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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Exploring the Earth’s Interior

How did we learn about the Earth’s interior? I will channel my inner Isaac Asimov here, and explain how we did it.

One can do so by digging downward, and some mines have been dug to some impressive depths by ordinary standards. The champions are currently the TauTona and Mponeng gold mines near Johannesburg, South Africa, going down some 4 km (2.5 mi). But that’s barely a scratch compared to the Earth’s average radius of about 6371 km (3959 mi).

There are also tunnels excavated by various natural effects — caves — but those don’t extend very far down either. The deepest known cave is the Krubera Cave in the Abkhazia district of Asian Georgia, at about 2.2 km (1.4 mi).

So we have to use more indirect methods: magnetism, earthquake waves, gravity, eruptions and overthrusts, and meteorite composition.

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