Questions tagged [moons]

Questions about celestial bodies that orbit another celestial body.

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48
votes
6answers
14k views

Is it possible for a moon to have a higher surface gravity than the planet it is attached to?

Is it possible that a moon has a higher surface gravity than its planet? I guess it would mean that the moon has a higher mass, but then it would be the planet gravitating around the moon and the ...
45
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7answers
18k views

Why do artificial satellites need orbit correction, but natural ones don't?

No matter how much you fine-tune a satellite's orbit up front, it needs periodic adjustments. It's usually done through tiny rocket bursts. The system and fuel to do that costs money and weight, and, ...
33
votes
1answer
2k views

Have any of the rovers ever recorded a solar eclipse on Mars?

I've heard a rumor that Curiosity rover sent a recording about Phobos covering the Sun on the Martian sky. Did it happen? If yes, how frequently could such things be recorded?
20
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2answers
2k views

Escaping moons conflict with what I understand of gravity

I have known that the Earth's Moon, let's call it Luna (tip of the hat to The Expanse), has been slowly but surely increasing it's distance from the Earth by a small measure each year. This week I ...
20
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1answer
3k views

If colonists burrowed far enough under the ice on Ganymede or Europa, would the ice provide adequate protection for them from Jupiter's radiation?

This is a hypothetical question I'm asking as a SF writer, and the time setting would be approximately 2,250 AD.
16
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2answers
510 views

How large could Hyperion be and stay porous?

Here is a question originating on the Worldbuilding stack. Hyperion is porous, with a density of 0.55 g/cc; a little more than half that of water. from https://www.space.com/20770-hyperion-moon.html ...
12
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2answers
9k views

Would it be possible to “fall off” Phobos? [closed]

Phobos (one of Mars' moons) has the following dimensions: 27 × 22 × 18 km. It has low mass, and little or no gravity/atmosphere. Let's just assume that it's possible to walk around on Phobos without ...
11
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2answers
871 views

Why are sections of Cassini photographs blurred?

In this photograph of Rhea, taken by the Cassini orbiter, there are sections near the terminator that are very blurred, a stark contrast from the crisp sharpness of the rest of the image. The blurred ...
11
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1answer
487 views

Is it possible for moons to have their own moons?

I'm wondering, if it's possible for moons to have their own natural satellites, something big enough to be spherical? Stars have planets, planets have moons. Is it possible that moons have moons too?
10
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5answers
3k views

Pluto's satellites other than Charon orbits around Pluto or center of gravity between Pluto and Charon?

As the center of gravity between Pluto and Charon is outside Pluto does Pluto's satellites other than Charon such as Nix, Hydra, Kerberos or Styx orbits around Pluto or the COG?
10
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2answers
2k views

Is there a term to refer to a planet and its accompanying moons as a whole collection?

I am trying to find out of there is a term that can be used when referring to both a planet and any accompanying moons (if present) as a whole collection. For example if you were to refer to Mars and ...
10
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1answer
333 views

How seriously did astronomers take the idea of a hollow Phobos?

Phobos, the larger moon of Mars, was once theorized to be hollow by Iosif Shklovsky. Plenty of publications reference the idea (such as this snippet from Popular Science), but did anyone take it ...
9
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1answer
331 views

Many moons in same orbit

Is it possible to have a stable orbit comprised of many moons(>2) that keep themselves roughly equal distance apart? Sort of like Epimetheus and Janus around Saturn but comprised of many moons. The ...
9
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1answer
654 views

Titan - Is the source of so much Methane being overlooked?

Is the source of so much Methane on Titan being overlooked? Tons of very intelligent and knowledgeable people already looked at it, so the answer in undoubtedly "no", so I guess my question is more ...
8
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1answer
437 views

Why were Nix, Cerberos and Styx discovered later than Charon?

Charon, a moon of Pluto, was discovered in 1978. Today we know that Pluto has three additional moons, but they were discovered 3 decades later? Also, Hubble Space Telescope was in operation since 1990 ...
7
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2answers
1k views

Would a Foucault pendulum work on the Moon and on the Galilean moons?

I wonder whether the Moon and the Jovian moons spin fast enough for a Foucault pendulum to swing on their poles. For instance, I think that it wouldn't swing on Mercury and Venus because these planets ...
7
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3answers
231 views

Why is Enceladus the “most interesting place for astrobiology” in the Solar System other than Earth?

