Phobos

[tejolson]

Phobos is going to collide with Mars at some point. We should speed up the process. I imagine there is some serious scientific data that can be gathered by having a close up of a large impact like that. Maybe tectonic plates can be formed. I imagine we can use the gravity of another planet to send a missle at it fast enough to change Phobos's trajectory.

 

[MeteorWayne]

Definately in the wrong forum; check the Moderator Actions discussion above to find it once we decide which is the best place.

 

[tejolson]

How bout Apophis? We slap some rockets on it and accelerate it into Mars! That should get the electromagnetic field kick started. Oh, and make sure we also put a camera on it with some messuring instruments. Camera is the most important part though, that footage would be so cool. In 3D also.

 

[Boots09]

Is'nt mars without a magnetic field due to the core being cold/dead ? If so don't think an astroid strike could heat it back up. Be cool to see though..

 

[kristina3313]

Great, one less thing to pack while going to Mars... a compass :lol:

 

[Gravity_Ray]

I dont think people sometimes realize just how big a planet is!

You can slam Phobos into Mars all day long and add a couple of Apophis in there for good measure and still you wouldn’t get either tectonic movement or melt the core to start a magnetic field. It may thicken the atmosphere a bit, but that’s probably about it.

It would be good show though.

 

[Mee_n_Mac]

Phobos is going to collide with Mars at some point. We should speed up the process. I imagine there is some serious scientific data that can be gathered by having a close up of a large impact like that. Maybe tectonic plates can be formed. I imagine we can use the gravity of another planet to send a missle at it fast enough to change Phobos's trajectory.

Just to expand on G_R's thoughts ...

You'd need an awfully big missile/rocket to affect Phobos. And given that just think about how big it would have to be on the launch pad. Using a lot of rockets would decrease the size issue but that would still be more mass (in total) than can be done with present technology. Consider that only a fraction of the momentum from all these rockets would actually be transferred to Phobos. You'd be much better off setting up a mass driver on Phobos and tossing pieces of it offworld to affect it's orbit.

 

[SJQ]

If we decide that are going to impact Phobos into Mars (for any reason), then yes, a mass driver on Phobos is the way to go. Question: which is more efficient -

a) launching the mass tangentially into the direction of Phobos' motion?
b) radially, outward from Mars?
c) some combination of a) and b)?

The first choice is classical physics, reducing momentum until Phobos noticeably interacts with the Martian atmosphere (things change then, but Phobos is committed to impact for sure). The second choices moves the existing orbit in plane (I don't think it changes the net orbital momentum of Phobos, at least not significantly) such that Phobos periodically interacts with the Martian atmosphere sooner, and at higher speed (drag varies with the square of the velocity, as I recall - could be wrong on that).

Yes, I know the Martian atmosphere is thin, and aerobraking has been useful for only small payloads, but we don't need to de-orbit Phobos in a single pass, or even a few thousand orbits. At some point, tidal stresses will break Phobos up, changing the orbital mechanics and aerodynamics considerably (and causing lots of big holes, rather than one immense one in the surface of Mars), but for simplicity/first approximation, ignore this.

Supplemental question: Given the low approach angle and (comparatively) low relative velocity, how likely are "round" craters to form? Is the approach angle shallow enough to stretch the craters down-range?

 

[csmyth3025]

Regardless of how we propose to change the orbit of Phobos, we need to consider the monumental scale of such an undertaking.

The mass of Phobos is estimated to be 1.072*10^16 kg according to Wikipedia. Suppose by some extraordinary effort we were able to position the first stage of a Saturn V rocket on Phobos and fire it up. The first stage of a Saturn V weighs in at 2.3 million kg, of which about 130,000 kg is the first stage assembly itself and about 2,170,000 kg is fuel. Wikipedia lists the burn time for the Saturn V first stage as 150 seconds in the specification block of their article and as 168 seconds in the article itself. We'll go with 168 seconds.

The thrust produced by the five F-1 engines of the first stage of the Saturn V is listed by Wikipedia as 34.02 million Newtons. If we fire the first stage for the full 168 second burn time we'll alter the velocity of Phobos by 18.8*10^-9 m/s if my calculation is correct. That's less than 20 billionths of a meter per second!

I'm not a rocket scientist so I urge someone to check my calculation and verify that it's correct.

Chris

 

[tejolson]

Mars's core is cool, cool being a relative term when compared to Earth (from what I understand). Which means it is still hot down there, but not hot enough. The electromagnetic field is present, it is just weaker than what the planet needs to reflect harmful radiation. We can probably use the field for protection it if we go low enough.

A bombardment in the past caused the electromagnetic field to cease. I do no understand the mechanics. It seems some part of the core was exposed and heat was lost? Is that where the super valcano is? Speaking of the super valcano.... It's a really big valcano, does it have a direct route to the core?

