Tuesday, May 25, 2010
Discovery: "Alien Moons" and "Alien Solar Systems" in "How the Universe Works"
“Alien Solar Systems” really focused on how our own solar system gradually became stable over billions of years. At one time, it had more than a hundred bodies in orbits like those of planets, but they coalesced into the current eight. Uranus and Neptune may at one time have been in reversed positions, and Uranus may have flipped over on its side because of a collision.
There is a slight risk that in some hundreds of millions of years, one planet could perturb the orbit of another, throwing it out of the solar system or toward the Sun. It’s even conceivable that this could happen with the Earth and Venus.
Mercury was hit by another body and lost its crust, resulting in the iron body it is today.
The film described the solar system of M star red dwarf Giese 581, which may have one or two “super earth” planets within the habitable zone (planet d has the best chance; here is the Wikipedia reference ). Planets near M stars orbit close and may often keep one side toward its sun, resulting in a “ringworld” effect around the edge of the sunny side where temperatures are moderate enough for life.
“Alien Moons”, the second hour, showed how the Moon was formed from a collision of a Mars-sized body with Earth.
The film also presented the case for the fact that several moons in our solar system could harbor life in under-crust oceans melted by gravitational tug. The best known is Europa (Jupiter), but so could Ganymede and Enceladus (Saturn). Titan (Saturn) has a hydrocarbon atmosphere, methane lakes and rains, and possibly an undercrust ocean, as does Triton (Neptune), which was actually a dwarf planet captured by Neptune and which may eventually fall into Neptune.
Several moons (most notably Titan) have organic compounds called “thiolins” on the surface or in subsurface oceans.
Here's an article (from "Age of the Sage") on Gliese 581 c (closer to the star) and a system diagram, link. Conceivably both c and d could have life, setting up a system like in the movie "Dune".
Wikipedia attribution link for image of super-earth Gliese 581 d.