Life in Space?

Earth is the only place in our solar system known to host living things. But scientists continue to search the seven other planets, five dwarf planets, and more than 200 moons for the smallest signs of life. 

Earth is the only place in our solar system known to host living things. But scientists continue to search the seven other planets, five dwarf planets, and more than 200 moons for the smallest signs of life. 

ENVIRONMENT: rocky surface, with a hot, thick atmosphere made of toxic gas and clouds

ENVIRONMENT: rocky surface, with a hot, thick atmosphere made of toxic gas and clouds

Venus is the second planet from the sun. That makes it scorching hot. Its rocky surface reaches temperatures of more than 470°C (878°F)! That’s much too hot for any living thing on Earth to survive. For that reason, Venus has always seemed like an unlikely place for life.

But last year, scientists made an exciting discovery. Researchers used powerful telescopes to look closely at Venus’s atmosphere. In that layer of gases surrounding the planet, they found a chemical called phosphine. On Earth, phosphine is made only by microscopic organisms called microbes. 

Venus is the second planet from the sun. That makes it really hot. Its rocky surface reaches temperatures that are higher than 470°C (878°F)! That’s too hot for any living thing on Earth. For this reason, Venus has seemed like an unlikely place for life.

But scientists made an exciting discovery last year. They used powerful telescopes to look closely at Venus’s atmosphere. That’s the layer of gases around the planet. There, they found a chemical called phosphine. Phosphine on Earth is made only by microbes. These living things are too small to see without a microscope.

Could the phosphine in Venus’s clouds have been made by alien microbes? Unlike Venus’s surface, the clouds are 30° to 70°C (86° to 158°F)—cool enough to host life. “If there is life there, it’s hard to imagine what it might be like,” says Clara Sousa-Silva. She’s a scientist at Harvard University in Massachusetts who worked on the study.

When other research groups tried to detect phosphine in Venus’s atmosphere, only one team could. That led some scientists to doubt Sousa-Silva’s discovery. Now, Sousa-Silva’s team is looking for phosphine again to ensure the findings are correct. “This is exactly how science works,” says Sousa-Silva.

Could alien microbes have made the phosphine in Venus’s clouds? Unlike Venus’s surface, the clouds are 30° to 70°C (86° to 158°F). That’s cool enough for life to exist. “If there is life there, it’s hard to imagine what it might be like,” says Clara Sousa-Silva. She’s one of the study’s scientists. She works at Harvard University in Massachusetts. 

Other scientists tried to detect phosphine in Venus’s atmosphere. But only one team could. That led to some doubt about Sousa-Silva’s discovery. Now, her team is checking to make sure the findings are correct. “This is exactly how science works,” she says.

ENVIRONMENT: about the size of Earth’s moon; extremely cold, with a frozen surface and a thin atmosphere

ENVIRONMENT: about the size of Earth’s moon; extremely cold, with a frozen surface and a thin atmosphere

Jupiter, the largest planet in our solar system, has 79 moons. Its fourth-largest moon, Europa, is covered in a thick layer of ice. Beneath this icy shell is a giant ocean of liquid water. Scientists think that this ocean could be home to alien life.

Openings on the moon’s ocean floor gush hot water that’s full of minerals. These openings are similar to formations on Earth’s ocean floor called deep-sea hydrothermal vents. Heat from those vents could warm the water enough for life to exist, scientists say. The minerals could provide nutrients to feed microbes.

NASA hopes to someday send a spacecraft to Europa. It would orbit, or circle around, the moon to capture spray from the vents that might have escaped into space. If life does exist in Europa’s ocean, the water might contain chemicals made by microbes—or other life-forms! Another mission could drill through Europa’s ice and send a robot into the ocean to look for signs of life.

Jupiter is the largest planet in our solar system. It has 79 moons. Its fourth-largest moon is Europa. It’s covered in a thick layer of ice. Beneath the ice is a giant ocean of liquid water. Scientists think it could be home to alien life.

Openings on the moon’s ocean floor gush hot water that is full of substances called minerals. The openings are like ones on Earth’s seafloor called deep-sea hydrothermal vents. Heat from those vents could warm the water enough for life to exist. And microbes could feed on the minerals.

NASA hopes to someday send a spacecraft to Europa. It would orbit, or circle around, the moon. It would capture spray from the vents that might have reached space. The water might contain chemicals made by microbes or other life-forms! Another mission could drill through Europa’s ice. Then a robot could enter the ocean to look for signs of life.

ENVIRONMENT: extremely cold with a dry, rocky surface and frozen water near poles

ENVIRONMENT: extremely cold with a dry, rocky surface and frozen water near poles

Today, the surface of Mars looks like a vast desert. But scientists think it was once covered in oceans that could have supported life. Four billion years ago, Mars lost its magnetic field. Over time, it lost its atmosphere as well. Without that protective layer of gases, its liquid water evaporated, floating away into space. The planet turned into a cold, dry wasteland.

Scientists think it’s likely that microbes once lived in Mars’s ancient oceans. They also think microscopic organisms could still be buried below the planet’s surface, where there may still be liquid water, says Sarah Hörst. She’s a planetary scientist at Johns Hopkins University in Maryland.

Today, the surface of Mars looks like a vast desert. But scientists think it was once covered in oceans. They could have held life. Mars lost its magnetic field 4 billion years ago. Over time, it lost its atmosphere as well. Without that layer, the liquid water on Mars evaporated, or changed into a gas. It floated away into space. The planet turned cold and dry.

Scientists think it’s likely microbes once lived in Mars’s ancient oceans. They also think microbes could still be buried below the planet’s surface. That’s where there may still be liquid water, says Sarah Hörst. She’s a planetary scientist. She works at Johns Hopkins University in Maryland.

In February 2021, a NASA rover called Perseverance arrived on Mars. One of its missions is to search for signs of life there. The rover will move around, collecting dirt and rock samples. These samples will be left in tubes on the planet’s surface and picked up on a later mission. Back on Earth, scientists will study the bits of dirt and rock to look for clues that life did, and possibly still does, exist on Mars.

A NASA rover landed on Mars in February 2021. Its name is Perseverance. One of its missions is to search for signs of life there. The rover will explore Mars. It will collect dirt and rock samples. These samples will be left in tubes on the planet’s surface. They’ll be picked up on a later mission. Scientists will study the bits of dirt and rock back on Earth. They’ll look for clues that life did, and maybe still does, exist on Mars.