# Tag Info

19

"It's believed that the Earth was rotating about once every 5 hours before the theorized collision with a Mars sized coorbiting object referred to as Theia." Almost. Theia did not have to be co-orbiting, just an intersecting orbit. We have no idea what the Earth's spin was before the collision, but it is theorized that the Earth rotation had a 5 ...

12

Our own magnetic field is generated by convection currents in Earth's liquid outer core. A useful summary from Physics.org: Differences in temperature, pressure and composition within the outer core cause convection currents in the molten metal as cool, dense matter sinks whilst warm, less dense matter rises. This flow of liquid iron generates ...

10

This is a very interesting question. Of course, as you noted, you have simplified things quite a bit; there are other factors besides temperature that affect habitability. Regarding Venus, you probably know that Venus is extremely hot at its surface not just because it is closer to the Sun, but because it has a thick CO2 atmosphere and is warmed by the ...

10

The effect is called apparent retrograde motion. What happens is that Mars has a 'direction opposite to that of other bodies within its system as observed from a particular vantage point' when this loop occurs. That's a bunch of words that don't mean a lot to me. A picture is worth a thousand clearer words: (Imagine this turned sideways and you get the ...

10

Many models shown in books or television show a very populated asteroid belt but in fact the belt is mostly empty. To answer your question, the inclination of the asteroids vary a lot going from 0° to 40° although most off them are in between 0° and 30°; See The orbital element distributions of real and modelled asteroids. So yes it would be 3 dimensional. ...

10

The loss of the Martian atmosphere can be mostly attributed to its mass. The reason why Earth still has an atmosphere made of lighter elements is because with larger mass comes larger escape velocity, which is the speed at which an atom's kinetic energy overcomes the gravitational potential energy of its planet. The distribution of speeds of most gasses can ...

9

The impact of Phobos, even in one piece (less likely), would be different from Chicxulub. Phobos is probably a little larger than the Chicxulub impactor, but much slower, and comes in almost perfectly tangential. The impact energy would be less than a 10th of the Chicxulub impact, and the energy would be distributed over a large region around the Martian ...

9

Either or neither. It's impossible to tell from the present. If runaway climate change occurs, then yes, the conditions on Venus could be a potential analogue for the kind of environment on Earth due to the greenhouse effect. Mars's atmosphere is assumed to have been much thicker in the past, otherwise it could not have sustained liquid water on the ...

8

The most likely candidate would be the Tardigrade. These little guys handle vacuum and radiation just fine. So long as water is provided, according to tests done in LEO the Tardigrade would survive on Mars. Even if they do dehydrate, they spring back to life once water is provided again.

8

Self-sufficiency is an incredibly broad term. We could argue that yes, there is water on the Moon, and that yes, there are viable ways to produce required electricity in self-sustainable ways, but the real question is, are there areas on the Moon that would be viable for both at the same time. You see, the most likely place where surface or near subsurface ...

8

We can look up for water in the atmosphere of the planet, not at the planet itself. We can do that when a planet passes in front of a star. That tehnique is called transmission spectroscopy.

8

The inverse-fourth-power law you're referring to is valid for light emitted from a source, reflected non-specularly — i.e. in all directions — from a reflector, and detected by the original emitter. If the reflector is a mirror, the observed flux just follows the normal inverse-square law with the nominator equal to $(2d)^2$ instead of $d^2$, since the ...

7

The research in other answers helped me come across the actual International Astronomical Union (IAU) standard: The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system. The north of the invariable plane is the side that Earth's North pole points to. In fact, one of our other users has observed: ...

7

I'll add to Wayfaring Stranger's comments. In fact most of the time you would be able to see fewer stars in the night sky of Mars, than in a good dark night sky on Earth, because of dust obscuration. Even in favourable conditions, the optical depth of the Martian atmosphere is usally somewhere between 0.5 and 1 per airmass. (Petrova et al. 2012; Lemmon et ...

6

On 16 June 2014 at 11:45pm, it was up not far from 220az 30alt. It was actually 232az, 27alt, almost level and to the right of Spica. It would have been easily seen without binoculars being -0.2 visual magnitude. You can answer this sort of question yourself by getting a planetarium app like Stellarium, The Sky X, Sky Safari, or one of many others.

