Chance for a Tunguska Sized Impact on Mars

Multiple users have written to tell us of an LA Times report that an asteroid may hit Mars on January 30th. The asteroid is roughly 160 feet across, and JPL-based researchers say that it will have a 1-in-75 chance of striking Mars. Those odds are very high for this type of event, and scientists are hoping to witness an impact of a similar scope to the Tunguska disaster. From the LA Times: "Because scientists have never observed an asteroid impact -- the closest thing being the 1994 collision of comet Shoemaker-Levy with Jupiter -- such a collision on Mars would produce a 'scientific bonanza,' Chesley said."

It'd be so awesome

[QuantumG]

We'd be talking about it for decades. It might actually wake up some people to the NEA threat to our own planet. It might have a devastating and instant effect on the atmosphere of Mars.. which could actually make the planet a little warmer and a little more hospitable.

And if it doesn't hit...

[CubicleView]

Even if it misses it should still be a little interesting. If it comes that close, its orbit will be greatly affected, observing the results should be useful?

For their sake I hope it happens, but...

[lpangelrob]

...if an Tunguska-sized impact occurs on the side of the planet we can't see, did it really happen at all?

New rover mission?

[Xelios]

If the asteroid does hit the impact site would probably make for a good rover mission. Fresh samples of long buried rock without the extra hassle of having to dig it up!

The question is

[maroberts]

How long would it take to get to the impact site, bearing in mind that it travels at an average speed of 1cm per second, and that dust in the atmosphere from the impact will probably drastically reduce it's recharge ability?

I think you'd get there quicker by launching another rover mission!!

Why?

[WindBourne]

If this was venus, I would love to see it impact it, but it would be better if it was not mars. The reason is that it will lead to "nuclear winter". Mars is already cold and does not need more. If we have any chance of colonizing this planet, it will be only if it warms up. In addition, with lots more dust in the air, any future exploration vehicles will require nuclear power. Of course, if hits one of the poles, it might just melt all the CO2. Hmmmmm.

It would be interesting to see venus be hit. If that happened, it might just cool down the planet a bit. Of course, I suspect that it it would take a pretty big one

Re:Occluded for 2 weeks??? Bull****

[Ponderoid]

If it's gonna take two weeks to get enough observations in to pin down its orbit, fine. Throwing in the fact there happens to be an occultation somewhere in there, which will last, what, an hour at most? That confuses the issue to the lay public. It's irrelevant for refining the asteroid's orbit. The article makes it sound like the asteroid will be hiding behind the moon for the entire period, when that can't possibly be the case.

*** Ponder

It won't be the same.

[Anonymous Coward]

The received wisdom used to be that the meteorite, that caused the disaster in Tunguska, exploded above the surface of the earth. It entered the atmosphere at a relatively shallow angle and heated up much more than it would have if it had come straight down. The result was that a long relatively narrow area of forest was knocked down and there was no impact crater.

On Mars, the atmosphere is much less dense than that of the earth. The meteor in question is large. If it hits Mars, it will reach the surface, it won't vaporize in the atmosphere. The result will be much more like other impacts on the earth that did leave craters. In that light, the comparison with Tunguska doesn't make much sense. I don't know where Steve Chesley got his information on the size of the rock that exploded over Siberia but I bet it wasn't 160 feet across. Something that size would make it to the Earth's surface.

Are folks forgetting the relative lack air on mars

[Almost-Retired]

I'll bet they are. Because we have this nice dense atmosphere to sustain our breathing, we tend to forget that mars has only 2 or 3% of the surface air pressure to heat and absorb energy from an incoming rock like we have. The damage will be from a direct surface hit at the rocks full speed and should be visible if it hits on our side of mars, and it will no doubt toss up a few megatons of ejecta, which due to the speed of the wind, will take a while to settle. That does have the possibility of finishing off the rovers. There is a slim chance some of the ejecta may even make it to earth and be found on the antarctic snow eventually, giving us a few more samples of our neighbor to study.

If it hits where we can see it, it should be quite a show and I hope they have a good number of our telescopes, even Hubble, recording like crazy.

