Searching for Life in our Solar System

Titan in Natural Color

Astrobiology is the study and search for extraterrestrial life – exotic life forms existing on other celestial bodies. While studies are underway searching for intelligent life throughout the galaxy such as SETI, there are a few places astrobiologists are looking in our own solar system.


Titan is the largest moon of Saturn, almost twice the size of our own moon. It is a unique celestial body in our solar system, in that it is the only satellite with a dense atmosphere, and has evidence of liquid on its surface.

Artist rendering of Titan’s Methane lakes

Titan’s atmosphere is primarily made up of Nitrogen, and is much thicker than Earth’s. This makes it extremely opaque, and for many years we had no idea what the surface looked like. In 1995 Hubble used its infrared instruments to image the surface of Titan, and discovered shallow lakes of liquid methane on the surface.

These lakes may support life, in a way that Earth’s oceans do. Instead of carbon based life, these creatures could be methane based, where they would inhale Hydrogen, and exhale methane. While no concrete evidence of these exotic life forms exists, the necessary building blocks are there. There are numerous plans to return to Titan (the Huygens probe landed on the surface in 2005), though none have been funded as of yet.


Enceladus’ icy surface

Enceladus is a small moon that orbits Saturn. It is only about 500km across, or about 13% the width of our moon. It exists about 238,000km away from the surface of Saturn, and takes 218 days to orbit.

Enceladus has recently been deemed the most habitable spot in the solar system beyond Earth. This is because Enceladus is covered in water ice, and is also extremely geologically active. At the southern end of the moon, giant plumes of liquid water spray out of the icy surface like geysers. These jets of water, known as cryovolcanoes, turn to vapor and give Enceladus the most notable atmosphere of any solar system moon outside of titan. The jets also indicate the core of the moon is warm due to tidal heating from Saturn’s gravity, which could allow for a water ocean underneath the ice. Fractures and a relatively low number of impact craters indicate the entire surface is tectonically active – another sign the moon is warm in its core.

Enceladus’ Cryovolcanoes

This warmth, along with water oceans, may lend itself towards the existence microbial extremophiles, if the hot rocky core is releasing its energy through hydrothermal vents. The existence of life using this method can be seen on Earth at extremely deep and geologically active points in the ocean, where no energy by means of sunlight can be utilized.


View of Europa’s Icy Surface

Europa is the fourth largest moon of Jupiter, only slightly smaller than our own moon. It is similar to Enceladus in that it is covered in water ice, and also believed to be warm at its core due to tidal heating from Jupiter’s gravitational pull. As with Enceladus, this could also harbor microbial life at or near hydrothermal vents. Additionally, it has been calculated cosmic radiation could convert some of the oxygen locked up in the surface ice into free oxygen in the oceans beneath. This could conceivably support larger life forms, such as small fish.

While Europa is thought to be one of the best chances for finding life in the solar system, the likelihood of a very thick ice shell makes it difficult to access the inner ocean. However, In December 2013 it was discovered that Europa also has large plumes of water, some as high as 200km, ejecting out of its surface, similarly to Enceladus. If these jets are releasing water from the subsurface oceans, it would be relatively easy for orbiting spacecraft to study the chemical makeup of the water vapor, and determine if life does in fact reside there.

Rendering of the proposed interior of Europa

Recently the US House Appropriations Committee has supplied $80 million in funding for the creation of future Europa exploration missions. These missions include Europan flybys, orbits, and eventually landing on the surface. These missions ultimately are intended to determine the likelihood of extra terrestrial life on Europa. Additionally, the Jupiter Icy Moons Explorer (JUICE), was recently approved by the European Space Agency, which will spend some time observing Europa. This mission is set to launch in 2022.

One Response to “Searching for Life in our Solar System”

  • Steve Heikkinen says:

    Thought you might want to see/share this:

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