Questions tagged [planetary-science]

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125 views

Caves traced in nine planets of solar system

Are there chances of caves being found or traced on other planets of the solar system? What's the solution? Manufacturing special telescopes for viewing or observing caves on other planets? or ...
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Qualities of gas giant atmospheres at a density of 1 gram per cubic centimeter

At what depth in the atmospheres of the gas giants does the density of their atmospheres equal 1 gram per cubic centimeter? What is the pressure and temperature at these depths? Are the radiations ...
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Could rocks from Earth have reached the Kuiper belt, or Neptune at least? If so, how?

This answer (currently edit 3) to How certain are we that we have not sent life to other planets/moons? begins: First of all, rocks from Earth are probably just about everywhere in the Solar System. ...
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Is dust the only reason why the Martian sky is so bright?

The atmospheric pressure on the surface of Mars is 0.00609 atm on average and 0.012 atm at most in the Hellas Basin. On Earth, at these pressures, which are found at altitudes about 30-35 km (19-22 mi)...
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What is 'surface acceleration' of a planet or other body? As opposed to its 'g' (gravity)?

The Mars Fact Sheet at NASA (their NSSDC or NSSDCA section, whatever that means) lists a value for 'surface acceleration' just below one for 'surface gravity'. They also have the values for Earth, ...
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How fast is Neptune getting brighter? When was was this first noticed and reported?

This answer to Compute Planet's Apparent Visual Magnitude reports the new work on planetary magnitudes, and contains an intriguing blurb about Neptune: Neptune keeps getting brighter. No one knows ...
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Why is there so little nitrogen in the Martian and Venusian atmospheres?

Why don't our neighbors have much nitrogen? You would think that, without 'nitrogen-fixing' organisms and such, there might be more.....
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1answer
122 views

Can tidally locked planets have liquid oceans on their night side, and would such a planet be habitable?

Let's say we have a tidally locked planet orbiting a star. And let's say that the conditions on its surface are just right for water to exist on its surface. Conventional wisdom says that the water on ...
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Magneto tail effect on the other planet in a binary planet system

Let's say there are 2 earth sized planets orbiting each other around 750,000km apart and at a distance of roughly 1.2 AU from a sunlike star with a mass of 1.105 solar masses. Since they are binary, ...
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Binary planet orbital distance

From reading various sources online, I see that some people talk about binary planets in very tight orbits (around 1 or 2 planet radii). I am wondering if it is possible for a binary planet (Double ...
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1answer
116 views

Do gas giants have a core?

I have always wondered how Jupiter and the other gas giants worked when it came to having a core(If they have one). Would it be rocky or liquid, or can it be a gas. Every time I have asked this ...
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When could the Roche limit be larger than the Hill sphere?

This answer to Are Saturn's rings stable? begins with: Most of Saturn's rings are inside it's Roche limit, which means they will never clump together. Tidal forces prevent this from happening. I ...
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Why are we so quick to proclaim the geological inhospitability of other planets based on extremely minimal information?

Now, I'm not questioning claims that any planet in the Solar System is atmospherically or externally inhospitable, but claims made that other planets have geology that is extremely hostile to ...
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50 views

Does Earth's magnetic field become stronger when a solar flare hits?

This curiosity arises as follows: when ejecta from a strong solar flare hits Earth, will the Earth somehow counter its impact with a stronger magnetic field. Or, earth's magnetic field as limited ...
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3answers
548 views

Is there a way to tell the difference between earth andesite from Mars

I'm curios if there is a way to test if this sample might be Martian andesite. What type of oxygen isotope (or other) test can be done to address this in some way? As background, any information ...
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256 views

How much damage would collision with a similar mass primordial black hole do to earth?

All this talk of Planet 9 perhaps being a primordial black hole (PBH) made me wonder how dangerous a PBH collision with earth would really be. Specifically, if earth collided with a PBH of 1 earth ...
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1answer
100 views

Why would a tidally-locked rocky planet have a first-order spherical harmonic surface temperature distribution?

The new Letter to Nature Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b (also ArXiv) analyzes the thermal infrared light curve from the system (about 4.5 to 5.5 um). The planet ...
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240 views

Why is Saturn invisible in this radar image of its rings?

