When looking for life on other planets, you can compare their atmospheres and orbits.
Atmospheres
- Earth Has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide.
- Venus Has an atmosphere that’s mostly carbon dioxide. Venus also has a surface hot enough to melt lead, a heavy atmosphere, and an extremely volcanic geology.
- Mars Has an atmosphere that’s mostly carbon dioxide. Mars is believed to contain three essential requirements for life: chemical building blocks, a source of water, and a source of energy from volcanoes.
Orbits
- Planets with many neighbors may be better places to look for life.
- Mercury spends more time closest to Earth than the other planets.
NASA’s Nancy Grace Roman Space Telescope and the Wide-Field Infrared Survey Telescope can detect signatures of oxygen, water vapor, or other indications of possible life. However, the search for signs of life could take decades.
Earth, Venus, and Mars are all roughly in the habitable zone of the Sun, but both Venus and Mars have atmospheres comprised mostly of carbon dioxide. In contrast, Earth has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide
Scientists use remote sensing technology and spectroscopy to detect life on other planets.
- Remote sensing technology Uses infrared to search for molecules like water and gases like methane, carbon dioxide, and ozone.
- Spectroscopy Analyzes light from a star that passes through a planet’s atmosphere. The light spectrum looks like a bar code, and the missing slices indicate which chemicals or gases are present.
Scientists can also look for surface features that may indicate life. For example, the simultaneous detection of water, carbon dioxide, and oxygen or ozone could indicate biological processes
Other signs of life on a planet include:
- Orbiting in a zone where liquid water is possible
- Being far enough away from the star so that the surface water does not evaporate
- Detecting a molecule that is only produced by living organisms on Earth
- Detecting a repeating radio signal from an Earth-like exoplanet
- Detecting a substance that on Earth is only produced by living things
The only planet where life has been confirmed to exist is Earth. Earth is located in the “habitable zone” around the sun, where temperatures are just right for liquid water to exist. Earth also has a breathable atmosphere, which is rich in oxygen.
Humans can only live on Earth. Other planets in our solar system lack essential elements of life, like oxygen, water, and air. However, scientists have discovered a large number of exoplanets, but almost none of them could support human life.
Planets that could support a long-term colony
- Moon
- Mars
- Larger moons of the giant planets
Other possibilities
- Setting up a manned outpost on Mars
- Building an artificial space colony
- Traveling to another star system
Universe discoveries 