Archive | June, 2016

Asteroids D.7.1

30 Jun

Asteroids in particular are the rocky leftovers from solar system formation. Most are small and because they’re not super massive, they generally come in a variety of shapes.

There is Vesta which is relatively rounded. Then there is a list of a number of other ones from Mathilde to Eros, showing that there’s not enough mass there for gravity to take over and turn the rock into a sphere.

So too small, but despite all their numbers, despite all their trillions, if you took all the asteroids in today, and added them all up, they would be less than what it would take to make a Mars, or to make a Moon, or something along those lines. So there’s not enough material there to make a planet – Currently.

Reaction to Comets and Asteroids D.6.30

29 Jun

Historically humans have always reacted to comets, to asteroids. But perhaps, more importantly is the fact that an impacting asteroid or comet can fundamentally change biological evolution on this planet.

Asteroids and comets are also important because they are the remnants of solar birth. They contain the original composition and the original material from the solar worlds, and we can catch some of that material in the form of meteorites coming down. And so we can learn to test what we think is happening with solar birth, both in terms of both our solar neighbourhood and exoplanets neighbourhoods, by taking a look at pristine material, or processed material from asteroids or meteorites.

Asteroid Belts D.6.29

28 Jun

What is the asteroid belt? And why are there meteorites?

Asteroids and comets might seem negligible in the big scheme of things because they’re relatively small compared to worlds that we’ve been examining like Mercury and the Moon, they’re a lot smaller.

But there is strength in numbers. And the trillions and trillions of comets and asteroids make them far more important than their small size and mass might initially indicate.  And for example, few objects in astronomy have the opportunity to impact our daily lives more than a comet and an asteroid does.

Enceladus D.6.28

28 Jun

Enceladus is a very interesting moon. It is sort of white with blue tiger stripes and methane fountains. The blue sparkling blue methane going on up is backlit by the Sun.

These ices, even though you’re farther out, those ices deform and they melt at much lower temperatures than rock.

But still, even this far out in the Solar System, it allows volcanism and tectonics to occur with ices. And these are little bits on the Jovian gems of fire, like Io, and ice, like Enceladus.

Titan D.6.27

26 Jun

Titan is really interesting. Titan has a very thick atmosphere. It has ongoing erosion. It is a sort of a yellowish, hazy ball. And if you look at wavelengths other than visible light, you can penetrate that haze, and what you see underneath is that there’s this striation. You get lighter areas and darker areas underneath. And if you drill down even more, what you find is that those darker areas may be oceans. A sequence of what appear to be lakes on Titan. And these are not lakes of water, these are perhaps oceans, these are lakes of hydrocarbons – In other words, lakes of gasoline and lakes of carbon fuel. So you could get on your boat, and you could pull your gasoline straight out of the lakes of Titan as you motor around.

Titan is a fascinating planet, with its hydrocarbon lakes to check out. A little farther out, at Neptune, we have Triton, which was apparently a captured moon of Triton. And it shows some very interesting active geological activity. Now it might be a little surprising that you go that far out in the solar system, where it’s quite cold, and yet you find active geological activity. Not from rocks but from methane, from ices, things along those lines. And even though it’s very cold, it’s not that cold relative to ices in other sorts of liquid like methane. And so you can drive very active geological processes by not having rocks, but by using ices and hydrogen compounds.

A frosty looking Triton and what looks like to be geysers of methane. And then the darker plume that they leave primarily on one side, indicating that Triton probably has some wind patterns that is blowing the geysers coming off from some of those plumes on Triton.

Callisto D.6.26

25 Jun

Callisto is the least geologically active of the Galilean satellites. Because its way farther out, it doesn’t get that tidal squeeze and release, squeeze, release effect going on.

It has no orbital resonances since it’s the farthest one out, and so it looks a bit more like the Moon or Mercury. It’s an older body, a bit more heavily cratered. But what is a little bit remarkable about Callisto is the relative difference between the very dark areas and the very light areas, where you see the impact craters have had. So you get almost this quite stark contrast between some sort of a very dark surface and a very white underneath.

Ganymede D.6.25

24 Jun

Ganymede may have a liquid ocean – water under its a little bit more cratered crust. It’s a little bit farther out so it’s not as tidally flexed, and so you don’t get as much erosion, active geological processes.

There is a bit more craters, a few older craters on the surface. But that surface also has a jumbled, crinkled iceberg looking effect. And so there may well be a deep liquid ocean under Ganymede.

Europa D.6.24

23 Jun

Europa, a little bit farther out in the system. It may have a very deep liquid ocean under its icy crust, due also to tidal heating. That tidal squeeze, release, squeeze, release is what keeps Europa warm, not as hot as Io, but warm. But also warm enough to support the idea that there may be liquid water under that icy surface.

Magnesium sulphate might be the major salt component, as opposed to Earth, where we have sodium chloride; regular table salt is what makes our oceans salty. On Europa it might be magnesium sulphate.

Elliptical orbit of Io D.6.23

22 Jun

How did Io get into an elliptical orbit? The elliptical orbit is caused by the orbital resonances with the other Galilean moons, so in particular Europa and Ganymede. And you know what an orbital resonance is. It just means that one planet goes around an integer multiple times of another planet. So in this example every time Ganymede, which is one of the farther ones out, goes around one orbit, which it completes in about seven days. So every time it does one of those, there’s an orbital resonance with Europa.

Europa will go around twice in the same amount of time, and Io will go around four times. So these are orbital resonances because they are exact integer multiples of one another. It’s not 4.2 or 3.8; it’s four because you have an integer relationship between the orbital periods. And it’s these orbital periods that give a little extra gravitational nudge, which then pushes Io into its elliptical orbit, which causes the tidal stressing from Jupiter, which causes the fantastic magma sulphur displays on Io.

Io D.6.22

21 Jun

The Galilean moons of Io, Europa, Ganymede, and Callisto are quite geologically active.

Io is the most volcanically active object in the solar system. It’s got this yellow colour and that yellow is from sulphur. There are lots of dark regions and there are red regions. And this is from volcanic plumes that come up, spew their material onto the surface. In some cases the magma erupts with such velocity that it can escape Io and then becomes part of Jupiter’s atmosphere, its magnetosphere. And so you get this very blotchy appearance from the hyperactive volcanic activity on Io. We’ve actually even been able to watch some of the volcanos erupt on Io.

We can actually watch, in real time, the surface of Io change due to its volcanism.

So, why does Io, it’s relatively small, why does it have such active volcanisms? Well, it’s primarily due to its interior being kept very hot from tidal heating from Jupiter. So Io goes around in an elliptical orbit around Jupiter, but Jupiter’s gravity is so strong that when Io is close the planet is a little bit deformed. And then as it gets farther away, it goes back into a more spherical shape.  And you know that if you take an object and you squeeze it and you squeeze it and you let it go, and you squeeze it, and you let it go, that the object heats up, right? You can do this with a ball on Earth. And the same thing happens with Io. And this constant stressing from the tidal effects of Jupiter is what keeps Io’s interior incredibly hot and sustaining that sulphur volcanism going on – on Io.