The Genesis Planet

September 02, 2008

Bacon_eridaniA world dubbed the Genesis Planet was created in the 1982 Star Trek film “The Wrath of Khan.”

In the story, humans meddle with Mother Nature to transform a lifeless world into a paradise at a greatly accelerated pace from normal planetary evolution. Life, too, evolves at an accelerated pace. And so the Star Trek crew witnesses life unfolding before their very eyes. 

Although science fiction, there could be a Genesis Planet right in our galactic backyard, only 10 light-years away. The world orbits the southern star Epsilon Eridani, which is the third closest star to Earth viewable without a telescope, shining at third magnitude.  The planet is only 800 million years old -- too young for life to evolve into complex organisms, but the seeds of life could already be stirring.

I’m jumping the gun here because the planet in question is slightly more massive that Jupiter, made mostly of hydrogen, helium and trace amounts of methane, ammonia, and other elements. Like Jupiter, it has no solid surface.

But, it’s possible that the gas giant has a system of potentially habitable moons. For now, detecting such moons is vastly beyond our current telescopic capabilities.

Still, computer simulations predict that satellite birth is common around Jovian-like planets; moons can form from debris disk encircling the newborn planet. It’s sort of an HO model train version of much larger circumstellar disks that are the birthplaces for planets.

Eridani_palomar

Even though actual satellite systems whirling around our biggest gas giants -- Jupiter and Saturn -- are quite different, the total mass in both systems is about one hundredth of one percent (0.01 percent) of their respective parent planet's mass.  This could very well be a common moon-to-planet ratio among gas giants. 

Now, if most of the circumplanetary debris go into making one body, a moon as big as Mars could form around a Jupiter-sized planet.
 
What’s also intriguing is that the two largest gas giants in the solar system host a family of satellites that are chemically and geologically quite diverse.  There’s Jupiter’s volcanic moon Io, Europa with a likely subsurface ocean of water, as well as Saturn’s largest moon Titan with its dense and organic-rich atmosphere.

Titan has been compared to what Earth may have chemically looked like before life appeared nearly 4 billion years ago. The surface is coated in organic compounds, and it has a dense atmosphere of nitrogen.

It's even larger than Mercury, so the moon has a hydrological cycle of liquid methane and ethane rainfall that forms lakes and rivers. The lack of many craters indicates that Titan's surface may be relatively young due to Earth-like processes of tectonics, erosion, winds, and volcanism.

Galilean

The problem is that, at one billion miles from the Sun, Titan is a frigid place at nearly minus 300 degrees Fahrenheit. But if we could move Titan closer to the Sun, astrobiology could explode across the moon, much like Trek’s “Genesis Planet.”

This could be exactly what is happening for any hypothetical Titan-like world orbiting Epsilon Eridani’s giant planet. The world would be much warmer than Titan, and least for part of the planet’s seven-year orbit about the star.  This is greatly complicated by the fact that the planet is in a looping eccentric orbit that carries it as close to the star as Earth is from our sun, and as far as Jupiter is from the sun. 

What’s tantalizing is that the planet’s orbit carries it close to the star's habitable zone -- the region where temperatures are warm enough for liquid water to remain on the surface of a planet with an atmosphere.

Field_eridani

Because of the planet’s eccentric orbit, any satellites would experience long cold winters and brief hot summers. Still, a large moon might remain cozy for life over the long winter.

It could have a blanket of atmosphere thick enough to retain heat, especially if it contained greenhouse gasses such as carbon dioxide and methane.  The moon could have geothermal activity, or heat could also be induced by gravitational tidal pumping (as is the case with Jupiter’s moon Io and Saturn’s moon Enceladus).  Also, subterranean life on would not be as affected by the wild temperature swings.

When the Sun was 800 million years old, the very first primitive microorganisms may have begun populating the cooling Earth, and perhaps Mars too. A young, comparatively massive Titan-like moon could be a world where the first steps in the emergence of life are taking place right now.

This is probably the most compelling reason to identify and then ultimately explore, with artificially intelligent probes, the emerging biosphere of such a moon. The staggering technical challenges of interstellar spaceflight aside, such exploration could at last address one of the most fundamental questions in science: how does life begin in the universe?

Image Credits: G.Bacon/NASA, Caltech, A.Feild/NASA

about

Ray Villard writes on popular astronomy topics for magazines, radio shows and planetariums and is the news director for the Hubble Space Telescope.



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