In season 1 episode 1 of Space's Deepest Secrets (IMDB), Dr. Chris McKay, a planetary scientist for NASA, says around 1h:40m into the show, "This is the single most important and interesting place for ...
7
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2answers
1k views

Hohmann Transfer Equation of Motion

I'm working on a school project on calculating the Keplerian orbital motion of objects and then plotting/animating the trajectories. One feature I want to include is plotting a Hohmann transfer from ...
6
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3answers
412 views

Does NASA plan to land on Europa?

I recently studied that life may exist on Europa, an icy moon of Jupiter. Does NASA plan to land a spacecraft on Europa to study its environment in the near future?
6
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3answers
4k views

Which planets and moons can you walk on?

Which planets and moons have a surface where you could survive with a conventional or near-future spacesuit? Assume oxygen, water, and food supplies are accounted for, but roughly current limitations ...
6
votes
1answer
480 views

What is responsible for the different colors of Iapetus?

Iapetus, one of the moons of Saturn, is known for having two distinct color regions, one bright and the other dark. This was noted as early as the 17th century. This region can be seen below, and even ...
6
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1answer
471 views

Where does Io's sulfur come from?

This answer on Movies.SE collects some fascinating facts about the sulfur-dominated surface and atmosphere of Jupiter's moon Io. But it made me wonder where all the sulfur comes from in the first ...
5
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1answer
1k views

Are there any natural circular orbits?

I just saw How does orbital eccentricity affect positions of Lagrange points $L_4$ and $L_5$? and it questions the difference between circular and elliptical orbits. We know the Moon does not have a ...
5
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3answers
264 views

Has any other term been used for a solar day on a solar system body besides “sol” on Mars?

My interest was piqued by this question and answer. For several reasons NASA needed to refer frequently and extensively to a Martian solar day, and "sol" became the nom du jour. There have been ...
5
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3answers
748 views

Keplerian approximations for moons as well as planets

I'm writing code to simulate planetary and lunar orbits in a heliocentric reference plane. I'm using E.M. Standish's Keplerian Elements for Approximate Positions of the Major Planets as my reference ...
5
votes
1answer
236 views

Tallest mountains on the Galilean satellites?

Suppose I want to climb the tallest mountain on each of the four Galilean satellites. Is it known what they are? Io has one of the most spectacularly tall mountains in the solar system, Boösaule ...
5
votes
1answer
118 views

How is salt transported from the subsurface ocean and ejected with the plumes of water from Enceladus?

My limited understanding is that the plumes of water vapor and ice seen rising nearly vertically from the ice surfaces of Enceladus and other ice/water covered moons of Jupiter and Saturn are not ...
5
votes
1answer
189 views

Will JUNO do any science of Jupiter's Moons?

It seems like the primary focus of JUNO is to get a better idea of how Jupiter works. The Science Objectives listed on Wikipedia don't seem to include anything about Jupiter's moons, other than a ...
5
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0answers
95 views

Why couldn't New Horizons try again to search for small moons of Pluto?

I was reading Alan Stern and David Grinspoon's Chasing New Horizons, the story of the quarter-century effort to prepare, enable, and run New Horizons' mission to Pluto. As many readers know, it ...
5
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0answers
90 views

How did scientists experimentally confirm that Saturn's ravioli-shaped moons had highly porous surfaces?

The NASA News article NASA's Cassini Finds Saturn's Rings Coat Tiny Moons says: The new research, from data gathered by six of Cassini's instruments before its mission ended in 2017, is a clear ...
4
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1answer
426 views

Can we detect if Mars has small, stone-size moonlets?

If there is a stone-size moonlet orbiting around Mars, can we detect it?
4
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3answers
910 views

Data for Moons in the Solar System with Masses

I'm looking for a simple machine-readable table with basic parameters for all the known moons of the planets in the solar system. Stumbling around the internet, I can find plenty of sources like this ...
4
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2answers
366 views

Is It Easier To Hohmann Transfer to a Retrograde Satellite or to a Prograde Satellite?

Suppose I start on Earth and make a Hohmann transfer to Neptune. After traveling along my initial trajectory, I arrive at the Neptunian system. However, the objects in the Neptune system are going ...
4
votes
2answers
138 views

Is Hydra of Pluto cut unusually, or just darkened on its surface?

