There are weird and wonderful creatures in the dark depths of our oceans, but Earth is not the only world in our Solar System to have oceans, and possibly strange life forms, too.
Some worlds have vast quantities of liquid water beneath ice crusts, and we may be exploring them in your lifetime. Others have oceans of liquid methane or other organic compounds. The many moons orbiting the giant planets Jupiter, Saturn and Neptune are all very different from each other, as we have seen by fly-bys of the Pioneer and Voyager spacecraft.
Galileo discovered four moons orbiting Jupiter, which you can see for yourself with a good pair of binoculars. Europa is one of them, and underneath a thick icy crust covered in cracks and ridges, it is thought to have a deep saltwater ocean. The sun is too far away to melt the ice, and it will be dark, but heat can come from tidal stresses and from a warm interior, as inside the Earth. NASA plans to launch the Europa Clipper in 2024, on a six-year voyage to investigate the conditions. Could there be life in those oceans?
One of Saturn’s moons, Enceladus, was visited by NASA’s Cassini missions. It photographed fountains or plumes of saltwater coming through fissures in its surface, probably warmed by thermal vents on its sea floor.
Another moon of Saturn, the giant Titan, is larger than the planet Mercury, and has lakes and seas of methane on its surface under a hazy atmosphere. Organic compounds may be forming and raining down – methane rain, but pools of water may be present too. It will be very exciting when (and if – keep your fingers crossed) a robot lander called Dragonfly, planned to launch in 2027, arrives on Titan. That is an 8-bladed quadcopter, a flying drone that can leap from one place to another. Unlike the tiny helicopter Ingenuity on Mars, Dragonfly can be much bigger since the atmosphere is thicker, and the gravity is less. For about three years Dragonfly will take images, study the weather, geography, and composition of samples at different sites. Its adventures will have to be pre-programmed since radio signals will take more than two hours to get there. The ingredients of life seem to be present – but did it get started?
Meanwhile the robot Perseverance continues roaming on Mars and peering under rocks.
Let’s look everywhere we can!