Great Lake of Europa
INTRODUCTION –SEARCHING FOR LIFE BEYOND EARTH
A large liquid lake has been discovered just below Europa’s icy shell may provide a habitat for life.
Europa’s icy surface, as viewed from NASA’s Galileo spacecraft. Visible are plains of bright ice, jumbled cracks an indication of a sub-surface heat source that run to the horizon, and dark patches that likely contain both ice and dirt. CREDIT: NASA/Ted Stryk
HOW HAVE SCIENTISTS DETERMINED THE EXISTENCE OF THESE LAKES ON EUROPA?
- New research studies show Jupiter’s moon could have numerous large lakes just beneath its icy shell, and consequently closer to energy from the Sun, potentially providing a habitat for life.
JUPITER’S ICY MOON EUROPA IN BRIEF
- Europa is one of the four Galilean moons of Jupiter which has at least 63 moons in total including Europa
- Europa is slightly smaller than Earth’s moon and orbits Jupiter every 3.5 days. It has an iron core, a rocky mantle (shell), a radius of 1,569 km and it is 670,900 km distant from Jupiter.
- Although Europa is about 500 million miles away from earth it comes closer to resembling our planet and providing potential for life than anything else in the solar system
- There is a large, subsurface ocean of salty water deep beneath its frozen, ice pack crust thought to be in some areas tens of kilometers thick.
- Recently discovered lakes appear to be embedded closer to the surface.
- Europa has more water than all the oceans of Earth
EUROPA’S GREAT LAKE
- New research: A large liquid lake discovered approximately just 1.5 miles (3km) below Europa’s icy shell. Estimated to be equal in volume to all the North American Great Lakes combined.
- Europa could have numerous large shallow lakes just beneath its icy shell placing them closer to energy from the Sun.
One such lake lies underneath Thera Macula, one of Europa’s chaos terrains. Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain.
CREDIT: Paul Schenk/NASA
- Research also explains how nutrients and energy could get from the moon’s surface to its buried ocean.
- In doing so they could possibly provide a habitat for life which would be a key finding in the search for places where life might exist beyond Earth.
Europa’s "Great Lake." Scientists speculate many more exist throughout the shallow regions of the moon’s icy shell.
CREDIT: Britney Schmidt/Dead Pixel VFX/Univ. of Texas at Austin
HABITAT FOR LIFE
Scientists believe that
- The interaction between the Europa ice pack and the subsurface bodies of water transfer nutrients and energy that may lead to life existing under the Europa surface.
- Life in the oceans of Europa would be similar to that which exists deep beneath the oceans on Earth where light does not penetrate.
- Liquid water is thought to be necessary for life,
- Microbial organisms may survive in this buried sea.
The “lake” holds potential as a habitat for life, and there may be many more such lakes throughout the shallower regions of Europa’s shell, said lead author Britney Scmhidt, postdoctoral fellow at the Institute for Geophysics.
“The potential for exchange of material between the surface and subsurface is a big key for astrobiology. Europa’s subsurface harbours much of what we believe is necessary for life but chemical nutrients found at the surface are likely vital for driving biology.”~Wes Patterson, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. and a co-author of the study.
“Now we see evidence that it’s a thick ice shell that can mix vigorously, and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable. The material cycled into the ocean via these lakes may make Europa’s ocean even more habitable than previously imagined. The lakes may even be habitats themselves."~Britney Schmidt, lead author.
CHAOS TERRAIN ON EUROPA POINTS TO SUBSURFACE LAKES
Determining the existence of such a body of water
Chaos terrain on Europa points to subsurface lakes. (NASA/JPL/Ted Stryk)
- Europa’s surface is cold, around minus 170 degree Celsius (minus 100 K). The bottom of the ice is slightly warmer.
- Two circular bumpy features on Europa’s surface called "chaos terrains." similar to features on Earth suggest that Europa is still geologically active heated likely by tidal forces. These tidal forces provide more heat on Europa than would normally be the case for a celestial body that far away from the sun.
- That means plumes of warm water well up against the Europa ice cap, fracturing them, to churn the ice and subsurface water causing the "chaos" terrain features.
WHAT DOES THIS MEAN FOR THE POSSIBILITY OF LIFE ON EUROPA?
Nutrients and energy are transferred from the frozen surface to the vast ocean below resulting in the possibility that environments suitable for life could exist under the Europa surface. Life in the oceans of Europa would be similar to that which exists deep beneath the oceans on Earth where light does not penetrate. This could also mean that Europa is more likely to harbour extra-terrestrial life than Mars.
"On Earth, it is the volcano [melting the ice]. On Europa, it is the warm ice plume coming up from below” ~Schmidt
"You and I might not notice the difference, but geologically it’s very different. Heat melts some of the ice into enormous lakes beneath the crust. Think of Europa as one giant ice shelf floating on a global ocean, with a really rocky core.” ~ Paul Schenk, of the Lunar and Planetary Institute in Houston.
The icy moon Europa rising above Jupiter’s cloud tops. The picture was one of a handful of the Jupiter system that New Horizons took primarily for artistic, rather than scientific, value.
CREDIT: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
CONFIRMATION? – the next step in confirming liquid water under Europa?
- Confirmation of the existence of these lakes will involve a thorough investigation of both above and below the icy surface of Europa meaning a future mission to Europa is essential. The National Research Council’s Planetary Science Decadal Survey gave such missions one of the highest priority ratings.
FUTURE EUROPA EXPLORATION MISSIONS PROPOSALS
A joint NASA/EUROPEAN SPACE STATION SPACE mission to Europa known as the EUROPA JUPITER SYSTEM MISSION is being considered. The intention being that the EUROPA ORBITER probe, which is estimated to launch in 2020 arriving in orbit off Europa in 2028 will by remote study hopefully give clues as to how the ice layers and the subsurface ocean interact. It will also study the organic exchange between them which could result in the existence of microscopic life in the subsurface ocean and lakes.
The EUROPA ICEPICK MISSION would involve the drilling through of Europa’s ice pack and a unique opportunity to explore the subsurface ocean, in the hope of finding some form of life and also other valuable scientific data.
"Europa is likely to have a deep ocean of liquid water beneath its icy crust, making it an object of enormous interest as a possible abode for life," ~Planetary scientist Steve Squyres, with Cornell University
Funding for such missions to Europa is very uncertain. Most likely the Europa landers would cost anything from $800 million to $2 billion and that is only a rough estimate. This would involve input from several nations in order to obtain the necessary funding to make any one of these missions a reality.