Wonders of the Solar System

On the first day of winter (December 21), I saw the companion book to the Bluray set I have of Wonders of the Solar System at the library.  Yesterday, I decided to finally watch these disks.  I started with disk 2, episode 4 which was about Mars, Venus and Io.  Brian Cox explained simply, with two different sized rocks, how Mars is now dead because its surface area (for heat loss) is much larger in proportion to its volume than earth (click here for a spreadsheet).  Mars' core is now solid and the largest volcano in the solar system is now dead.  The solid core also meant the magnetic field that protects Mars' atmosphere is gone and this allows the solar wind to strip much of its atmosphere away (I suppose the thin atmosphere that is left is held there by gravity).  I found the part about Io to be the most interesting.  Three scientists (Stan Peale, Patrick Cassen, and R. T. Reynolds) had predicted that this moon closest to Jupiter and influenced by two other of Jupiter's moons would be a very active (volcanically) planet.  The regular tug-of-war on Io by Jupiter and the two other Galilean moons created the active volcanism on Io.  It was interesting how infrared spectroscopy is used to detect seasonal changes in methane on Mars and this is hypothesised evidence of extra-terrestrial life.

The fifth episode was about life on other planets.  Apparently, there is a 100 km deep ocean beneath the ice sheet covering Europa.  It is hypothesised that Europa is a likely candidate for extra-terrestrial archaea based upon observations of archaea in the ice of Iceland. Bacteria which digest H2S and excrete sulphuric acid are common in some hotspots on the earth.  The main point of this episode was to compare how life found in extreme conditions on earth can provide parallels for some places in the solar system.

The first episode was about the sun.  He talks about how the sun is 400 times farther from the earth than the moon and also 400 times bigger in diameter than the moon (click here for spreadsheet) and this is why we have perfect solar eclipses on occasion.  Not a coincidence I think (that's the Hand of God).  He goes over briefly the H-R diagram and sun spot activity that correlated with water flow in a South American river.  The importance of Earth's magnetic field in diverting the solar wind and channeling solar particles to the poles to create the northern lights is also covered.  Brian Cox describes how with a can of water and a watch, one can figure out that the sun gives off 1 kWatt/square metre on the surface of the earth "and that's why I love physics".

The second episode is about how the solar system formed and focuses on how Saturn and its rings and moons are a microcosm of how the solar system formed.  Cox uses his simple model to show how the ancients observed the retrograde pattern of Mars' motion in our night sky.  There is a lot of mention of how conservation of angular momentum is a fundamental law that applies to anything from the draining of water in a sink to tornadoes to the formation of the solar system.  I think this is why the outer planets orbit at a slower speed than the inner planets.  I like how Cox mentions he wrote to JPL and asked for the first photos from the Martian surface which were taken by Viking in 1955 (and he got them).  I remember, as a kid saving Edmonton Journal clippings of the launch of Voyager in 1977 and the old Radio Shack comic books they gave out which talked about the space age.  I had a copy of the 1979 comic book at one time which has a picture of Voyager I on the cover.

One of the interesting concepts described in the second episode was orbital resonance of Jupiter and Saturn when they line up together.  This was the reason for the Late Heavy Bombardment.