What would happen if another planet (say mars) collided into earth?

Factual Questions
1

Ok, basic reasoning says it won’t happen, but lets hypothesise that somehow mars lost its orbit, and hurtled towards earth at a similar speed to what it does now. It is going to collide dead on with the surface of earth.
What would it look like from ground zero? Would earth or mars be destroyed? Would they just bounce off each other? What would be the gravitational effects for people on earth? Would some people survive? What about gravity; would it be permantly screwed up?

I’ve been thinking about this question for a while, there’s a few hypothesis gurus on this forum so why not ask :cool:

2

Use this Meteor Collision Calculator to find out.
The diameter of Mars is about 6800km.
When you get the results, be sure to compare the diameter of the resulting crater to the 12,700 km diameter of the Earth.

3

OK, from a geologist without protfolio, and I’m sure you’ll get more accurate and detailed answers, but in the meantime:

It would actually be quite difficult to get them to smash into each other like two billiard balls. Firstly, of course, you’ve got to get Mars on a collision course with Earth. About the only way one could do that would be if some massive body passed close enough to Mars to throw it out of its current orbit, into one that might intersect with that of Earth’s. Then you’d have to wait, probably a very long time indeed, until Mars and Earth came close enough in their respective orbital cycles that the interaction of their masses had a significant effect on each other. Even then the most likely scenario would be a near miss, with Mars and Earth heading off into new orbits that may or may not (probably not) intersect again.

A reddish moon getting bigger and bigger…

In all cases where the planets came into actual contact with each other, both would be altered to the point that one might as well say they were destroyed, even if both were left with most of their original mass after the collision.

Depends on the speed of impact and whether the impact were direct or glancing. For a direct impact, I would think the greatest likelihood would be a high-velocity collision that would eject huge amounts of debris, with the remnants of the planets continuing on in significantly different orbits.

Increasing tides and greater earth movements as Mars approaches within maybe three or four times the diameter of the Moon’s orbit. Once Mars gets within Moon distance, really high tides and massive earth displacements, I guess. One smarter than I could calculate the gravitational effects of a Mars-sized body at a distance less than that of the Moon, but at that point one would have probably less than 24 hours to observe those effects before all humanity was obliterated in the impact.

It is highly unlikely, IMO, that any point on the surface of the Earth would be unaffected enough by the strike that anyone could survive.

Gravity doesn’t get ‘screwed up’; what you would have would be the gravitational effect consistent with whatever mass Earth was left with after the strike.

4

This is just a WAG, of course, but…

It seems to me there’s no good ending to an earth-mars collision, no matter how ya try.

If they ‘crash’ into each other, according to squink’s link, it’s total destruction… I figure there’s a new asteroid belt.

But if they’re going slowly enough, that’s where it gets interesting.

Imagine a scenario in which Mars comes creeping up… closer and closer, year by year, over, say, a century or two.

There’s going to be a point, long before the two bodies come anywhere near one another, where their gravities will begin affecting one another rather noticeably… you think the moon’s tides are somethin’? Mars-tides would be rather larger.

Mars is a cold dead planet, from my understanding. Earth isn’t… earth, in fact, is mostly liquid. So as Mars started getting closer and closer, the tidal forces would pretty much rip the mantle to shreds, by affecting the magma beneath.

Nobody would live to see it when, years later, mars finally plunges into the violently heaving mass of molten rock that used to be the earth… but wow, what a view if you did! And found somewhere to sit, I suppose. :eek:

5

No, Mars is still quite active volcanically.

6

Last time it happened, we got the Moon.

7

Apparently, the scenario already happened …

Source: http://www.newton.dep.anl.gov/newton/askasci/1995/astron/AST082.HTM

8

Current theory does suggest that the Earth WAS hit by an object roughly the size of Mars a couple billion years ago. The material ripped out; along with material from that object then formed the moon.

9

There an echo in here?

10

Quack!

(just checking)

11

Quack!

12

Since we don’t have any file footage of the previous Mars-sized collision, we have to go with the computer models, which showed that a run-of-the-mill Mars-sized collision would not have created the moon–that it would have taken an extraordinary glancing double-hit sorta thing would have done it.

Possibly that was mentioned in one of the links from the “Nature” link.

13

By the way, yer right QED (of course).

I was certain that mars was volcanically dead, but you inspired me to actually research my point, and yer right… plenty of sources saying it’s at least recently active, and therefore probably still is, popped right up with a simple googling.

Learn somethin’ new every day! ;j

14

Roland Emmerich or Jerry Bruckheimer would make a movie about it.

15

http://www.lpl.arizona.edu/impacteffects/

16

If mars collides with the waterly body like earth then there will be water of mars and it will be habitable for humans to live on it

17

Unlikely. The energy of the impact would be so vast that much of the water of the Earth would boil off into space, and very little would settle back onto the remnant of Mars. Last time it happened we ended up with a very dry Moon, and the Earth’s surface was red hot for many thousands of years.

18

If Mars collides with Earth, there won’t be any humans (or any other life, for that matter) left.

Also, as mentioned earlier in the thread (back in 2004!), one hypothesis for the creation of the Moon was the collision of a Mars-sized object with the Earth. The resulting body (the Moon) has no water to speak of.

Finally, you need more than just water for life. You also need a planet to have a stable orbit in the habitable zone of a star, and the planet needs to be massive enough to hold on to an atmosphere (but not so massive as to result in a gas giant planet).

19

Wow, great link, thank you.

It shows that a body just 50 km in diameter would cause an impact equivalent to a 7 billion megaton bomb, causing an earthquake of magnitude 12.2, and throwing enough dust into the atmosphere to make the planet very cold for many years, causing a mass extinction event, including humans. And a body about 325 km would cause the oceans to boil.

Which, I guess, would help mitigate the freezing cold from the dust.

20

Obligatory Frank Sinatra quote:

Have you heard, it’s in the stars
Next July we collide with Mars
Well did you evah
What a swell party
A swell party
A swellegant, elegant party this is