Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
Is there life beyond Earth, even in our Solar System? This mission might be humanity’s best hope of finding it.
The biggest question facing humanity might be, “Does life exists beyond Earth?”
When a planet transits in front of its parent star, some of the light is not only blocked, but if an atmosphere is present, filters through it, creating absorption or emission lines that a sophisticated-enough observatory could detect. If there are organic molecules or large amounts of molecular oxygen, we might be able to find that, too. It’s important that we consider not only the signatures of life we know of, but of possible life that we don’t find here on Earth. (ESA / DAVID SING)
Other solar systems might possess advanced or planet-altering biological activity, but simple life could exist right here.
Scanning electron microscope image at the sub-cellular level. While DNA is an incredibly complex, long molecule, it is made of the same building blocks (atoms) as everything else. To the best of our knowledge, the DNA structure that life is based on predates the fossil record. The longer and more complex a DNA molecule is, the more potential structures, functions, and proteins it can encode. (PUBLIC DOMAIN IMAGE BY DR. ERSKINE PALMER, USCDCP)
Among the moons in our Solar System, the largest are Ganymede and Titan (the only moons larger than a planet: Mercury), followed in size by Callisto, Io. the Moon, Europa, and Triton. Along with Pluto, Eris, the Sun and the major planets, these are the only worlds in the Solar System larger than 1,000 km in radius. (NASA, VIA WIKIMEDIA COMMONS USER BRICKTOP; EDITED BY WIKIMEDIA COMMONS USERS DEUAR, KFP, TOTOBAGGINS)
In this artist’s rendition, NASA’s Clipper spacecraft makes one of its many dozen close passes to Europa, the most likely candidate for life in the Jovian system to date. With all the ingredients it possesses and the conditions as we know them on this world, Europa might be the most life-friendly world beyond Earth presently known to humanity. (NASA/JPL-CALTECH)
All life:
harvests and metabolizes energy/resources,
responds to external stimuli,
grows and adapts,
and reproduces.
Acidobacteria, like the example shown here, are likely some of the first photosynthetic organisms of all. They have no internal structure or membranes, loose, free-floating DNA, and are anoxygenic: they do not produce oxygen from photosynthesis. These are prokaryotic organisms that are very similar to the primitive life found on Earth some ~2.5–3 billion years ago. (US DEPARTMENT OF ENERGY / PUBLIC DOMAIN)
While liquid oceans cover 70% of our surface, diminutive Europa has more water than planet Earth.
Based on the data collected by Galileo, the previous generation of NASA orbiter to study the Jovian system, we learned that Europa contains more water than all of planet Earth, combined, despite being much physically smaller and less massive in size. This water should exist in the liquid phase beneath the surface ice, providing a potential location for life to arise and thrive. (KEVIN HAND (JPL/CALTECH), JACK COOK (WOODS HOLE OCEANOGRAPHIC INSTITUTION), HOWARD PERLMAN (USGS))
Beneath a thick layer of water-ice, Europa’s interior experiences high pressures and temperatures.
Scientists are all but certain that Europa has an ocean underneath its icy surface, but they do not know how thick this ice might be. This artist concept illustrates two possible cut-away views through Europa’s ice shell. In both, heat escapes, possibly volcanically, from Europa’s rocky mantle and is carried upward by buoyant oceanic currents, but the details will be different and will lead to different observable signatures for the instruments aboard NASA’s Clipper. (NASA/JPL/MICHAEL CARROLL)
Nearby, massive Jupiter exerts tidal forces on Europa, heating its core while shearing and cracking its icy surface.
Europa, one of the solar system’s largest moons, orbits Jupiter. Beneath its frozen, icy surface, a liquid water of ocean is heated by tidal forces from Jupiter. Its properties are governed by its history and location in the Solar System. Even though it is large, massive, and may harbor life beneath its surface, its properties as a moon of Jupiter are what make it such an interesting candidate world for life. (NASA, JPL-CALTECH, SETI INSTITUTE, CYNTHIA PHILLIPS, MARTY VALENTI)
The internal heat melts Europa’s pressurized ice, creating a deep, liquid ocean.
This cutaway of Jupiter’s 4th largest moon, Europa. shows the internal core and rocky mantle, heated by the tidal forces exerted by Jupiter, surrounded by a large, thick layer of water. Beneath the icy surface, once the pressure and temperature reach a critical level, the water becomes liquid, meaning there must be an ocean beneath this icy crust. (KELVINSONG / WIKIMEDIA COMMONS)
Hydrothermal vents should line the seafloor: where energy gradients could enable life.
Deep under the sea, around hydrothermal vents, where no sunlight reaches, life still thrives on Earth. How to create life from non-life is one of the great open questions in science today, but if life can exist down here, perhaps undersea on Europa or Enceladus, there’s life, too. It will be more and better data, most likely collected and analyzed by experts, that will eventually determine the scientific answer to this mystery. (NOAA/PMEL VENTS PROGRAM)
In 2023, a new NASA mission — the Europa Clipper — will investigate Europa for biosignatures.
Europa’s crust is largely made up of blocks, which scientists think once broke apart, fragmented, and ‘rafted’ their way into their current configuration. As Europa also possesses a magnetic field, the geologic data strongly supports the idea that Europa contains a deep subsurface ocean, with the reddish-brown areas (in assigned colors) showcasing non-ice material that is thought to result from geologic activity. (NASA/GALILEO/JPL/UNIVERSITY OF ARIZONA)
NASA’s Clipper mission will undertake an orbital path that uses the gravitation of Jupiter and its other many moons to create a series of flybys that give global coverage of Europa under different seasonal and day/night conditions. Measuring time-variations in the results returned by the instruments will be crucial to uncovering all the potential bio-hints that Europa might have to offer. (NASA / JPL-CALTECH)
Dozens of flybys will reveal their compositions, temperatures, depths, salinities, time-variations, etc.
With life teeming beneath Earth’s Antarctic ices, Europa may be humanity’s best hope for discovering extraterrestrial life.
Scenes such as ice, stalactices, icebergs and liquid water are extrememly common in Antarctica. Sources of heat from beneath Earth’s surface create subsurface liquid water ‘lakes’ beneath the Antarctic ice, and living organisms exist and thrive in that environment. Perhaps, beneath the icy ocean of Europa, a similar story will emerge. (Delphine AURES/Gamma-Rapho via Getty Images)
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
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