NASA has outlined what could be the next major phase in the search for life in our Solar System. Under the direction of the US Congress in 2016, the space agency's Planetary Science Division looked at the feasibility of placing a lander on Jupiter's moon Europa. Now a 21-member Science Definition Team has delivered a detailed report on what such a mission could look like and how it would directly seek out extra-terrestrial life for the first time since the Viking missions to Mars in the 1970s.
Life is one of the most difficult things to look for in space because the Earth is the only example we have of an inhabited planet. Once we leave the atmosphere, what life, if any, that might be found is still almost as much a matter of conjecture as it was in the 1950s. The difference is that today scientists benefit from a growing understanding of the biological sciences, the failure of Viking to find life on Mars, and our increasing knowledge of the nature of the other bodies in the Solar System.
Armed with this, the NASA team was able to provide a detailed 264-page report of what a Europa landing mission tasked with seeking out life would be like. Assumed to be launched in 2024, the mission would follow the planned Europa Flyby mission, fine tuning its requirements based on data gathered during its encounters with the moon.
If attempted, the landing would be the most ambitious ever. Jupiter is 457 million miles (735 million km) away and a radio signal would take 41 minutes to reach Europa. This means that the landing would need to be completely autonomous, yet able to land without parachutes on an airless moon that very little is actually known about and may have few suitable landing areas. In addition, it's a highly radioactive environment that's very hostile to electronics.
Despite this, NASA has some idea what such a mission would be like. It would be a 20 to 40 day mission, depending on when its 45 kWh primary batteries ran out. While there, the immobile lander would return images, collect samples and analyze them using a suite of instruments, including spectrometers and a microscope capable of identifying microbial cells.
The primary goal of the mission would be to look for direct signs of life – the first such since the two Viking landings on Mars in 1976. The lander would seek out direct evidence, including microbes, organic molecules, waste products, metabolic indicators, and other signs. According to NASA, the instruments available for the landing mission would be able to detect life at a level similar to what might be found in the subglacial Lake Vostok ice in Antarctica, which is eternally buried under 3,900 to 4,200 m (12,800 to 13,780 ft) of ice and as close as one can come to Europan conditions on Earth.
The second goal would be to determine how habitable Europa is by analyzing material from the surface, sampling non-ice surface minerals, and evaluating the proximity of water to the landing site in the form of water plumes, flooded fractures, and near-surface lakes or still pools. One point of particular interest will be to confirm if the sub-surface ocean is in contact with the moon's rocky core. Europa is one of only two moons in the Solar System suspected to have a subsurface global ocean that is in contact with the seafloor – making it Earthlike enough to warrant closer investigation and one of the highest priority targets in seeking life.
The final major goal will be to evaluate the surface and subsurface to support later landing missions by looking at the dynamics of the surface. In this way, NASA will be able to determine how to best set down larger spacecraft at a later date, and how to gain access to the subsurface ocean.
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