions of years, Mars lost most of the water that was on its surface. Indeed, scientists think Mars was once habitable. A few billion years ago, an ocean may have covered one-fifth of the Martian surface. Generations of rovers and landers have taught us much about the Red Planet. But Mars offers a more tolerable environment than Venus for any plucky probes that reach the Martian surface intact. Landing on Mars is notoriously difficult. ![]() The planet’s climate is nearly as damaging to robotic probes as it would be to humans. Even if evidence for life were sitting on the planet’s surface, searching for it would be challenging. The planet’s atmospheric pressure would crush a human, and temperatures reach 864 degrees Fahrenheit (462 degrees Celsius). As it happens, Earth’s planetary neighbors may have once been wetter.įor as long as 2 billion years, liquid water may have covered much of the surface of Venus. ![]() So water’s presence or absence is an initial way to assess a world’s habitability. Probing Planets’ PastsĪlmost everywhere we find water on Earth, we also find life. But to understand why it’s a uniquely captivating target for astrobiology, it helps to know a bit about a few other moons and planets in the solar system. They’ve found that life as we know it requires three main ingredients: temperatures that allow liquid water to exist the presence of carbon-based molecules and an energy input, such as sunlight.Įuropa seems to have all three ingredients. Scientists study the origin, evolution, distribution, and future of life in the universe in a scientific field called astrobiology. Jupiter’s icy moon Europa may be the most promising place in the solar system to find present-day environments suitable for life beyond Earth. ![]()
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