Europa
Discoveries of ICEBURGES on the surface give hope of finding life!
This recent discovery has made NASA think if they would not bother to go to Mars but go to Europa instead but untill they make up there minds everything is uncertain. |
Europa Facts
Discovery: Jan 7, 1610 by Galileo Galilei
Diameter (km): 3,138
Mass (kg): 4.8e22 kg
Mass (Earth = 1) 0.0083021
Surface Gravity (Earth = 1): 0.135
Mean Distance from Jupiter (km): 670,900
Mean Distance From Jupiter (Rj): 9.5
Mean Distance from Sun (AU): 5.203
Orbital period (days): 3.551181
Rotational period (days): 3.551181
Density (gm/cm³) 3.01
Orbit Eccentricity: 0.009
Orbit Inclination (degrees): 0.470
Orbit Speed (km/sec): 13.74
Escape velocity (km/sec): 2.02
Visual Albedo: 0.64
Surface Composition: Water Ice
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Europa Information
E uropa, fourth largest satellite of Jupiter, has gained the rank of one of the highest priority targets for an outer Solar System exploration mission. If liquid water were to exist on Europa, it would not be unreasonable to speculate on the existence of life there, perhaps forming near undersea volcanic vents. Life on Earth has been discovered at great ocean depths, beyond the penetration of sunlight, thriving on upwelling chemical nutrients from the interior of the planet. (see "The Greening of Europa," from Scientific Americanand "Clues to possible life on Europa may lie buried in Antarctic ice" from the Marshall Space Flight Center.)
NASA's Galileo spacecraft has recently sent back to Earth amazingly detailed images of the surface of Europa. Many scientists believe the pictures reveal a relatively young surface of ice, possibly only about 1 km (~3250 feet) thick in places. Internal heating on Europa due to Jupiter's tidal pull could melt the underside of the icepack, forming an ocean of liquid water underneath the surface.
More Images of Europa from the Galileospacecraft
As part of NASA's Outer Planets/Solar Probe Project, preliminary development has begun on a mission to send a spacecraft to Europa to measure the thickness of the surface ice and to detect an underlying liquid ocean if it exists. Using an instrument called a radar sounderto bounce radio waves through the ice, the Europa Orbiter sciencecraft would be able to detect an ice-water interface, perhaps as little as 1 km below the surface. Other instruments would reveal details of the surface and interior processes. This mission would be a precursor to lander missions, which would make detailed studies of the surface characteristics, such as composition, seismology, and physical state. Such landers might themselves be precursors to sending "hydrobots" or remote controlled submarines that could melt through the ice and explore the undersea realm.
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Here is some science fiction written by a NASA scientist about what Europa may turn out to be.
! ASTRONOMY
THE GREENING
OF EUROPA
Are the satellites of giant
planets a place to look for life?
In Arthur C. Clarke's new book 3001 (the third sequel to 2001), he envisions Jupiter's large moon Europa as the home to a diversity of life-forms that evolved around hydrothermal vents deep beneath Europa's global ice sheet. Clarke's writing, though fiction, builds on a very real sense of excitement in the scientific community: images from the Galileo spacecraft hint that liquid water--one of the necessities for the life that we know--may lurk below Europa's surface.
More than a decade ago the Voyager spacecraft revealed Europa as an unusual world: swathed in ice, marked by a network of mysterious brownish lines, and geologically young. Last December 19, Galileo whizzed just 692 kilometers (430 miles) above the surface of the satellite; the resulting snapshots capture a dynamic topography marked by formations that "appear to be remnants of ice volcanoes or geysers," reasons Ronald Greely of Arizona State University.
These discoveries provide insight into the amount of heat trapped inside Europa. Its surface temperature averages a chilly -200 degrees Celsius. Gravitational interactions among Jupiter's moons transfer energy to Europa's interior, however. If the energy flow is great enough, it might be sufficient to melt the underlying layers of ice, creating a vast ocean. The Galileo images show that "there was enough heat to drive flows on the surface," Greely reports, although they do not yet prove the presence of liquid water below.
The heightened interest in Europa comes at a time when scientists are increasingly considering the possibility that satellites, not just planets, might support conditions suitable for life. Within the past two years, astronomers have discovered possible planets circling eight sunlike stars. These giant worlds probably offer poor prospects for terrestrial-type biologies. But in a recent paper in Nature, Darren M. Williams, James F. Kasting and Richard A. Wade of Pennsylvania State University suggested that possible large moons orbiting two of the planets might fall into the "habitable zone" where life can arise.
The analysis is highly speculative, the Penn State authors admit. Nobody knows whether the newfound planets have any satellites at all, nor is it clear how likely it is that even giant planets will have satellites massive enough to hold on to a substantial atmosphere and to generate a protective magnetic field. On the other hand, the example of Europa suggests that there is some flexibility in the rules for habitability.
Indeed, common notions regarding habitable zones may be grossly conservative, argues Christopher F. Chyba of the University of Arizona in a commentary accompanying the Nature paper. Williams and his colleagues focused on environments that could allow liquid water and solid surfaces. But Chyba recalls that the late Carl Sagan envisioned life-forms that could thrive among the clouds of Jupiter; in the other direction, Thomas Gold of Cornell University suggests that simple organisms may thrive deep in the earth's interior. "It shows how little we understand life even on our own planet," Chyba reflects.
If Europa does have a buried ocean, does it contain life? Chyba responds with another question: "Can an ocean of liquid water persist for 4.5 billion years and not have life in it?" he asks. But a couple dozen kilometers of ice would pose a formidable barrier to direct contact between us and any possible them--a sobering reminder that we are still absolute beginners at exploring the worlds around us
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