Weeks after announcing that it has discovered planets in a distant solar system that could host life, NASA made another major announcement on Thursday – life beyond Earth can be supported in our own solar system, on the moons of Saturn and Jupiter. According to NASA researchers, Jupiter’s fourth-largest moon Europa and Saturn’s sixth-largest moon Enceladus have the potential to play host to life as we know it, as they may have the necessary ingredients required.
The findings come courtesy the Cassini-Huygens unmanned spacecraft and the Hubble Telescope. Cassini-Huygens was sent in 1997 to study Saturn, its rings, and its moon; while the Huygens lander was sent to the surface of Saturn’s moon Titan, the Cassini craft continued its journey to the planet’s rings and moons. Entering the Saturn orbit in 2004, the spacecraft has sent back a lot of data over the past 13 years to Earth, but the findings related to Enceladus might be the most important as they suggest the possibility of life on the small moon. The Hubble Telescope, on the other hand, has spotted plumes that may suggest liquid water on Europa.
Nasa's Cassini Returns High-Quality Images of Saturn's Moon Enceladus
The three key ingredients of life as we know are liquid water, a source of energy for metabolism, and chemicals such as carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur. Finding planets and other celestial bodies that have these elements in the right composition has been a challenge, more so in our solar system, but it seems NASA has finally achieved a major milestone in the process of determining if life can exist outside Earth.
Here are 10 things you should know about the new NASA announcement:
- Saturn’s Enceladus as a higher likelihood of being a host to life than Jupiter's Europa as it appears to have a form of chemical energy on which life forms can feed. Enceladus is a small, icy moon “a billion miles farther from the Sun than Earth” where the Cassini mission has found an abundance of hydrogen molecules in water plumes. Scientists have determined that 98 percent of the gas in the plume is water, roughly 1 percent is hydrogen, and remaining is a mixture of molecules of carbon dioxide, methane, and ammonia.
- Enceladus has an icy surface with oceans of water underneath, and scientists believe that the hydrogen originates from a hydrothermal reaction between the ocean and the moon’s rocky core. The Cassini scientists say if that is indeed the case, methane – a critical ingredient for life – can be present in the oceans as well.
- The life forms, if they exist or can exist, are likely to be microbial. Scientists are hopeful of finding the potential for life there because microbes flourish on Earth in hot cracks on the ocean floors, where sunlight cannot penetrate, using the same chemical reactions. In fact, the earliest life on Earth is thought to have taken such form.
- Microbes would be able to use the process of methanogenesis, in which hydrogen is combined with carbon dioxide dissolved in the water, to obtain energy. This process creates methane as a byproduct; methane is found in abundance on the Earth.
- However, Cassini – which is not equipped to find signs of life forms in the Enceladus plume because the plume had not been discovered until after the craft entered the Saturn orbit – has not found phosphorus and sulphur on Enceladus’s ocean. Scientists still suspect them to be present though, since the chemical composition of core of the moon is thought to be similar to meteorites containing the two elements.
- Hunter Waite, lead author of the Cassini study, said "Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes."
- On Jupiter’s moon Europa, Hubble’s Space Telescope Imaging Spectrograph (STIS) spotted plumes in ultraviolet light at the same location in 2014 and 2016. Scientists are still in the process of monitoring Europa to determine the frequency with which the plumes appear.
- Europa’s newly-imaged plume rises approximately 62 miles (or 100 kilometres) above the surface, while the one captured in 2014 was estimated to be 30 miles (roughly 50 kilometres) high. The warm region, considered a thermal anomaly on the icy Europa, close to the plume was seen in the late 1990s by the Galileo spacecraft.
- If the plumes and warm spots are linked, scientists say that the water escaping the icy surface would keep the surrounding areas warm. Another school of thought is that if the water from plume returns to the surface as a fine mist, it could be changing the surface grains and enabling them to retain heat longer than the surrounding landscape.
- The Cassini and Hubble findings have set the base for NASA’s Europa Clipper mission, which is planned to launch in the 2020s. In fact, the Hubble team plans to send a powerful ultraviolet camera with the Clipper mission; this camera would take images of Europa similar to Hubble’s but from thousands of times closer.
How scientists think water interacts with rock at the bottom of the ocean of Enceladus, producing hydrogen gas
Photo Credit: NASA
With these findings, Enceladus has become the prime candidate for finding life outside Earth, while Europa is another strong contender that requires further exploration.