Astronomy on Titan: Visiting the Solar System

After getting into orbit around Titan, let us what we need to do to visit the rest of the Saturn system, and also the rest of the Solar System.

Where we left off, we were in an orbit with an altitude of about 1000 km, not much less than Titan’s radius. We travel at 1.4 km/s relative to Titan with a period of 4 hours. To escape from that orbit, we need about 2.0 km/s or only 0.7 km/s more. So we won’t need much rocket fuel for that.

Let’s now consider going to Iapetus. That moon is 2.9 times as far as Titan from Saturn, and while Titan orbits at 5.56 km/s, Iapetus orbits at 3.26 km/s. So if one slowly spirals outward over several orbits, one will need a delta-V of 2.3 km/s. If one uses a fast “Hohmann transfer orbit”, one will need only 2.15 km/s and take about 22 (Earth) days to get there. Once one gets there, it will be easy to land, since its escape velocity is about 0.6 km/s.

Hyperion should be even easier, but the inner moons, Saturn’s rings, and Saturn itself will present some big challenges.

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Astronomy on Titan: Departing from There

Having looked at how to observe the Universe from Titan, I will consider how to depart from Titan and visit the rest of the Universe.

The first step in such a journey is to depart from Titan’s surface and go into orbit around that moon. Titan has a thick atmosphere and a low surface gravity, factors that act in opposite directions. Also, a low orbit would have an altitude of about 1000 km. Putting the factors together and doing some hand-waving estimates, I estimate a velocity change of about 2.3 km/s, compared to the Moon’s 2.0 km/s and the Earth’s 9.4 km/s.

Let’s see how much rocket fuel that one needs, how much mass of fuel for mass of payload, what one wants to get into orbit.

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Astronomy on Titan: Outside Visible Light

Outside of visible light, a good way to observe the rest of the Universe is with infrared light. Titan’s atmosphere is relatively transparent to some infrared wavelength bands, as can be seen from Cassini-spacecraft pictures like the one inlined here: Cassini: Mission to Saturn: Peering Through Titan’s Haze. It shows a false-color picture of Titan in 1.3, 2.0, and 5.0 microns wavelength, and one can easily see surface details.

So with infrared observations, one can do much of the astronomy that I’d described earlier without leaving Titan’s surface.

Radio observations open up some additional possibilities.

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Astronomy on Titan: the Solar System and Beyond

When the Sun gets eclipsed, one can observe four objects near it: Mercury, Venus, the Earth, and Mars. Over an eclipse system, one can observe them go back and forth around the Sun, evidently orbiting it.

Moving about as fast as the Sun, and looking like a bright star, would be Jupiter. It would get as far as 33d from the Sun, making it easier to see than the inner planets.

Looking with a telescope will reveal the Earth’s moon and Jupiter’s four big moons. One will quickly find that those four moons follow Kepler’s third law. As to the inner planets, Jupiter, and Saturn, if their motions are referred to the stars, then they will also obey that law. So we notice these sets of objects all obeying it:

  • Saturn’s moons
  • Jupiter’s moons
  • The Sun’s “moons”

So if one wasn’t sure of Kepler’s third law before, one would be sure of it now.

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Astronomy on Titan: the Saturn system

So once we are floating in a balloon atop Titan’s haze, we will get to see lots of interesting things. I will start with the Saturn system.

Saturn is an obvious place to start, because of its prominence. Its angular size is about that of a fist at arm’s length, much greater than anything else that one will see in its system. We will be able to see its atmospheric zones and belts, and near its poles, its auroras. We will also notice that it is flattened at the poles, with its flattening being about 1/10.

Saturn’s rings will also be visible, though even at their best visibility, they will be very close to being edge-on, and one may need a telescope to resolve them.

Several of Saturn’s moons will be visible to the unaided eye, and one will also see some of them being eclipsed by Saturn and some of them casting shadows on Saturn. It will take a telescope to resolve them, with only Rhea being even borderline resolvable without a telescope.

There are lots of interesting things that one can discover by observing them.

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Astronomy on Titan: Looking Upward

Let us now consider what one sees as one looks upward from Titan’s surface.

At first sight, it is very disappointing. All one sees is a reddish-brown haze, though a haze well above the surface. The Sun looks like a bright orange dot, but one only visible at high elevation angles, greater than about 30 – 45 degrees. But it is easily resolved with a small telescope: its angular size is 3 minutes of arc. But even when the Sun is hard to see, it would still light up the haze.

One can watch the Sun move across the sky with a period of about 16 (Earth) days, and move between 27d north and 27d south with a period of about 30 (Earth) years. As one does so, one can show that Titan is approximately spherical in another way: the Sun will be at different directions relative to different locations. One also finds that the Sun’s period is close to the Foucault-measured rotation period. So could the Sun be moving much more slowly than Titan?

There are plenty of other things to see, especially if one can get above the haze.

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Astronomy on Titan: Living There

Have you ever wondered what the Universe looks like from elsewhere in it? What the Solar System looks from elsewhere in it? I have considered that for Saturn’s largest moon Titan, and I will describe what I’ve found in my next few posts here.

I will start with what one can learn without looking upward.

Titan’s surface gravity is about 1/7 of the Earth’s, a bit less than the Moon’s at 1/6. So it should be easy to jump upward one’s own height, at least in a shirtsleeves environment. But Titan’s surface temperature is around 95 K (-188 C, -289 F), and its surface atmospheric pressure about 1.5 bar (the Earth’s is 1.013 bar). This implies a column density 11 times the Earth’s. It is almost entirely nitrogen with some methane and some other gases.

So one would need the sort of pressurized and temperature-controlled environment maintained in manned spacecraft and space stations, the sort of environment proposed for colonizing the Moon and Mars.

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