The image of Hydra recently released shows a sharply edged black half oval cutting deep into its bottom as in the image below. Is it dark sky behind an open gap we see, or just unreflective matter on ...
4
votes
2answers
196 views

How feasible is a natural satellite (moon) that moves between planets?

I'm designing a world, and I really like the idea of a recurring moon. If a planet were in the proper orbital resonance with another planet, is it possible that moons might occasionally traverse ...
4
votes
1answer
593 views

Do Lagrange-like regions temporarily appear around planets with multiple moons?

Lasting Lagrange points only exist where two bodies of mass dominate. But in the midst of for example the synchronous Jovian moons, is there a calendar and map for when a spacecraft can be near enough ...
4
votes
2answers
479 views

Could a rogue planet's moons harbor life?

Because stars kill stuff with radiation, flares, etc, then die taking planets with them, might it not be easier for living things to live on a rogue planet's moon? Say you had a rogue Jupiter-like ...
4
votes
1answer
133 views

Is the equatorial mountain range of Iapetus due to cold erosion?

Iapetus, satellite of Saturn, has a huge mountain range along about half its equator. On this list of our solar system's biggest mountains, it is the only entry with uncertain origin. ..The ...
3
votes
1answer
77 views

Would a large impactor on an ice moon cause a thinning of the ice surface?

While it has not been confirmed, Callisto (Jupiter IV) could potentially have a small subsurface ocean below a thick ~100 km ice layer, according to Wikipedia. A mission to explore that ocean might ...
3
votes
1answer
87 views

Should a Europa clipper use a retrograde orbit?

A "clipper", as I understand it, is orbiting a planet to repeatedly flyby one of its moons. Mariner 10 orbited the Sun to fly by Mercury 3 times. Should clippers in general use retrograde orbits in ...
3
votes
0answers
84 views

Iapetus - Destabilized rings to mountains?

I was reading an article about a ring that was destabilized out of orbit on one of Saturns moons. I got there by looking for mountains because of this question (unrelated mostly). Here's a picture of ...
3
votes
0answers
50 views

Is there any moon in our solar system which we could terraform relatively fast? [duplicate]

I am just curious as to whether there is any moon in our solar system which could be terraformed or at least made into a livable moon for us. By fast i mean as fast as possible, given our current ...
2
votes
1answer
259 views

Moon Polar Days And Night

Moon's rotation axis from the orbit plane of earth is about 1.54° tilted. Just like earth because of tilt, do polar regions experience 6 months day and 6 months night? If so, aren't these places ...
2
votes
1answer
94 views

Tides on other bodies

Since the tides on the moon have an antieffect on the other side of earth, (still don't quite understand how that works), shouldn't the gas giants deform when their moons move around in their orbits? ...
2
votes
2answers
241 views

Is “interlunar” applicable to the moons of other planets?

We have intergalactic to describe the area between galaxies. And interstellar space is between star systems. And interplanetary is between planets. Is the term "interlunar" applicable to the space ...
2
votes
1answer
125 views

Next lander/rover mission

Beyond Mars and 67P, what is the next most viable mission for probe landing? How far are we from sending one to the Jupiter or Saturn system?
2
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0answers
176 views

Why haven't Saturn's rings coalesced into moons/satellites? [closed]

The rings of Saturn are made up of tiny particles/rocks/ice that all orbit Saturn. Each individual particle is bound to its orbit because of Saturn's gravity, but each particle also pulls on all of ...
1
vote
1answer
126 views

Bombing the Moon: how much debris would there be in stable orbit?

If someone had actually nuked the Moon (e.g. here or Bombing Moon and Mars: What would it look like? ), what's the probability of some debris reaching a stable orbit around the Moon? This would not ...
1
vote
1answer
505 views

Why are most of Jupiter's moons retrograde?

Jupiter's small moons are likely captured objects. I would've expected half of them to be captured in retrograde orbit, between 90 and 180 degrees inclination. But out of 65 lesser satellites, only 11 ...
1
vote
1answer
4k views

Satellites in retrograde vs prograde orbit [closed]

I read somewhere that Israel launched satellites in retrograde orbit. America also has some satellites in retrograde orbit. I am new to this concept, so I am curious: 1. What are the benefits/...