Mysteries of the solar system

Astronomy Cast did a two part series each about mysteries of the solar system, the galaxy and the universe about a year and a half ago and I'm just now . It was way too much to absorb in a podcast so I'm going to try to recount all of them here. All information originated from their site or links provided by them.

First, the solar system.

1.) The Pioneer Anomaly: the Pioneer spacecraft (10 and 11) are heading towards the edges of our solar system but not at the speed they are expected to travel, they seem to be slowing down. The data has been difficult to analyze because some of the tapes have been misplaced and the the data was never intended to be analyzed this way. And the explanation is really....mathy. But it points to a possible significant misunderstanding on our part of the laws of physics. The Planetary Society is in the process of doing the largest analysis ever of 30 years worth of data.

2.) Axial tilts of Uranus and Venus: the Earth is tilted at 23.5 degrees. Uranus is tilted at 98 degrees when compared with the orbital plane of the sun (people sometimes ask tilted in comparison to what? There's your answer.) Whereas other planets can be thought of as tops spinning around the sun, Universe Today says Uranus is more like a rolling ball. The common wisdom these days is something big smacked into Uranus to flip it over on its side where it couldn't get up, like my dog sometimes.

For Venus, the tilt is a whopping 177.3 degrees. This means it's essentially upside down. This is why it rotates backwards (or clockwise when seen from above) as compared to all other planets in the solar system. The upshot of the almost upside down tilt is that the net difference versus the plane of the ecliptic is only 2.7 degrees so no seasons. Why is Venus jacked up? It could be caused by some asteroidal bombardments in the days of the early solar system. Key word to understand: Kirkwood Gaps.

3.) What's beneath Europa's ice? Io takes more pounding from Jupiter's immense gravity. Europa, which is one of the brightest objects in the solar system due to reflection, might have a warm, salty ocean under its icy crust if the probe data is correct. The hope is there's life under there.BTW, here's an acronym for remembering the names and positions of the Galilean moons in order from furthest in: I Eat Green Cows.

4.) Methane on Mars: the question is where is it coming from and how is it getting replenished. Due to the conditions on Mars, Methane only lasts a few hundred years. Is it geological activity or is it, again, life? If it's geological activity, it means Mars is not, as we've thought, geologically dead. Or maybe it's coming from meteorites.

5.) Titan's atmosphere: another question of, for one, where is the Methane that makes up less than 2% of the atmosphere coming from. It seems to be coming from a phenomenon known as cryovolcanism. It's also fascinating because it's a little moon with an atmosphere about 1.5 times the size of our own.

6.) Corona temperature: the corona is where the solar winds originate. It refers to the area around one million kilometers from the surface. Temperatures reach one million degrees. But the surface is only 5000 degrees. Why is the corona so hot and what is making it so hot? The preliminary answer involves magnetic field lines.

7.) The Kuiper Cliff: the Kuiper Belt starts sooner than I realized, within the orbit of Neptune. The prediction basically is that the further out you go, the more objects you should find. Instead, there is a sharp drop-off around 50 au's. What this means, according to a dude named Patryk Lykawka, is that there could be another planet out there sweeping its orbital path clean.

8.) Why are there long period comets: these are comets that have periods ranging from 200 to 10 million years. This means their orbits are very long ellipses. This could mean there's a planet in the area of the Oort Cloud that is periodically knocking objects loose into these crazy orbits. This does not mean that Planet X will return from the fifth dimension to destroy the world in 2012 like the Mayans thought. Another cool tidbit: the Oort Cloud isn't definitely proven but we can see what looks like it's "shadow" in the CMB. Cool.

9.) The geysers of Enceladus: Cassini has confirmed there are geysers ejected regularly from the South Pole region of Enceladus, one of Saturn's moons. And the geysers are of water and ice which means that maybe there's a warm ocean underneath somewhere. These geysers appear to be replenishing Saturn's rings. And Enceladus appears to just be an icy moon, like so many others. Why is it the only one (we know of) doing this weird thing?

10.) The Saturn Hexagon: another Cassini discovery, or rather confirmation since it was first seen by Voyager. There appears to be a perfectly shaped hexagonal hurricane on Saturn's north pole turning at the same speed the planet is rotating. A giant planetary hurricane is cool but not unheard of. But physics says it should be a circle. And by giant, I mean really giant. The sides are 14,000 kilometers.

The video is said to be quite amazing but...well it's all relative isn't it? It's amazing we can even get video from Cassini. Anyways, here it is.