The habitable zone, also known as the “Goldilocks zone,” is the region around a star where conditions may be just right for the existence of liquid water on a planet’s surface. Liquid water is considered a key ingredient for the emergence of life as we know it, so the habitable zone is often seen as a promising target for the search for extraterrestrial life.

In our solar system, the habitable zone is defined as the region around the Sun where the temperature is just right for liquid water to exist on a planet’s surface. This region extends roughly from the orbit of Venus to the orbit of Mars. Venus is too close to the Sun and has a runaway greenhouse effect that has made its surface too hot and inhospitable for life as we know it. Mars, on the other hand, is farther from the Sun and has a thin atmosphere, which has caused its surface to become too cold and dry for liquid water to exist in significant quantities. However, it’s possible that Mars may have had liquid water on its surface in the past, and that microbial life could have emerged and possibly even persisted underground.

watch a video from NASA to learn more