The image below is from Radar imaging of Saturn’s rings Nicholson, P. D. et al., Icarus 177 (2005) 32–62, doi:10.1016/j.icarus.2005.03.023 and discussed further in this answer to How did Arecibo ...
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595 views

Neptune's Internal Heat Source

Unlike its sister planet Uranus,Neptune has a substantial internal heat source which gives rise to a dynamic atmosphere & weather. Wikipedia says: As with Uranus, the source of this heating ...
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319 views

Is the boulder on the peak of Tycho Crater the core of the impactor, or is it a random rock?

There's a strikingly visible boulder sitting right at the top of the peak complex in the center of Tycho Crater on the Moon. Is it just a coincidence that this gigantic, bright rock is sitting dead ...
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4answers
127 views

Is it plausible for a planet that is positioned in the habitable area of a solar system to have little extractable metals?

I am big fan of Asimov's Foundation and I am wondering about the plausibility of some of Foundation's imagined words. According to this article Terminus was a special world with little metals: It ...
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1answer
63 views

Does Mars' “Northern ocean” have another name? What about the “Inland Sea”?

The March 15, 2019 Phys.org article A NASA spacecraft may have explored the edges of an early Mars sea in 1997 shows a stylized map of an area on Mars where the Mars Pathfinder landed and uses colors ...
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215 views

How can it be known that Venus does not have plate tectonics?

This answer provides some insight into Venus' surface geology: Water may be necessary as a lubricant for plate tectonics. Whether or not this is the case, Venus does not have plate tectonics. It ...
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1answer
71 views

How do they measure sub-centimeter wave height on a moon of Saturn?

Michael Stevens from V-Sauce has a video called The Mandelbrot Set on a different channel. At 12:56 he says: There’s a moon of Saturn that has liquid hydrocarbon ...
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How did early estimates of a “potato radius” set 1 eV ~ GMμ/R and get 200 to 300 km?

@DavidHammen's answer explains that Goblin has roughly a potato radius and I can't believe I just wrote Goblin and potato in a serious question. That happened. The linked paper; The Potato Radius: a ...
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1answer
108 views

Total rotational angular momentum estimates for Jupiter?

I wrote a quickie answer where I estimate the total rotational angular momentum of Jupiter as about 7E+38 kg m^2/s. However it bothers me because one of the sources gets this number assuming uniform ...
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1answer
80 views

How would you relate the respective solar gravitational pulls of two planets?

I was asked this question: How much weaker is the gravitational pull of the Sun on Neptune at 30 AU, than it is on Earth at 1 AU? How would I even begin to determine this?
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Predicting Temperature Variation on Planets with High Eccentricity or Long Diurnal Periods

Whew! That title was a mouth-full, but accurate I hope. What I'm trying to figure out is a model for calculating the approximate temperature variation for a generally earth-like planet (similar ...
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0answers
174 views

Why does the axial tilt & the rotation speed of Saturn & Jupiter vary so much?

I have seen Jupiter and its 4 largest moons in a telescope, several times. The moons are always aligned in a line. This is fine. Very interesting. But.. in case of Saturn, not only that we can see its ...
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1answer
213 views

Wondering about a horseshoe orbit

Since I'm not a physicist, I want to know how that system works. For instance, if there was a planet, very similar to the Earth, but with two moons, and the moons where in a horseshoe orbit, how does ...
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3answers
680 views

How many things are wrong in this “artist view” of the TRAPPIST-1 system?

There is a this poster on the NASA site ( that irks me. Of course its an artist's fantasy, but since it is on a NASA site, I see people considering it as scientifically accurate. So, beyond the two ...
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173 views

Is there an established distinction between a geyser and a cryovolcano in solar system bodies?

Is there an established distinction between a geyser and a cryovolcano in the context of cold solar-system bodies such as the moons of Jupiter and Saturn, or Kuiper belt objects (e.g. Pluto)? Both ...
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How do astronomers choose their research topic? [closed]

Astronomers don't face much of an ordinary jobs market in their "trade". What does the process look like from choosing a topic for the PhD to doing research in a specific topic? Let's say that you're ...