Dear Lily and Heidi,
Well, we don’t know for certain. Looking up to the stars at night, I’ve often wondered if alien cats are out chasing alien mice or taking naps on other planets.
My imagination aside, your questions are like those scientists are asking, too. And it’s no wonder we are so curious.
With billions of planets in our galaxy, including small Earth-like worlds, the possibility of life out there is an exciting thought to many people. So, humans have set out to look for planets that might support life.
In fact, this month scientists announced the Kepler spacecraft’s discovery of Earth’s closest cousin so far. Some are calling it Earth 2.0. It has a Sun just like Earth does and if it has a rocky surface like scientists predict, it might even be a good place to grow plants.
My friend Dirk Schulze-Makuch studies life in the universe as an astrobiologist at Washington State University. He explained that for life to exist on Earth it needs a few ingredients. It needs liquid water, just the right combination of elements, and a source of energy, such as our Sun. These are required for every living thing we know of, from bacteria to plants to intelligent life forms, like humans.
Intelligent life, said Schulze-Makuch, is especially rare.
“For 4.5 billion years, on our planet we’ve only had one species so technologically advanced,” he said. “That’s us.”
But the ingredients for life on Earth might not be the exact same for life on other planets, explained Schulze-Makuch.
He has studied thorny devil lizards in one of Earth’s driest desert environments to find clues about life on Mars. It can be hard for thorny devils to find liquid water in the desert, so they’ve adapted to their environment. They can grab water from the air and use special groves on their spines to get a drink.
Scientists wonder if, just as the thorny devils have adapted to their environment, life forms on other planets may also have adapted to their environments. Scientists also think about how organisms can survive in environments that aren’t like Earth’s.
Take a tiny living thing called the tardigrade. Astronauts, who observed these creatures hanging on to their space shuttle, learned the tardigrade could survive in extreme conditions of space without any kind of space suit.
“The tardigrade shows how amazingly inventive life is once it has originated on a planet,” Schulze-Makuch said. “Not only microbial life, but all life, including multicellular life.”
Schulze-Makuch thinks we will find microbes, such as bacteria or fungi, on other planets in the next ten to twenty years.
“We simply don’t know the answers,” he said. “But if it’s out there we’ll have to go find it.”
I’m keeping my paws crossed for a whole planet of cats. But finding even a tiny organism like a microbe would be a huge discovery. It would change our understanding of life as we know it.
Have a question? Ask Dr. Universe. You can send her an e-mail at Dr.Universe@wsu.edu.