Comet To Make Close Call With Mars

sciencehabit writes In mid-October, a comet sweeping through our inner solar system for the first time will pass near Mars—so close, in fact, that if it were buzzing Earth at the same distance it would fly by well inside our moon's orbit. While material spewing from the icy visitor probably won't trigger the colossal meteor showers on the Red Planet that some scientists predicted, dust and water vapor may still slam into Mars, briefly heating up its atmosphere and threatening orbiting spacecraft. However it affects the planet, the comet should give scientists their closest view yet of a near-pristine visitor from the outer edges of our solar system.

Comments

First pass

[Thanshin]

I don't understand the concept of first pass. Do they really mean "first pass ever" which I suppose would also mean humanity will never ever interact with this comet ever?

Or is it "first pass since we are able to see them, but it's part of the Solar System and it will eventually come back.

Re:First pass

[tonique]

The theory is that there's a big (really big) store of comets in Oort's cloud on the far outskirts of the solar system. They have never been near to the Sun having been formed far from the centre. Once their movements are perturbed they may go towards the Sun.

It really may be the first pass ever.

Re:First pass

[jovius]

I hope it does the second pass for better quality at least.

Re:First pass

[somegeekynick]

I don't understand the concept of first pass. Do they really mean "first pass ever" which I suppose would also mean humanity will never ever interact with this comet ever?

[emphasis mine] Why? (Assuming humanity lives in harmony on Earth for another few million years) It's non-periodic (the 'C' in C/2013 A1 (Siding Spring)) comet, so as far as we know, it will be the first and only pass through the inner Solar System.

Re:First pass

[Anonymous Coward]

They have meant 'first post' you insensitive clod, but they needed to bypass the lameness filter.

Re:First pass

[Sockatume]

Can I take a moment to talk about how mind-crushingly vast the Oort cloud is? It doesn't begin until something on the order of 100 times the orbit of the furthest known dwarf planets, and then it goes out about a quarter of the way to the nearest neighbouring star. It's so far away that, being composed of inert space junk, we have no direct observational evidence of its existence. I mean, space is big, big to the point where thinking hard about Jupiter makes my temples ache, but the Oort cloud is something else entirely. And that's just an object on a planetary system scale!

Re:First pass

[CreatureComfort]

"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."

\ RIP DNA - We miss you.

Too bad this didn't happen in 50 years

[wisebabo]

If this happened (optimistically) 50 years from now, we'd be able to deflect the comet to HIT mars, thus delivering a lot of water and warming things up a bit. (Only, I'm afraid, a little bit of terraforming, it would probably take thousands of such comet strikes to make the planet "habitable"). Or we could make it hit one of the moons and, if done very carefully, could deliver said water to possible Mars Moon colonists (but they'd have to find a way to keep the resulting fragments from ruining near-Mars space for space travels).

More realistically, I wonder if NASA (and the ESA) have plans to move their spacecraft for best viewing. If they're worried about damage, they could have them be on the other side of the planet when it makes its closest approach. If there are any spacecraft that are on their "last legs" (low propellent, malfunctioning equipment, no more spare reaction wheels), perhaps they could even make a very risky close approach!

I expect there will be some great images! (If the HiRes camera on the Mars Reconnaissance Orbiter can take 1m resolutions of Mars from orbit, it surely will be able to take great pictures of a comet only a few tens of thousands of kilometers away).

Re:Too bad this didn't happen in 50 years

[Gothmolly]

Too bad the solar wind will ionize and rip away any atmosphere that accumulates due to 1000s of comet impacts. Mars has no deflector shield like Earth has.

Re:Too bad this didn't happen in 50 years

[Immerman]

So what? You're not going to alter the planet's trajectory enough to be an issue just by throwing a few pebbles at it. Especially if those pebbles are spread fairly evenly across multiple years so that the perturbations tend to cancel each other out. Even if it was just one ginormous impact that is unlikely to necessitate anything more than altering a few decimal places in the orbital parameters to keep our planetariums accurate.

Remember - both Earth and Mars have been hit by truly *massive* bodies in the distant past - in our case it knocked off enough material to form the Moon, In Mars's case it formed Olmypus Mons on the opposite side of the planet from a basin spanning a good portion of the hemisphere. And yet both planets have almost perfectly circular orbits (yeah, they've no doubt been circularizing ever since, but still).

Plus, if you don't slam the comets into the surface, how are you going to add their water to the planet? Warming the planet substantially with cometary friction heating is a fool's game - the real gains come from increasing the density of CO2 in the atmosphere so you can capture more solar energy. IIRC on Earth the CO2 from burning a single gallon of gasoline will capture something like 1,000,000x as much solar energy as was generated in the initial combustion before it gets recaptured, and without oceans or plant life I'm betting the Martian carbon cycle is *far* slower. Perhaps we could find some asteroids rich in carbon and oxygen and shatter them just before hitting the Martian atmosphere so that the whole thing burns up in the atmosphere, adding a bunch of fresh CO2 and kick-starting a little intentional global warming.

Slingshot?

[inAbsurdum]

Has anyone calculated what effect Mars's gravity will have on the comets trajectory? Will it gain/lose velocity relative to the sun? Will it's orbit be narrower/wider (will the close encounter send the rock tumbling out of the system again, or will it smash into the sun)? Or will the forces involved be simply too small to have the tiniest effect?

Re:Slingshot?

[Immerman]

I think comets tend to be moving far to fast for a gravitational slingshot to have much effect. Your basic gravitational slingsot involves a near-miss head-on collision with a planet racing towards you. You whip around the planet and fly back roughly the way you came with your initial speed plus the orbital speed of the planet. Obviously you can do a less dramatic maneuver, but you only get a fraction of the speed boost.

Comets meanwhile have typically been falling towards the sun from a good portion of a light year away, and are moving far, *far* faster than the planets, so even an ideal slingshot maneuver wouldn't alter their speed much, relatively speaking. At most their path gets deflected so that they leave the inner system with a very different trajectory than they entered with, rather than heading back out pretty much the way they came, essentially rotating the major axis of their orbit. But their orbital energy, and hence the basic shape of their orbit, remains largely unchanged. Unless of course it hits something, but that's a matter of hitting one of a few dust motes in an Olympic stadium, and is highly unlikely for any given comet.

In the case of periodic comets (those whose highly elliptical orbits will eventually bring them back into the inner system) you can have cumulative effects, especially if it happens to have an orbital resonance with one of the planets. And over the course of several orbits it's possible for gravitational effects to "fine tune" it's path in ways that increase the odds of a collision. But I believe this comet is on a parabolic path rather than an elliptical one (considerably higher orbital energy), so unless it hits something on this pass (or evaporates) it will slingshot around the sun and then depart to interstellar space, never to be seen again.