New findings support prospect of life on Jupiter’s moon Europa
Europa is the sixth closest moon of the planet Jupiter, and the smallest of its four Galilean satellites, but still one of the largest bodies in the Solar system. Slightly smaller than Earth’s Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System.
What makes Europa such an attractive place to look for life is the possibility that it has liquid water and volcanic activity. Liquid water is essential for life on earth and is the most probable solvent for life elsewhere. Volcanic activity provides some of the heat necessary to keep the water on Europa from freezing and could provide important dissolved chemicals needed by living organisms.
There is strong evidence that beneath Europa’s frozen exterior of ice lies an ocean of liquid water — one of the essential ingredients for all living organisms.
Many scientists believe that this vast subterranean sea could host living microorganisms similar in size and complexity to bacteria found on Earth. Others question whether a frozen moon with a surface temperature of 260 o F (170o C) can produce sources of energy useful for the basic chemical reactions necessary for life.
But a new report in the Jan. 27 issue of the journal Nature concludes that Europa does indeed contain plenty of biological fuels, thanks to billions of charged particles that constantly rain down from neighboring Jupiter.
This relentless bombarbment of radiation “should produce organic and oxidant molecules sufficient to fuel a substantial Europan biosphere.
On Earth, all organisms use carbon as a basic building block of life to construct everything from cells to DNA. Many organisms obtain their energy from carbon-based molecules like sugar, and some form of energy is required to free the carbon atoms from their chemical bonds.
Plants and algae use energy from sunlight to produce their own organic molecules out of carbon dioxide gas taken from the atmosphere or the ocean. The process is known as photosynthesis.
A likelier source of energy may come from fast-moving, charged particles that pound Europa from the atmosphere of Jupiter. Jupiter has the strongest magnetic field of any planet,” more than 10 times stronger than Earth’s. When protons, electrons and other particles from space get trapped in Jupiter’s magnetosphere, they are accelerated to extremely high velocities.
Europa’s orbital path around Jupiter lies deep within this powerful magnetic field, so it receives a continuous barrage of electrified particles or ions.
When these ions slam into the icy surface of the moon, chemical reactions are likely to occur, transforming frozen molecules of water and carbon dioxide into new organic compounds such as formaldehyde.
It turns out that one of the most common bacteria on Earth, Hyphomicrobium, survives on formaldehyde as its sole source of carbon, and study concludes that similar formaldehyde-feeding microbes could be alive and swimming in Europa’s subsurface ocean.
In addition to creating organic fuels, radiation from Jupiter also may drive chemical reactions that produce oxidants — molecules such as oxygen and hydrogen peroxide that can be used to burn formaldehyde and other carbon-based fuels.
The problem is that, if there is a liquid ocean on Europa, it’s hidden beneath an ice sheet about 50 to100 miles (80 to 170 km) thick. So if extraterrestrial creatures are going to feast on formaldehyde, there has to be a way to get that compound through the dense layer of ice and into the liquid sea below.
Recent photographs taken by NASA’s Galileo spacecraft reveal evidence of sudden melt-throughs in the ice that could allow oceanic microbes to come into quick contact with oxidants and organic food sources. The result could be a dramatic increase in population similar to “microbial blooms” that periodically occur in the Earth’s oceans. Study points out that Europa’s surface ice appears to get naturally recycled into the ocean every 10 million years — a process that would allow a very gradual delivery of life-giving molecules to any submerged organisms.
And just how many microbes might exist in Europa’s sea?
Theconservative estimate: one per cubic centimeter — a far cry from the hundreds of thousands of organisms that occupy each cubic centimeter of water on Earth.
Could life on our planet have its origins ?
We will probably have to wait for one or more additional missions to Jupiter and Europa to verify the presence of liquid water and life on Europa. The planning for these missions is just getting underway. Current plans call for the use of radar to identify possible ice-water and water-rock interfaces on Europa and for the return samples of the surface ice.
Europa’s distance from the Earth and Sun and its thick layer of ice will make exploration difficult. However, discovering life on Europa would double the number of planets we know of with endogenous life. Even if no evidence of life on Europa is found, its exploration would provide a wealth of information
about the chemistry and planetary physics of a very interesting body. Such information could help us better understand the atmospheric chemistry (with implications for global warming models), geophysics and other practical issues here on Earth.
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