Why is Earth the only planet with living things?

Nina Amatulli, in the second grade at the American School in Japan, had a question to ask scientists.

Nina Amatulli: Why is Earth the only planet with living things?

Earth scientist Robert Hazen of the Carnegie Institution For Science answered her. Hazen is an expert on the chemistry and origin of life throughout the universe.

Robert Hazen: You know Nina, this is a really great question. A lot of us still hold out hope that there’s life on Mars and other nearby planets and moons. We think that there’s a really good chance that microbes can eke out a living beneath the surface. Life needs water, and there’s a good chance warm and wet environments exist near the surface of Mars.

Hazen agrees though, that at least in our solar system, Earth is likely the only planet with land plants and animals.

Robert Hazen: Animals face the additional challenge of needing lots of energy to hunt for food, to escape predators. And on Earth, animals only appeared after microbes made lots of oxygen, and that allows fast metabolism, and after plants, which provide food. But, that’s just our solar system. And we suspect that there are countless trillions of solar systems out there in the universe. Given that abundance, my guess is that there are lots of other living worlds out there.

Our thanks to the Monsanto Fund, bridging the gap between people and their resources.

Our thanks to:
Robert M. Hazen
Carnegie Institution for Science
Geophysical Laboratory
Washington, DC