# Tag Info

Accepted

### Can a tectonically inactive planet retain a long-term atmosphere?

Yes, a tectonically inactive planet can retain a long-term atmosphere. You make the connection that a lack of plate tectonics on a planet indicates a "dead" core and thus said planet has no ...
• 14.4k

### Can a planet with no atmosphere be orbited at extremely low altitudes?

Yes, but. Firstly the 400km orbits of the ISS are already extremely low, in comparison to the 6400km radius of the Earth. See https://what-if.xkcd.com/58/ for pictures of orbits. So if you rephrase ...
• 87.6k
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### Why is there so little nitrogen in the Martian and Venusian atmospheres?

Nitrogen, with a molecular mass of 28 atomic mass units, is too light to have remained in Mars's atmosphere. Carbon dioxide, with a molecular mass of 44 amu, could (and does) exist on Mars, but it is ...
• 27.1k
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• 114k

### Why argon instead of another noble gas?

why Argon specifically? Both helium and neon are pretty lightweight, tend to vaporize easily even at low temperatures, and are chemically inert. For all these reasons combined, they tend to not get ...
• 17.5k
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### Why are Saturn bands much fainter than Jupiter's?

I'll give this one a shot. Correction is welcome. Upper atmosphere temperature. It's not just elements that give a planet color, but the temperature of elements. When we examine what a planet ...
• 22.9k
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### What is the underwater temperature of Europa?

No, nothing on Europa could possibly be photosynthesizing as we know it. Jupiter doesn't emit light, and what it reflects from the sun is not enough, plus there's no significant amount of carbon ...
Accepted

### In the end what is the ultimate matter/element in the universe, due to fusion process in stars?

If we don't wait for too long, where we don't know for sure, whether protons or atomic nuclei stay stable forever, there won't be just one single element. The most abundant element in the universe ...
• 11.2k
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### Why is twilight longer in summer than winter and shortest at the equinox

See this diagram, Now, the slant appears to be the same for June and December Solstices, doesn't it? First thing, it is a wrong conception that Sun travels more "perpendicular" to horizon in the ...
• 1,993

### Mountains are higher than the atmosphere?

This is a bit of a gray area, as an atmosphere doesn't have a clear boundary. That being said, Olympus Mons on Mars is so tall, the atmospheric pressure on top of it is only 12% the average pressure ...
• 17.5k

### Is Earth unique in its fairly clear atmosphere?

No, the clarity of the Earth's atmosphere cannot be considered unique. We don't have to speculate about exoplanets. You could argue the answer is no, because both the Moon and Mercury have (very, ...
• 114k