September 10, 2018

One planet in our solar system might be a little wetter than we previously thought. A team of Italian scientists recently found evidence that a lake of liquid water most likely exists on Mars, buried deep beneath the planet’s southern polar ice cap. The team published its findings on July 25, 2018, in the journal Science.

Italian scientists recently found evidence of what they believe to be a liquid water lake beneath the southern polar ice cap of Mars, the fourth planet from the sun. Credit: NASA/JPL/Malin Space Science Systems

Mars is a very cold place. On average, the surface of the planet is about -80 °F (-60 °C). As on Earth, however, the poles are even colder. Both poles of Mars feature permanent caps of water ice that are more than 1 mile (1.6 kilometers) thick. In addition, the southern cap has a roughly 25-foot (8-meter) thick permanent covering of frozen carbon dioxide. The northern cap has a diameter of about 625 miles (1,000 kilometers), and the southern cap has a diameter of about 220 miles (350 kilometers). In the Martian winter, the caps expand as layers of carbon dioxide frost condense from the atmosphere.

Images such as this one, showing curved depressions in Mars’s Utopia Planitia region, prompted the search for subterranean water with ground-penetrating radar. Credit: NASA/JPL-Caltech/Univ. of Arizona

The team of scientists analyzed data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), an instrument aboard the European Space Agency (ESA) probe Mars Express. Mars Express has been studying the surface of Mars since 2004. MARSIS is a ground-penetrating radar device. Ground-penetrating radar can detect underground features and objects beneath rock and ice. The radar waves reflect off liquid water, however, and for years MARSIS has returned many images with this tell-tale reflection beneath the planet’s south pole. At last, after ruling out other possibilities, the scientists concluded that the radar had found a triangular lake basin about 12 miles (19 kilometers) wide and 1 mile (1.6 kilometers) deep.

The Martian lake might be similar to Lake Vostok and other subglacial lakes on Earth. Lake Vostok, the largest lake in Antarctica, lies beneath 2.5 miles (4 kilometers) of ice, has been isolated for 35 million years, and has temperatures below the normal freezing point of water. But life still likely exists there. If life exists on Mars, it could likely be found in such subglacial lakes. The odds of finding life there are still long, however. The Martian lake would be dozens of degrees below the normal freezing point of water and filled with salts toxic to life on Earth.

As scientists pinch and probe Mars for life, they are also eager to search for life beneath other planetary ice in our solar system. Europa and Enceladus, moons of Jupiter and Saturn, have warm oceans beneath their icy exteriors, and present the best possible chances for extraterrestrial life. The search for life will involve drilling through ice, however, an incredibly complex task even here on Earth. Engineers will have to design a remotely operated drilling system that can withstand the stresses of launch, spaceflight, and landing; drill through massive layers of ice using only batteries or nuclear power; and capture, analyze, and return data to Earth—quite a list! The testing for such a drilling system will begin on our own planet’s subglacial lakes.

October 3, 2014

Up to half of the water in Earth’s oceans may be older than the sun and the rest of the solar system, including Earth itself, according to a new study. The findings indicate that Earth and other bodies in the solar system “inherited” their water—in the form of water ice—from interstellar space. The findings also suggest that if interstellar water ice survived the formation of the solar system, other planetary systems in our Milky Way Galaxy may also have had access to the single most important ingredient necessary for life as we know it.

The solar system is actually awash in water. Oceans make up about 70 percent of Earth’s surface. But water ice also exists in comets and on Jupiter’s moons Europa and Ganymede and on Saturn’s moon Titan. Mars has vast amounts of water ice at its polar regions, and the planet Mercury and Earth’s moon also have water ice within craters that are never fully exposed to the sun. Where did all this water and water ice came from? Scientists already knew that the clouds of gas and dust from which stars form contain water in the form of ice. But they weren’t sure whether water ice could survive that violent processes that occurred when the sun was born. Perhaps the radiation given off by the new sun vaporized most or all of the water ice or broke the water molecules into atoms of hydrogen and oxygen. In that case, the water in the solar system must have reformed in some way.

Stars are born from clouds of gas and dust that contain water in the form of ice.  (NASA)

To determine how much of the solar system’s water or water ice is “original,” the scientists created a computer model that mimicked conditions in the early solar system. In particular, they wanted to know whether the processes that led to the formation of the solar system could account for the amount of deuterium in Earth’s oceans and in comets and meteorites. Deuterium, an isotope (form) of hydrogen, is a key part of a kind of water called heavy water. The nucleus of an ordinary hydrogen atom consists of a single negatively charged particle called a proton. The nucleus of a deuterium atom consists of a proton and a single electrically neutron particle called a neutron. Deuterium forms only under certain circustances, in extremely cold environments, such as interstellar space, for example.

When the scientists ran the model, they discovered that radiation given off by the newly formed sun could not account for the deuterium in the solar system. In fact, they calculated that up to 50 percent of the water in Earth’s oceans comes from water ice that formed in interstellar space before the solar system even existed. As much as 70 percent of water in comets may have survived the transition from insterstellar space to the solar system.