I guess we'll find out January 30th. But if its on the far side, we may have to do before and after photo comparisons to find the crater once the dust has settled, and that won't be near as informative as a near side hit would be.

Humm, recently the chinese were accused of doctoring a moon photo. Makes me wonder if the moved crater might in fact be a new one?

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
  soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
10) there is no 10, but it sounded like a nice number :)
                -- Wichert Akkerman

Re:Why?

[QuantumG]

That's the funny thing about mega-events in chaotic systems, you never know what might happen.

Re:Occluded for 2 weeks??? Bull****

[Ponderoid]

It just occurred to me that the astronomer being quoted might not have been referring to an occultation at all. That's a pretty rare event for any given asteroid. It's possible that the astronomer was referring to needing to wait for the bright moon to get out of the sky at the same time the asteroid is up, which can take a week or more, depending on its current phase. The extra extinction caused by a bright moon might be enough to prevent the detailed observations needed to get a good orbital fix on the asteroid. This still doesn't excuse the lousy science reporting, which flat-out declared the asteroid was behind the moon, and implied it would remain there for two weeks.

*** Ponder

Re:dust in the atmosphere

[Hotawa Hawk-eye]

I think they'd be less worried about the loss of communications than about the fact that the dust will block sunlight from reaching the rovers' solar panels. If they lose communications with the rovers for a while, there's still a chance to restore that communication. If the rovers lose power, it may not be possible to restore communication with them (short of having future manned Mars missions seek them out and jump start them.)

I wonder if NASA has AAA service [wikipedia.org] -- that would be one hell of a service call. "Hello, yes, our batteries are dead and we need a jump start. You'll never guess where we are ..."

Re:Bad for studying Mars?

[iamlucky13]

We have most definitely tested nuclear weapons on, above, and below the ground [wikipedia.org]. The Trinity test was only about 100 meters above the ground and kicked up a fair amount of dust, but it definitely did not spread globally.

The impact, should we be fortunate enough to witness one, will no doubt kick up a huge amount of dust over an area of a couple dozen square miles. However, the total energy of this impact is likely to pale compared to even a modestly sized dust storm, and as the cloud spreads out over thousands of square miles, the opacity will drop quickly.

NOAA says that a fully developed hurricane releases 10 megatons of energy every 20 minutes. The storm Opportunity and Spirit endured a few months ago was lower intensity but far, far larger in scale than a hurricane, and it lasted for weeks. Opportunity, fortunately, had a stiff breeze later blow a lot of the dust off its solar panels and is in great shape. Spirit less lucky at the moment, but its happened for both of them multiple times in the past, and may well happen again.

So unless it were to hit near enough to dump substantially sized debris on one of the rovers (it sounds like Opportunity's side of the planet will be facing when it passes), the odds of survival seem pretty good to me.

If it does hit, it will be a fantastic opportunity for observing the effects of impacts on a rocky planet (remember how excited the astronomy community was when Shoemaker-Levy 9 hit Jupiter a few years back?), and we're well equipped to observe it in detail. First of all, Mars is nearly at it's closest approach to earth, so viewing from Hubble and ground scopes will be optimal.

Secondly, as mentioned the rovers may be able to observe the entry and impact. They could also measure the opacity of the debris cloud and how it spreads, and perhaps even measure some of the minerals thrown up using the Mini-TES instrument.

Third, there are three orbiters operating around Mars at the moment. All of them have pretty decent cameras on them to study before and after pictures of any crater, watch the debris cloud expand from above, and perhaps even fly through the debris to sniff it out and look for clues of buried water thrown up by the impact. Mars Express and Mars Reconnaissance Orbiter both have spectrometers that may be useful for that, and a couple of climate instruments that can investigate the effects on Mars atmosphere. The science teams may also come up with some clever ways to get bonus science, too. For example, when Cassini flew through the outer rings of Saturn, NASA measured the density and size of the ring particles by recording bursts of radio noise generated as tiny bits of dust vaporized against her high gain antenna.