Date: July 23, 2010

Title: Interesting Moons of our Solar System

Podcaster: Bollix!

Link: http://bollix.libsyn.com/

Description: A look at the Solar System’s more interesting and unusual moons, exploring the diverse nature and outright strangeness of planetary satelites.

Bio: The Bollix! Science and Skepticism Podcast is produced by Sam J Leonard and Josh Kelly and aims to explre the world of science and skepticism, bringing you the all latest in science, pseudoscience and special guests.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Bill Smith, from Mesa, Arizona. On the June 6th show, Greg Priestley challenged everyone who’s been enjoying this podcast to step up and sponsor a day. Today’s show is my response to that challenge. Now it’s your turn. Let’s fill all of the open sponsorship slots so that Pamela will never have to open another show with ‘This episode of 365 Days of Astronomy is sponsored by… no one.

Transcript:

Sam: Hi there, and welcome to the Bollix! Science and Skepticism Podcast for the 365 Days of Astronomy. I’m Sam Leonard…

Josh: And I’m Josh Kelly.

Sam: We’ve cleaned up our act and have decided to do some public service work for the wonderful 365 Days of Astronomy Podcast.

Sam: What’s coming up today?

Josh: Today we’re going to be discussing some of the weirdest and most wonderful bodies in the solar system-the moons.

Sam : The moons outnumber the planets themselves by a factor of greater than 10:1 and as a result there is a huge variety of exciting and unusual features out there to discover. In fact, each moon represents its own distinct world, some with their own complex weather systems and potentially even primitive living organisms.

Josh: The first of today’s moons under the spotlight is the aptly named giant, Titan- the largest of Saturn’s 61 currently known satellites.
(Titan weather report)

Sam: One of the first moons to be discovered by the great early astronomer Galileo Galilei is Io, the innermost of Jupiter’s four Galilean moons. Io is one of the most interesting and truly bizarre bodies in the Solar System and nowhere else in is as geologically active as this strange little world.

Josh: That is correct. Io is home to a staggering 400 active volcanoes which produce huge plumes of sulphur dioxide which can stretch for many hundreds of kilometres from the moon’s surface.

Sam: And many people have commented that being on the surface of Io would be akin to being in hell itself.

Josh: That is true.

Sam: Due to all the fire and brimstone.
This exceptional level of geological activity is due to the internal friction caused by immense tidal forces generated as Io is stretched, squeezed and strained between the colossal gravity of Jupiter and the other Galilean moons.

Josh: The moon has been scrutinised by several probes in the past decades and has returned numerous intriguing images. Perhaps the most well known and significant sets of images returned were a 1999 imaging by the Galileo probe and later by the New Horizons in 2007. Comparing the two sets of images demonstrates brand new features appearing on the surface of Io.

Sam: And 8 years in astronomical terms is such a short period that it is obvious that the surface and iron core of Io are in almost never ceasing flux, erupting and changing constantly. Perhaps the best thing about Io is its accessibility for the backyard astronomer. Even small telescopes can find and resolve a great image of Jupiter, and the Galilean moons including Io can be clearly seen as small orange blips spinning around the gas behemoth.

Josh: So from bizarre internal geology to bizarre shape, next on our list is Saturn’s Iapetus.

Sam: Indeed as Josh said, the shape of Iapetus really is nutty…..like a vast rocky walnut hurtling around the planet.

Josh: Iapetus is most recognisable for an unusual ridge running around the centre of this egg shaped oddity. However it is also famous amongst astronomers for its two-toned coloration.

Sam: The equatorial ridge may have originated when a small ring system similar to that of its parent planet plummeted into Iapetus. This, coupled with the strange dark on one half and bright on the other colouring, make this moon one to be seen to be believed. Iapetus is also noteworthy for its gaping craters and it has clearly been slammed by space debris for millennia.

Josh: So we’ve discussed the physical and chemical but no podcast on space would be complete without even a brief mention of the biological and the astronomical holy grail- the possibility of extra-terrestrial life. A number of moons currently represent our best hopes for finding life in our Solar System.

Sam: Considering the potential for finding extra-terrestrial life on one of the moons is obviously a numbers game. Each moon represents a distinct world with wildly different structures, weather and chemistry, offering more opportunities for life to evolve. Titan and Europa have previously been identified as strong candidates for harbouring ET life but Saturn’s sixth largest, Enceladus has been widely described as the “best bet for life”.

Josh: Like Io, Enceladus is also geologically active and has been observed ejecting material in crests far above the surface. These plumes of ice and liquid contain sodium salt and are highly suggestive of the presence of a liquid water ocean under the surface.

Sam: The possibility of liquid water being present in abundance is an exciting prospect for all people, particularly astrobiologists whose work thus far has sadly not been as busy as it might soon be. The distance from the Sun means that Enceladus receives very little warmth and is superficially something of a Hoth. As with Io, the tidal forces at play cause frictional heating, and although the moon may not lie in what is traditionally thought be the “goldilocks zone” this may create its own central heating system for any life which may be present.

Josh: Jupiter’s Europa may have a similar structure to Enceladus with a thick icy surface covering a watery ocean. Subject to heat generated within the core, microbial life may also subsist in submarine vents close to the core as on earth.

Sam: Unfortunately we only have enough for one more moon today and we’re going to be taking a look at a satellite that can only be described as being slightly…backward. That’s right, we’re looking at the largest moon of Neptune, Triton, the only significantly sized moon in the Solar System to follow a retrograde orbit.

Josh: Retrograde orbit means that the moon orbits in the opposite direction to that of its parent planet, the ice giant Neptune. It has been suggested that one of Saturn’s famous rings, the Phoebe ring is formed and maintained by particles blasted off of the surface of Phoebe by micro-meteoroid impact.

Sam: The difference between Triton and smaller moons such as Phoebe however is its size. Obviously. Triton’s retrograde or “irregular” orbit is unique for an object of its mass. The orbit of a satellite is governed by how it becomes gravitationally associated with a planet. If a moon is formed during the formation of the planet, it will almost always become trapped in the increasing gravity of that planet and thus follow the direction of its orbit, following the principle of conservation of angular momentum.

Triton’s irregular orbit suggests a different origin. It seems likely that Triton originated as a separate object, with no relationship with Neptune. Over time the moon may have approached Neptune, from a direction and angle such that it would not be dragged into a regular orbit.

Josh: Another interesting fact about Triton is its future. Tritons orbit is slowly decaying and over time will soon pass Neptune’s Roche Limit.

Sam: Simply stated, the Roche Limit describes the distance from an object a body may pass before the tidal forces of the larger body’s gravity will cause disintegration of the smaller. Simple.

Josh: The decaying orbit of Triton means that within 3-4 billion years Triton will break apart and possibly cause the formation of a ring around the planet.

Sam: So, unfortunately we have run out of time for today’s podcast, we only have a 10 minute limit, hope you’ve enjoyed it and learnt something. For more astronomy and general science and skepticism ramblings, go to the Bollix! Science and Skepticism Podcast, which is suitable for everyone, except children.

Josh: Except the kids, yeah.

Sam: So thank you for listening and goodnight.

End of podcast:

365 Days of Astronomy
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