LifeDescribe some of the methods that astronomers use to obtain evidence for life (past or present) elsewhere in our Solar System
Scientists agree that if life (past or present) is to be found elsewhere in the Solar System that it will likely be carbon based and have required water to form and survive. Scientists are interested in water in any form throughout the Solar System.
It is unlikely that life exists in the human or animal forms that we’re familiar with, due to a lack of breathable oxygen or an appropriate position in the Solar System. Instead scientists think life could be microscopic or algae, or dependent on hydrothermal vents on an ocean floor similar to those found in the deepest parts of Earth’s oceans, so that they do not depend on the Sun. There may be life that depends on nitrogen or methane instead of oxygen.
Scientists have focused on terrestrial planets and moons in their search for life although some theories exists about life floating in the clouds of Jupiter and Venus that depend on thin clouds of water there.
Europa is considered to have a large underground ocean, as are Ganymede, Callisto (Jupiter Satellites), and Enceladus (Saturn). Enceladus spews geysers of water into space from its south polar region. Until scientists are able to understand the structure of these bodies and make observations nearer to them, observing or detecting signs if life underneath rock and icy surfaces will be difficult.
Titan (satellite of Saturn) possesses large lakes of methane. Until further exploration of the moon and understanding of its chemistry is found, it is unlikely to yield proof of past or present life.
Mars is a popular subject for speculation about life. A large ocean covers parts of the planet and there is recent evidence of some liquid flows on the surface. Probes and artificial satellites scan the planet looking for signs of underground activity. Probes sent have found water in soil samples (Phoenix Mission). The Viking Lander experiments that attempted to find evidence of microbes in the surface in the 1970s were inconclusive.
A meteorite fragment found in Antarctica caused headlines in the 1990s. It came from an impact on Mars and found its way to Earth. Bacteria-like structures were found in the rock but the results are inconclusive and controversial.
Some Astrobiologists believe that life may spread between planets or moons by comets or asteroids – a process called ‘panspermia’.