Saturday, January 25 & Sunday, January 26, 2020
The abundance of water on Earth’s surface is a unique feature that distinguishes Earth from other planets and moons in the Solar System, and it has played a crucial role in the emergence of life on our planet. All known life needs water to survive, so finding water on other worlds is an important step toward searching for Earth-like life.
Worlds With Liquid
Earth’s interior remains active with a solid iron inner core, and a liquid outer core that generates the Earth’s magnetic field. A model for the formation of Earth’s atmosphere and oceans involves volcanic activity and outgassing from the interior. Water vapor from these sources condensed into oceans, augmented by water and ice from asteroids, protoplanets, and comets. In this model, atmospheric “greenhouse gases” kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity. By 3.5 billion years ago, Earth’s magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.
The top of the ocean probably lies beneath a 30-to-40-kilometer- (19-to-25 mile-) thick ice shelf. The ocean may be 10 kilometers (6.2 mi) deep at the south pole. Measurements of Enceladus’s “wobble” as it orbits Saturn suggests that the entire icy crust is detached from the rocky core and therefore that a global ocean is present beneath the surface. The amount of wobble implies that this global ocean is about 26 to 31 kilometers (16-19 miles) deep. For comparison, Earth’s ocean has an average depth of 3.7 kilometers.
Dione’s ice shell is thought to vary in thickness by less than 5%, with the thinnest areas at the poles, where tidal heating of the crust is greatest.
The findings by the Cassini team, together with the results of previous studies, hint that Titan’s ocean may lie no more than 100 kilometers (62 mi) below its surface. In 2014, NASA reported the ocean inside Titan may be as salty as the Dead Sea.
Worlds That May Have Had Liquid
The water has probably photodissociated and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venus is now the hottest planet in the Solar System, with a mean surface temperature of 735K (462°C; 863°F). The planet is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light.
Other scientists caution that these results have not been confirmed and point out that Martian climate models have not yet shown that the planet was warm enough in the past to support bodies of liquid water. Liquid water cannot currently exist on the surface of Mars due to low atmospheric pressure, which is less than 1% of the Earth’s, except at the lowest elevations for short periods. The two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 meters (36 ft). In 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.
Another Notable World
HAT-P-11b (or Kepler-3b) is an extrasolar planet orbiting the star HAT-P-11. It was discovered by the HATNet Project team in 2009 and is located approximately 123 light-years away. In 2014, NASA reported that HAT-P-11b is the first Neptune-sized exoplanet known to have a relatively cloud-free atmosphere and, as well, the first time that molecules, namely water vapor, of any kind have been found on such a relatively small exoplanet.
In 2002, this orbiter’s discovery of hydrogen just below the Martian surface prompted the creation of NASA’s Phoenix Mars Lander mission, which in 2008 confirmed theories that the element was contained in frozen water in Mars’s high-latitude regions.
Mars Reconnaissance Orbiter (MRO)
The MRO has sent back thousands of stunning images of the Martian surface that are helping scientists learn more about Mars, including the history of water flows on or near the planet’s surface.
Mars Science Laboratory Curiosity Rover
The InSight lander is the first outer space robotic explorer to study in-depth the crust, mantle and core of Mars.
Europa Lander: Potential Future Mission Concept art.
Europa Lander is a concept for a potential future mission that would look for signs of life in the icy surface material of Jupiter’s moon Europa.
JUpiter ICy moons Explorer (JUICE)
JUICE will spend at least three years making detailed observations of the giant gaseous planet Jupiter and three of its largest moons: Ganymede, Callisto and Europa.
The Mars 2020 rover will investigate a region of Mars where the ancient environment may have been favorable for microbial life, probing the Martian rocks for evidence of past life.
Dragonfly is an 8-bladed rotorcraft that will sample and examine dozens of sites around Saturn’s icy moon Titan in the search for the building blocks of life.
The Moon has fascinated humans since ancient history, but only since the mid-1900s have we had sufficient technology to launch a spacecraft to explore our closest neighbor. Learn more below about the history of human endeavors to reach the Moon, including the Apollo landings, present day orbiters, and future prospects that would help prepare for a possible lunar colony!