Mars has a gravitational binding energy of ~5x10^30 jouleS. If a bomb went off on mars that released that much energy, how much danger would the earth be in. Additionally, would debris striking earth be a major concern?
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5$\begingroup$ That energy just makes a cloud of just-unbound matter. To send it somewhere else requires more energy. $\endgroup$– Jon CusterDec 25, 2022 at 17:38
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$\begingroup$ if instead of a bomb, it was a light, earth would receive about as much light as 3 hours of sunlight $\endgroup$– amaraDec 25, 2022 at 18:34
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1$\begingroup$ Depends upon the bomber's intent. Clearly they have demonstrated the capability to destroy a planet if they so choose. $\endgroup$– user535733Dec 26, 2022 at 5:13
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$\begingroup$ If the explosion was spherical, I'd expect not much earth effect. If the explosion was circular, I'd expect a significant earth effect if aligned near both orbits. $\endgroup$– chux - Reinstate MonicaDec 26, 2022 at 12:47
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1$\begingroup$ depending on the energy of the explosion, it is also possible that the parts of Mars fall back towards each other, eventually creating a planet again $\endgroup$– njzk2Dec 26, 2022 at 12:55
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3 Answers
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The only danger for Earth from such an event would be related to bombardment caused by the fragments resulting from it.
However, how big would these fragments be? Well, if you are releasing that much energy in a single shot, I doubt you would be getting anything bigger than dust/pebbles.
Of them, there would be a small fraction on a direct trajectory toward Earth, another fraction which would end up hitting Earth after a few swings around the Sun and other planets and what I suspect would be the largest fraction which will never make it to Earth. Considering that even the parts hitting Earth would not get here in a single go, I don't think we should worry too much.
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4$\begingroup$ What about changes to Earth's orbit (and the asteroids) due to the redistribution of mass? How much effect does Mars' gravity have? $\endgroup$ Dec 25, 2022 at 13:42
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3$\begingroup$ @FlaStorm32, the n-body-problem (for n in the hundreds or thousands) is notoriously hard to solve. A large fragment or many little ones doing a slingshot maneuver would affect Earth orbit a tiny bit, but another fragment might have the opposite change. $\endgroup$– o.m.Dec 25, 2022 at 14:09
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2$\begingroup$ Have we got any data/theory on the distribution of the size of the resulting fragments? I know that space is big. Really big. But so is Mars. Think of Mars as a cube with 5000km side length (it is a bit bigger, but let's use this as a ball park figure). Chicxulub asteroid was estimated to have diameter about 10 km. So Mars has material for 125 million Chicxulub sized chunks. I'm somewhat uncomfortable with the thought of all of those circling in the neighborhood. I know, this number is based on Mars getting sliced "thinly" with surgical precision but anyway. $\endgroup$ Dec 25, 2022 at 20:27
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Life on Earth would be significantly disrupted, but might recover within a few hundred million years.
Assuming the mass of what used to be Mars is spread evenly over the interior of a sphere with the same radius as what used to be its orbit, Earth would sweep out a volume of debris with a mass of 3*10^15 kg each year. This represents a billionfold increase over the amount of space dust that currently lands per year. Or, alternatively, it's three times the mass of the asteroid that killed the dinosaurs - but landing as a continual sandblasting over a year, rather than one big hit.
By colliding with the atmosphere at Earth escape velocity, the Mars dust would heat it up somewhat; an average of 36 watts per square meter over Earth's leading hemisphere, day and night, strongest at sunrise. This is quite a bit less than solar irradiance, which is 1380 W/m^2 when the sun is overhead, but would be noticeable and would increase global temperatures.
Depending on the distribution of particle sizes, quite a few would make it to the surface, causing damage to crops, buildings and vehicles, starting forest fires, and killing people and animals. Death by meteorite would go from a freak occurrence to an everyday event. Life at altitude would carry significant hazards, stratospheric flight would become intensely hazardous, and spaceflight all but impossible; no more satellites for communication or Earth sensing.
The amount of Mars dust landing - 6kg per square meter per year, mainly composed of iron and nickel - would cause significant disruption to ecosystems. Worse, it would oxidize in the atmosphere, removing oxygen; this would not be noticeable at first, but within 1000 years vertebrate life would be in severe difficulty. One large unknown is the extent to which aerosols would form in the troposphere, and the resulting dimming and cooling effect; this could cause a "volcanic winter" style disruption to plant life, again similar to the K-T impact event.
As time went by, impact events would worsen significantly, initially from asteroids liberated from the asteroid belt by the absence of Mars's shepherding influence and by disruption caused by frictional braking from Mars dust, then later by asteroids accreted from Mars dust itself. More impactors would make it through to the Earth's surface, causing localized damage and global aerosol cooling. Terrestrial life would be all but wiped out, but life would continue in the oceans.
