card
069

extraterrestrial life

OLogy Series
astronomy
card
069

extraterrestrial life

OLogy Series
astronomy

Are we alone in the Universe? There are billions of stars in our galaxy, and 100 billion galaxies in our Universe. We don't know how many planets there are, or how many of these planets might have life on them. We've found some planets outside our solar system, but none seem to have conditions needed for life.

Search for Extraterrestrial Intelligence
The first large-scale search for intelligent extraterrestrial life began in 1959, when radio telescopes were first put into use. SETI (Search for Extraterrestrial Intelligence), an organization founded to look for signals of life from outside our solar system, began to use giant radio telescopes to scan the sky for specific patterns of radio waves. On Earth, we create radio waves to transmit information, like for television and radio. The radio waves we create on Earth are very different than the natural radio waves in space. SETI monitors radio waves from space in the hope that they'll detect patterns of waves that look different from ours and from other radio waves we're used to detecting from space. This might tell us that someone else out there is using radio waves, too. If one of these signals is found, its source will be investigated... Stay tuned.

Which of the following is necessary for life as we know it?

liquid water

ice cream

sunlight

Are you right?

Correct!

Liquid water is just one of the things that must be present in order for life to exist. Life also needs warmth and certain chemical ingredients.

Which planet have scientists studied most closely for signs of life?

Jupiter

Pluto

Mars

Are you right?

Correct!

Like Earth, Mars has solid water in the form of polar ice caps. Liquid water, a requirement for life, may have once flowed on Mars' surface. Scientists are still looking. If they do find life, it's expected to be microscopic.

Neil Tyson, astrophysicist

Given the sheer scale of the Universe, and how quickly life evolved on Earth . . . there's no question that life exists elsewhere . . .

Evidence: so far, there is no evidence of life anywhere in the Universe but on Earth
Current Research: we're looking for extra-solar planets, searching for water on other planets in the solar system, monitoring radio waves from deep space, and learning to recognize what life might be like elsewhere by studying life in
extreme environments on Earth
Importance: to help us understand our origins and who our neighbors might be

Image credits: Jim Steck and Daryl Collins; Neil Tyson: AMNH.