No concrete evidence of life has yet been found on any celestial body other than Earth. Yet many scientists are convinced that this is simply a matter of time. Space researchers are planning future space missions to search for carbon-based life as we know it. Alongside Mars, another potential host of life in our solar system is Titan, one of Saturn’s moons. Since Saturn is quite far from the Sun, it is relatively cold there – yet the huge gravitational pull of the ringed planet causes the largest moon in its orbit to flex, creating a layer of liquid water under Titan’s icy surface. Researchers believe these to be ideal conditions for life.
A particular challenge in space missions such as the Mars rover missions is to avoid bringing tiny microorganisms from Earth to the celestial body being explored. This kind of “planetary contamination” would invalidate any sensational news reports about the discovery of life forms.
In addition to the search for extra-terrestrial life in our solar system, astronomers are looking for “extrasolar planets” (“exoplanets” for short), which orbit stars other than the Sun. Up until the early 1990s, they were believed to exist, but none had yet been found. Almost 2,000 exoplanets have since been discovered. Some of these are located in the “habitable zone”, meaning that they are at the right distance from their central star to allow for temperatures at which liquid water can exist. Such exoplanets are also potential hosts of extra-terrestrial life, although that is not necessarily intelligent life.
A whole new element is introduced to the question when time is factored in. The universe is almost 14 billion years old, with no foreseeable end point. On this extraordinarily long timescale, intelligent life has only existed on Earth for the blink of an eye. Discovering a developed life form is therefore not just a question of place, but also one of time – which makes the chances even lower. Given that humanity may destroy itself through war or climate change, or that it could be wiped out by a cosmic impact, it is clear that timeframes pose a real problem in the quest to find other life forms.
This question was answered by Henning Krause from the Department of Communications and Media Relations at the Helmholtz Association.