
Mars Astronauts Likely to Witness 1 Megaton Asteroid Impacts - Libertatea
http://www.technologyreview.com/view/508906/mars-astronauts-likely-to-witness-1-megaton-asteroid-impacts/
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troels
_Their model suggests that Tunguska-type events of around 10 megatons should
occur roughly once a century and smaller 1 megaton events once every 15
years._

If the rate is 1/15 years on Earth, why haven't I witnessed any yet? I suspect
the answer is that Earth is rather large. Mars may not be quite as big, but
it's still quite implausible that our Mars visitors should happen to be at
just the wrong place at the wrong time, even with a 5-times increase in risk.

~~~
tgflynn
It seems like if a 1 megaton impact were occurring on Earth every 15 years
people would have noticed more than seems to be the case. You would expect
more than one such event per century to occur on land and I think the vast
majority of the Earth's land is populated, at least sparsely.

Also for the past 50 years or so governments have been very interested in
tracking large explosions so even such events occurring over water should have
been detected and, I would think, mentioned in the media.

~~~
Gravityloss
Yes. This doesn't pass the smell test. I first suspected the article produces
a garbled version of the research, but the abstract says the same too:

<http://arxiv.org/abs/1212.3273>

" In particular, for energies of one megaton or larger we find near one impact
every three years for Mars, an interesting and concerning result for future
Mars explorations. The corresponding calculations for our planet give a
probability of one impact per 15 years"

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debacle
Perhaps the "1 megaton" nomer is for what encounters our atmosphere, not
necessarily what impacts our surface.

~~~
troels
That might be the case, but then it's not really something to be worried
about, is it? I mean, then they're basically saying that astronauts on Mars
will see shooting stars a bit more often than on Earth.

~~~
debacle
It is, because on Mars there isn't an atmosphere there to burn up that 1
megaton asteroid into something more innocuous.

~~~
danielweber
Just to be clear, Mars does have an atmosphere. It's pretty thin, but it's
real enough to provide protection against micrometeorites and some of the
radiation.

It ain't gonna stop a school-bus sized meteorite, though.

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aptwebapps
When they say one megaton, do they mean total energy released during entry or
something? There's no way we're having the equivalent of a one megaton nuke
(minus the fallout) on the surface every fifteen years ...

Or are we just in a dry patch?

Edit: The actual paper says 'impact' so I don't know what to think here.

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jere
>Here’s the interesting part: these guys calcaulte that Mars experiences a 1
megaton event every three years.

We've had orbiting satellites around Mars for over a decade. Wouldn't they be
capable of seeing such an impact?

~~~
InclinedPlane
We've had launch and nuclear explosion detection satellites around the Earth
for decades and we haven't detected anything like 1 megaton impact event every
15 years.

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lucaspiller
What does this actually mean? Obviously it is pretty obvious if it lands on
top of you, but if there is a 1 megaton impact of a meteorite landing 10 miles
away what are the consequences? Given the lower gravity and atmospheric
pressure would you be basically sand blasted with remnants?

~~~
arethuza
Using some online calculators for the effects of nuclear weapons, I suspect
the answer would be that you'd be reasonably safe at 16km:

[http://www.alternatewars.com/BBOW/ABC_Weapons/Nuke_Effects_C...](http://www.alternatewars.com/BBOW/ABC_Weapons/Nuke_Effects_Calculator.htm)

<http://meyerweb.com/eric/tools/gmap/hydesim.html>

I don't know if a meteor impact would produce the same prompt radiation as a
H-bomb, but the much less dense Martian atmosphere might negate that.

~~~
tgflynn
Most of the ionizing radiation from an H bomb is produced by nuclear fusion or
from fission from the trigger and decay products. An asteroid impact wouldn't
produce any of that. The only ionizing radiation it might produce are some
x-rays from the fireball plasma (but I'm not sure the plasma would even be hot
enough for that).

The blast and thermal effects would presumably be comparable, however, so at
16 km you'd definitely notice (and might be in a very uncomfortable
situation).

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danielweber
_Nevertheless, these kind of predictions require further study._

There's the money quote. Quite literally.

There are all sorts of people who see the path to Mars littered with bags of
money and are quite happy to insert themselves into the path.

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andyjohnson0
First sentence: _"Asteroid impacts are among the most feared of natural
catastrophes."_

Maybe I'm being picky, but I don't think that this is actually true.

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pavel_lishin
The word "among" makes it a pretty subjective thing.

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mkelley
Ok so what is that in Hiroshimas?

~~~
nakedrobot2
According to 10 seconds googling, little boy and fat man were both somewhere
around 20 KILOtons.

