Skip to main content
154 votes
Accepted

Could we breathe an atmosphere that is not nitrogen based?

We can breathe pure oxygen for unlimited time if the pressure is not too high; about 0.4 bar is okay. Breathing pure oxygen at 1 bar is possible for some hours, but a longer time may damage the lungs. ...
Uwe's user avatar
  • 49k
98 votes

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

Given a pair of objects that are gravitationally bound to each other, they will orbit around their common barycenter (center of mass of the system). The object to be most logically deemed the moon ...
Anthony X's user avatar
  • 17.5k
81 votes
Accepted

Is it true that NASA is hiring a new 'planetary protection officer'?

You're observing shamefully bad journalism. The "protect Earth from aliens" bullet point in the "Highlights" section of the article was put there by an editor who either ignorantly ...
Russell Borogove's user avatar
74 votes

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

Gravity isn't just about mass, but about distance, too. Our moon has a surface gravity of about 1/6th of Earth, because it is small and less dense than the Earth is. Surface gravity of a body is ...
Starfish Prime's user avatar
57 votes
Accepted

Did the Mars rovers actually confirm the gravity of Mars?

The "gravity of Mars" is not a number but rather a complex field. The most recent is remarkably detailed, made up to spherical harmonics degree and order 120, described by 29,512 coefficients: These ...
Mark Adler's user avatar
  • 58.2k
50 votes
Accepted

Why are probes that tend to explore outer system always launched to go outwards instead of straight upwards or downwards?

Starting out from Earth, you have the free 30 km/s from Earth's movement around the Sun, which is in the plane of the ecliptic. To get far out of the plane you either have to boost a similar amount "...
Steve Linton's user avatar
  • 19.6k
48 votes

Do scientist who study martian geology typically use the term areology?

Good question. I work on the Curiosity team, and I hear "geology" all the time, but never "areology." Too bad, really, since it's a great word, and I love the R/G/B Mars series.
foobarbecue's user avatar
  • 1,405
40 votes
Accepted

What is the deepest we have penetrated a terrestrial body other than Earth?

In July 2005, the Deep Impact mission released an impactor that excavated a crater, estimated to be 100 meters wide and 30 meters deep, into comet Tempel 1.
Jim Lewis's user avatar
  • 931
39 votes

Why are probes that tend to explore outer system always launched to go outwards instead of straight upwards or downwards?

We've had 5 flyby missions to the outer solar system so far. All of them had primary missions at one or more planets. That set the main constraints for their trajectories. Anything after the last ...
Hobbes's user avatar
  • 128k
34 votes

Could an acid-proof, solar-powered aircraft stay aloft on the sunny side of Venus more-or-less indefinitely?

Thanks to one of the links in the comments above, I was able to discover that NASA wrote a fairly detailed 27 page report back in 2004 on their investigation of this idea. The synopsis says Solar ...
phil1008's user avatar
  • 5,757
33 votes

Why are the Martian poles not covered by dust?

Well, from these pictures, I think you can see that there is in fact a visible ice sheet at the poles, and you can see that global dust storms do in fact kick dust over the poles. Dust that blows into ...
Darth Pseudonym's user avatar
31 votes
Accepted

Why was Titan the first celestial body beyond Mars to be landed on?

Simple. It was the easiest to land on. Titan has an atmosphere, which makes landing there quite a bit easier than landing on Europa, which does not. In addition, Europa has only been known as an ...
PearsonArtPhoto's user avatar
  • 121k
31 votes

Do other planets and moons share Earth’s mineral diversity?

We turn to Mars, which we have studied for decades now. And we do see plenty of mineral diversity on the surface of the Red Planet, it's not just rust by any means. Curiosity's CheMin analyzer has ...
Oscar Lanzi's user avatar
  • 8,525
31 votes

By my calculation the cumulative mass of Mercury, plus Venus, plus Earth's moon, plus Mars, plus Mars' moons, total 99% of Earth's mass. Am I correct?

According to Wolfram Alpha, your calculation is correct. (The masses of Phobos and Deimos are negligible here.) It's not a particularly remarkable coincidence; glancing at a list of solar system ...
Russell Borogove's user avatar
29 votes

Why are probes that tend to explore outer system always launched to go outwards instead of straight upwards or downwards?

