Questions tagged [planetary-science]

The multi-disciplinary study of the geomorphology, geology, chemistry, meteorology, oceanography, hydrology, astronomy and astrophysics of the planets and other objects within the solar system.

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What factors determine the number of Hadley cells for a planet?

We know (think?) that Earth has three Hadley cells per hemisphere, but from observing gas giants such as Jupiter, we see that they have many more cells. According to a link from a comment in this ...
congusbongus's user avatar
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In an Earth-like planet with no history of carbon-based life forms, would there be limestone?

The extent of my understanding of limestone is about what Wikipedia says at the very top of the page: Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such ...
TylerH's user avatar
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How do we know the asteroids formed at the same time as earth?

In continuation of the question Why is Earth's age given by dating meteorites rather than its own rocks?, what evidence do we have that the asteroids indeed formed at the same time as earth? Is there ...
Nathaniel Bubis's user avatar
28 votes
2 answers
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What sort of climate zones would be present if Earth was tilted like Uranus?

The three main climate zones on Earth are tropics, temperate and polar. Due to Earth's axial tilt, the three zones experience different seasonal patterns: The tropics experience 2 or 4 wet/dry ...
congusbongus's user avatar
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23 votes
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What properties must a rocky body possess in order to exhibit plate tectonics?

The Earth exhibits plate tectonics, but the other terrestrial planets do not (though Mars and Venus may have exhibited plate tectonics in the past). What is "special" about Earth that allows it to ...
senshin's user avatar
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9 votes
1 answer
221 views

What is the current status of geophysical global cooling theory?

Plate tectonics effectively rubbished the theory of geophysical global cooling as a means of explaining many surface features on the Earth. However, this wiki says that the same process is responsible ...
christopherlovell's user avatar
5 votes
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How could the solar wind cause strange magnetic pulses on Mars at midnight?

24-Feb-2020 NASA News item A Year of Surprising Science From NASA's InSight Mars Mission says: A new understanding of Mars is beginning to emerge, thanks to the first year of NASA's InSight lander ...
uhoh's user avatar
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What time and date is the sun directly overhead a given place on Earth?

In different regions, the sun is directly overhead at different times of the year. When do these event happen?
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How and why did the oceans form on Earth but not on other planets?

Earth is the only planet in our solar system that has copious amounts of water on it. Where did this water come from and why is there so much water on Earth compared to every other planet in the ...
Kenshin's user avatar
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26 votes
2 answers
988 views

Why do some planets have lots of $\mathrm{N_2}$ and others none?

Earth, Titan and Venus all have large amounts of $\mathrm{N_2}$ in their atmospheres. (In the case of Venus it's a small proportion, but Venus' atmosphere is very thick, and the total mass of $\mathrm{...
N. Virgo's user avatar
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Why do Earth and Venus have different atmospheres?

Venus appears to be the closest to Earth in mass, density, size, etc. - though they clearly have different atmospheres. Why do Earth and Venus have different atmospheres?
blunders's user avatar
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Will the Earth ever stop rotating?

It is well known that the Earth's rotation is slowing down and that millions of years ago there was a point in time where there was only a mere 20 hours in a day on Earth. My question is in two parts....
Kenshin's user avatar
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19 votes
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To what accuracy and precision do we know the volume of the Earth?

Satellites such as GOCE and GRACE measure the geoid with unprecedented accuracy. Altimeters can determine local surface elevation with millimetre-precision. This makes me wonder: to what precision ...
gerrit's user avatar
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Can Venus be considered to be tectonically active?

Venus is noted for its absence of spreading ridges, transform faults, and subduction zones, which are characteristic of plate tectonics on Earth. But given that it exhibits rift zones, mountain belts ...
decvalts's user avatar
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18 votes
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Why does the earth spin clockwise?

Why does earth rotate in a clockwise direction? Did a large meteor collide with earth causing earth to rotate? If that is what happened, could another, larger meteor cause earth to reverse its ...
tux's user avatar
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14 votes
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What kinds of remote sensing required to observe methanogenic life on Titan?

Inspired by Chris McKay's Possibilities for methanogenic life in liquid methane on the surface of Titan. In the paper, the PI's found that the consumed acetylene, ethane, and other organic solids ...
Neo's user avatar
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12 votes
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What is the fastest the Earth has ever spun?

How fast can the Earth rotate and support life? In prehistoric times, dinosaurs were so massive that archeologists wonder how they were not crushed under their own weight. Could a faster spinning ...
Muze's user avatar
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10 votes
1 answer
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How would weather change on a tidally-locked terrestrial planet?

On Earth, weather is very much affected by the Earth's rotation around its axis and around the Sun. Even locations that are almost on the equator do have strong annual variations in precipitation and ...
Irigi's user avatar
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8 votes
1 answer
969 views

What "g" would be needed to keep helium on Earth?

I know that helium is a very light and rare gas on Earth because Earths gravity is not strong enough to keep it. Instead, helium and hydrogen are rising through the atmosphere and escape into outer ...
Petr Hykš's user avatar
8 votes
2 answers
2k views

Why is earth's axis tilted?

Why is the axis of earth tilted? It can't possibly be that the Northern hemisphere is larger causing it to be pulled toward the sun, because then it would always be summer in the N hemisphere and ...
tux's user avatar
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5 votes
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Mars' strange magnetic pulses at midnight; besides the solar wind what are other possible causes?

24-Feb-2020 NASA News item A Year of Surprising Science From NASA's InSight Mars Mission says: A new understanding of Mars is beginning to emerge, thanks to the first year of NASA's InSight lander ...
uhoh's user avatar
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3 votes
2 answers
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Now Mars is pulsing 3 times per night in the UV, can anyone explain these waves in simple terms? Do these waves have analogies on Earth?

I link below to questions on another kind of Mars pulse) Phys.org's NASA's Maven observes Martian night sky pulsing in ultraviolet light links to the new paper Imaging of Martian Circulation Patterns ...
uhoh's user avatar
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3 votes
4 answers
382 views

Do we know anything about the nature of Earth's core that hasn't come from magnetic or seismic measurements?

There is much known about Earth's core from painstaking analysis of seismic data, and from detailed magnetic field maps and trends over time. Are there any other measurements that have contributed to ...
uhoh's user avatar
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0 votes
3 answers
617 views

Which physical parameters can we actually measure to confirm the existence of the Greenhouse Effect (GHE)? [closed]

The theory of a GHE in a planetary atmosphere is rather well known. Many claim it is no longer a theory but actually proven as a fact. However I have been reading a lot of things Richard Feynman said ...
user7733's user avatar
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