6

On the surface of Mars probably none, since it's too dry or too cold, or both, to stay active. Spores or other dormant forms probably could survive for centuries, until radiation will gradually destroy the organic molecules necessary to get back into an active state. But there are "Mars Special Regions", where either Earth microbes or potential Martian ...

6

This is a question that cannot be accurately answered. However, the closest to a honest and accurate answer would be that neither, since the Earth is going to "evolve" (curious choice of words) towards the Earth's fate. The presence of humans means any purely physical projections need to be taken with a grain of salt. Our ability to influence the planet ...

6

If you are asking about short-term effects related to human's effect on the climate, the answer is (obviously) unclear. But in the very long term, Earth is likely to evolve to a more Venus-like state. Over the next billion years or so, the Sun's luminosity will slowly increase, which will heat Earth's surface. As a result, more water vapor will evaporate ...

5

Mars is the only planet providing rocks with a similar chemical composition and age. So the origin of the meteorite is evident. This doesn't mean, that it's absolutely waterproof. There might have existed protoplanets similar to Mars 4 billion years ago, which since then have been swallowed by Jupiter, the Sun, or have been ejected out of the solar system. ...

5

The circumstellar habitalbe zone can be defined as the distance range around a star, where the mean temperature of a rotating planet would be between 0 and 100 centigrades, if radiation (heat) received from the star and thermal radiation emitted by the planet form an equilibrium. But that's only a rule of thumb. It has been redefined, and is still disputed. ...

5

That's one of the big questions. ESA scientists, at least, think it's worth looking for underground life. See ExoMars mission. More likely than earth worms are microbes, since some microbes on Earth live under similar conditions as presumed for underground Mars.

5

None of these things were named after chocolate. Milky Way The name comes from a Greek myth, at the end of which Hera - Zeus' wife - spills her breast milk. In places where the sky has not been affected by light pollution, the Milky Way looks like a milky-white streak. Hence the name. The chocolate of the same name was introduced in 1923. Apparently, it ...

5

As you know, but other readers maybe don't, on Earth the sunlight is scattered by Rayleigh scattering on the molecules of the atmosphere. This has quite a strong wavelength dependence, with blue light being scattered much more efficiently than red light. On Mars, there is almost no atmosphere. Instead, the Sun's light is scattered by the fine, red dust ...

5

Space, as Randall notes, is really dry. Mars, (recent discoveries notwithstanding) is not much moister. In these conditions, bodies mummify. The microbes that live in you, wouldn't survive the freezing, dessication and radiation. There is no real upper limit on how long a mummified body could exist in space. There would be nothing to cause the body to ...

5

I'm going to say no, for a few reasons, but if anyone wants to give a more detailed answer, feel free. 1) Planets and moons that form inside the frost-line have much less water and other ices than those that form outside. Mars likely once had water and oceans but if it had formed outside the frost-line it should have a lot more water and a lower density. ...

5

No. Phobos is small - just 11 Km across - the size of a small city. Mars (and Phobos) is so far away that a Phobos impact will not affect Earth much. (Mars ranges from 100 billion meters away to nearly 400 billion meters depending on its and Earth's position in their orbits.) When Phobos hits the Roche limit as it will break up and become a thin light-grey ...

4

Some of the water evaporated, some of it frooze and another good part went into the surface and is now subterranean. For more info read Mars' Vanished Water & Atmosphere --Where Did It Go? and MAVEN’s Quest – Where Did Mars Water Go?. There's much still to learn and experiments in the future will help us to better understand the evolution of mars ...

4

If, Venus had started out at Mars' position, it is possible it would've ended up evolving into an ice giant. At the greater distance of Mars the Sun's solar wind is weaker and would've stripped off much less of Venus' atmosphere, even in comparison to the amount Earth lost, as Earth is considerably closer to the Sun than Mars. So, Venus would perhaps have ...

4

Additionally, Mars has a much more substantial atmosphere composed of ~95% CO2 (which is one of the major points Zubrin makes), whereas the atmosphere of the moon pales in comparison. Why is this important? Combined with the supply of Hydrogen which would be brought along, you could combine the CO2 with H2 to produce methane (CH4) which can be used as rocket ...

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