It is important to realize that space probes aren't really useful for finding objects in deep space. Space is so empty that a probe sent in a random "exploratory" direction would have a negligible ...
Mark Foskey's user avatar
  • 11.3k
29 votes
Accepted

How does Titan have hydrogen in its atmosphere?

How does Titan have Hydrogen in it's atmopshere? Hydrogen is a trace gas in Titan's atmosphere (0.099% per the wikipedia article on Titan's atmosphere). Titan's scant amount of hydrogen in its ...
David Hammen's user avatar
28 votes

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

Yes, it is possible. As James K observed in a comment, the surface gravity of Uranus is slightly less than that of Earth, but its mass is 14 times larger. If Earth were orbiting Uranus, it would be a ...
Mark Foskey's user avatar
  • 11.3k
28 votes

How does a planet's gravity push away smaller bodies that would otherwise intersect its orbit?

I feel the need to correct some issues that were brought up in the other answers. Yes, gravity is an attraction-only force. But due to its relative weakness, objects in space can attain large ...
AtmosphericPrisonEscape's user avatar
25 votes

What defines the radius of a ball of gas like Jupiter?

The radius of Jupiter and the other gas giants is defined, somewhat arbitrarily, to be the radius at which the atmosphere has a pressure of 1 bar. As your question points out, they had to pick ...
Mark Adler's user avatar
  • 58.2k
25 votes

Does the atmospheric pressure of Mars fluctuate because of the seasonal evaporation of the polar ice caps?

According to https://marsed.asu.edu/mep/atmosphere The deep cold southern polar winter removes CO2 gas from the atmosphere by freezing it directly onto the south polar cap. As temperatures drop below ...
Alan Birtles's user avatar
  • 2,066
23 votes
Accepted

Do scientist who study martian geology typically use the term areology?

A search on arXiv for "areology" produces no results. A search on ADS produces two results (one of which has the subtitle "The Geological Environment of Mars"). So the term is ...
usernumber's user avatar
  • 5,068
23 votes

Term for deformation due to gravity

The generic term is tidal deformation. At a distance of ~385000 km, the Moon subtly distorts the shape of the Earth. Those distortions are readily visible in the Earth's oceanic tides, and not quite ...
David Hammen's user avatar
22 votes

Which of the four inner planets has the strongest magnetic field, Mars, Mercury, Venus, or Earth?

Which of the four terrestrial planets has the strongest magnetic field, Mars, Mercury, Venus, or Earth? The Earth, by far. The four giant planets have rather strong magnetic fields. Amongst the ...
David Hammen's user avatar
21 votes
Accepted

How tall are Pluto's mountains? Are they the tallest ice features in the Solar System?

How tall are these things? Are they made of ice? Are they the tallest things on Pluto? Are these the tallest ice features in the Solar System? "New close-up images of a region near Pluto’s ...
ceejayoz's user avatar
  • 1,288
21 votes

Do other planets and moons share Earth’s mineral diversity?

They do not! The reasons for this are simple: minerals are semi-stable configurations of elements formed in certain pressure-temperature-redox conditions. A planet in the possession of active plate ...
Anton Hengst's user avatar
  • 10.7k
21 votes

BBC: "In 2009 Prof McDowell & other astronomers performed an experiment in which a similar-sized rocket was crashed into the Moon." Really? Which one?

"2009 impact" would probably be when the LCROSS/LRO upper stage was crashed into a crater at the Moon's south pole. The LCROSS Centaur upper stage had a mass at impact of around 2300 kg; an ...
Mark's user avatar
  • 15.3k
20 votes

Could we breathe an atmosphere that is not nitrogen based?

Yes, we don't require nitrogen to breathe. For example, NASA astronauts used to use a pure oxygen environment. The complication with this environment was the risk of fire. For more information: Why ...
called2voyage's user avatar
  • 23.7k
19 votes
Accepted

Is Mohs scale of mineral hardness applicable for rocks and minerals of terrestrial planets other than Earth?

Yes, because for the vast majority of minerals you can find in space, they are the same as those you can find (or synthesize) on Earth. A pyrite in space is a pyrite just like on Earth. A wollastonite ...
Anton Hengst's user avatar
  • 10.7k
19 votes

How does Titan have hydrogen in its atmosphere?

The chemistry of Titan's atmosphere is actually quite complex. Different reactions occur at different altitudes and there are a wide range of minor constituents in the atmosphere. One of those ...
Slarty's user avatar
  • 9,560

Only top scored, non community-wiki answers of a minimum length are eligible