Water is essential to life on Earth. So, if we are searching for life off-world, it would make sense to look for signs of water. Astronomers have been doing exactly that: employing different methods to find the first signs of life outside of our own world. Until recently, it wasn’t known whether there is water anywhere else besides our home planet, let alone water in liquid form. Only with improved radar systems and satellites that travel beyond the moon have we finally found the water we were searching for.
Let’s start with perhaps the most exciting discovery: water on Mars. Recently, it was confirmed that our neighboring planet has an underground lake at the south polar ice cap about 12 miles across and 1 mile beneath the surface. This discovery is important because it’s the first persistent water we’ve found on another solar system body. The underground lake was found using a radar called MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding), and the image can be seen below.
MARSIS sent radio wave signals toward the center of the planet and examined the signals, or echoes, that bounced back, similar to bats using echolocation. The reflections from the lake’s water were stronger than the reflection signals on the surface of the planet, which allowed the astronomers to conclude that they had found water. This discovery was long awaited for. Liquid water beneath the martian ice caps was first hypothesized more than 30 years ago, and MARSIS had been hunting for water for more than 12 years.
Closer to home, we’ve also discovered water on both poles of our own moon. Using India’s Chandrayaan-1 spacecraft, scientists detected signs of water-ice using a range of instruments. Most notably, the Moon Mineralogy Mapper detected signs of a hydrogen-oxygen chemical bond, which tends to indicate the presence of water. Other instruments were able to measure the reflectivity of the moon’s surface and confirm that there are patches of water-ice, which are mostly concentrated in the shadows of craters.
Moving farther out in the Solar System, Saturn’s moon Enceladus doesn’t keep its water to itself. Instead, it spews out water vapor and icy particles in powerful jets. Not only does this make a gorgeous image, but these large streams in space also allow the Cassini spacecraft to fly through and sample the jets with two mass spectrometers. These jets contain water vapor, carbon dioxide, methane, salts and many more familiar particles flying at 800 miles per hour away from Enceladus. Further studies of Enceladus, which examined the gravity and wobble of its orbit, led scientists to believe this moon contains a global underground lake approximately the size of Lake Superior. This mineral rich water gives scientists hope that there may be microbial life lurking beneath the surface, although we’ll need a different mass spectrometer to determine that.
Of course, this isn’t all of the water in our solar system. Two of Jupiter’s moons, Callisto and Europa, both have subsurface oceans, the latter with more water than all of Earth. There’s even preliminary evidence of water vapor within Jupiter’s red spot. So, why did it seem like water in our Solar System is rare?
As we are finding, it’s not rare at all; water has been there for a few billion years, waiting for our technologies to improve and for our spacecraft to reach the outer planets. New radar technology is giving us the precision we need to confirm the presence of water, and future missions will be drilling down to directly sample the martian surface. Does this mean that we are close to finding extraterrestrial life? Not really. But, it looks more promising than before, with Enceladus leading the way. We will keep sending better technology into space to chase down these hopes.