Eventually the skies would clear and life could move back onto the land... but it had better hurry, because in a billion years the Sun will become too bright for Earth to remain habitable.
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13$\begingroup$ Huge unjustified assumption in the first sentence - why are you assuming that all of the mass would be evenly distributed inwards? Are you assuming it's all in the plane of the ecliptic or is it filling the sphere? It it's been distributed in all directions then at least as much will be heading towards Jupiter's orbit. The consequences of Earth ploughing through a permanent dustcloud make sense, but having all of ex-Mars' mass forming a dustcloud conveniently located to sandblast Earth does not. $\endgroup$ Dec 26, 2022 at 0:28
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1$\begingroup$ @KerrAvon2055 To go further, if we assume that Earth subtends a 1 degree angle from Mars, then it seems that 359/360 of the debris would blast out at an angle which misses earth entirely, by being "above" or "below" the ecliptic. Of course Earth actually subtends are far smaller angle than 1 degree, so the vast, vast fraction of the blast will be entirely out-of-plane of Earth's orbit. The vast majority of what's in-plane will cross our orbit when Earth is elsewhere, leaving an infinitesimal fraction to hit the atmosphere. I agree that "even distribution inwards" seems very unrealistic. $\endgroup$– Ralph JDec 26, 2022 at 5:05
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1$\begingroup$ @KerrAvon2055 I don't know how these 3*10^15 kg where computed exactly but note that the mass of Mars is around 6*10^23 kg so this does assume that only a tiny fraction of the mass ends up in Earth orbit. The answer does however assume that these 3*10^15 kg happen every year for a long time instead of only once which seems odd to me. $\endgroup$– quaragueDec 26, 2022 at 6:47
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2$\begingroup$ @KerrAvon2055 The assumption isn't that huge. 1) Outward vs. inward will be roughly 50:50, i.e. this answer exaggerates the impact by a factor of 2, which is a lot but does not change the outcome much. 2) Stuff outside the ecliptic will be shepherded into the ecliptic, eventually. Given the timeframe, it's not too unreasonable to assume that most stuff will end up hitting some inner planet, and given planet sizes, Earth will indeed sweep up most of it. $\endgroup$ Dec 26, 2022 at 9:11
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2$\begingroup$ @toolforger the issue is what will be the timeframe. The answer doesn't include enough information to understand how this number is obtained $\endgroup$– njzk2Dec 26, 2022 at 12:52
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Here is a link to a similar question about what would happen to Earth if Pluto exploded.
In my answer I conclude that:
So exactly how the aliens get rid of Pluto could determine whether nobody on Earth notices it for weeks or months at one extreme, or all life on Earth dies out within a few months on the other extreme.
The mass of Mars is about 0.107 Earth masses, and the mass of Pluto is about 0.00218 Earth masses, so Mars has about 49.08 times the mass of Pluto. The average distance between Pluto and Earth is about 39.482 AU, while the average distnce between Mars and Earth is about 1.523 AU, so Pluto is about 25.923 times as far from Earth.
Thus when the cloud of expanding debris from Mars reaches Earth it should be about 25.923 cubed, or 17,420.306 times as dense as the debris cloud from an exploding Pluto, times 49.08 for the greater mass of Mars, for a total of 854,988.6188 times as dense as the debris cloud of Pluto.
But Mars sometimes is only 0.3727 AU from Earth, making Pluto about 105.935 times farther. So a Martian debris cloud expanded far enough for Earth to pass through it at the closest opposition of Mars would be (105.935 X 105.935 X 105.935 X 49.08), or 58,347,595.95 as dense as a Pluto debris cloud reaching Earth.
So if there is any possibility of a Pluto debris cloud harming Earth there would be a much greater probabiilty of a Mars debris cloud harming Earth.
There is an Endor Holocaust theory, claiming that the explosion of the second Death Star would probably wipe out all life on Endor in a relatively short time.
And someone might also have a Yavin Holocaust Theory, speculating whether all life on the moon of Yavin would have been destroyed by the explosion of the first Death Star.
My answer at this thread:
speculates about the distance between the Death Star and Yavin when it was about to fire on Yavin.
And maybe someone should think about a Death Star Holocaust Theory, calculating whether the first Death Star was too close to Alderaan and whether it would have been destroyed by the wreckage of its planetary victim.
answered Dec 26, 2022 at 2:20
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1$\begingroup$ Endor isn't applicable, it's so catastrophic because the Death Star is slow and close, i.e. all its mass is hitting the moon within a day. Mars debris would hit Earth over a MUCH longer time, let alone Pluto. Pluto debris would also be mostly sweeped up by Jupiter and Saturn. $\endgroup$ Dec 26, 2022 at 9:26