There would be a huge amount of heat and pressure if we crashed Phobos into Mars, or Apophis into Phobos and Phobos into Mars, or just Apophis into Mars. Too bad the CTBT includes all environments. That would be an interesting use of an H-Bomb.

 

[yevaud]

A bombardment in the past caused the electromagnetic field to cease.

Well, no, that's incorrect. The geomagnetic field of Mars is weak as the core is much smaller than Earth's (e.g. lost heat much faster), and it's likely there are fewer radionuclides to heat the core, as occurs here with Earth.

I do no understand the mechanics. It seems some part of the core was exposed and heat was lost? Is that where the super valcano is? Speaking of the super valcano.... It's a really big valcano, does it have a direct route to the core?

Unlike Earth, where we have most volcanoes due to tectonic activity - they occur near or on subduction zones - on Mars they are all "hot spot" volcanoes similar to the Hawaiian Islands. Although, FYI, we know of precisely one major volcano on Mars, e.g. Olympus Mons.

There would be a huge amount of heat and pressure if we crashed Phobos into Mars, or Apophis into Phobos and Phobos into Mars, or just Apophis into Mars. Too bad the CTBT includes all environments. That would be an interesting use of an H-Bomb.

That wouldn't re-activate a senescent core; it'd fill the atmosphere with soot and particulates though.

 

[SJQ]

Mars's core is cool, cool being a relative term when compared to Earth (from what I understand). Which means it is still hot down there, but not hot enough. The electromagnetic field is present, it is just weaker than what the planet needs to reflect harmful radiation. We can probably use the field for protection it if we go low enough.

A bombardment in the past caused the electromagnetic field to cease. I do no understand the mechanics. It seems some part of the core was exposed and heat was lost? Is that where the super valcano is? Speaking of the super valcano.... It's a really big valcano, does it have a direct route to the core?

There would be a huge amount of heat and pressure if we crashed Phobos into Mars, or Apophis into Phobos and Phobos into Mars, or just Apophis into Mars. Too bad the CTBT includes all environments. That would be an interesting use of an H-Bomb.

Mars core is cooler than Earth's, largely because Mars is significantly less massive, and therefore cannot hold heat as well (there are other factors, but I believe this to be "the big one"). The current state of Mars' core is not conclusively known, but the lack of a fluid conductive layer to the core, similar to Earth's outer core, ensures that there is not a geodynamo in operation. Whatever magnetic field is now present on Mars is a residual field, not an actively-generated one. As such, the remaining field is not all that large: even on the surface of Mars, it is too weak to provide any serious protection; in contrast, the Earth's field provides protection out to low Earth orbit.

I suppose it is possible that the bombardment that created the northern plains removed enough of the Martian crust to measurably reduce the Martian magnetic field faster, but it would not do so directly: less crust means less insulation and mass, therefore faster cooling, thus the geodynamo fails sooner. But the act of bombardment would add heat, albeit short-term only, keeping the planet somewhat warmer in a temporary and localized fashion. The cooling came later.

Volcanoes (Mons Olympus and the rest) are not causes of core heat, they are results of core heat - bringing magma to the surface of Mars is simply another way to remove heat from the core. As for providing a "direct route to the core", this is exceedingly unlikely - any remaining magma, still molten, would fill in the pipes leading to the volcano, filling them and then freeze solid.

Impacting Mars with any of the available moons would not provide the necessary heat to melt the core; all you'd get is a large but comparatively shallow hole in Mars, much bigger than any H-bomb could create. Mars is a small planet, true, but it is extemely large compared to Phobos. Any impacting body big enough to melt the Martian core would break up Mars entirely first - it would be a replay of the scenario currently thought to have created Earth's Moon.

 

[yevaud]

Any impacting body big enough to melt the Martian core would break up Mars entirely first - it would be a replay of the scenario currently thought to have created Earth's Moon.

Well, almost. Any body large enough to shatter a planet would have to be either as large/massive as the body it impacts, or have to be moving at one hell of an impact velocity. This is due to the Gravitational Binding Energy of a planetary body[super]*[/super]. The impactor that spalled the Moon off the early Earth was a bit smaller, possibly Mars sized (as current theory believes). But it didn't exceed the Binding Energy of Earth.

In any event, you're correct that anything massive enough or impacting fast enough to significantly heat the core of Mars would surely disarrange the planet to no end.

[super]*[/super]Gravitational Binding Energy for a Planet - For a spherical planet of uniform density:

U = 2GM[super]2[/super] / 5R

G = Gravitational Constant
M - Mass of the spherical body
R = It's radius

 

[SJQ]

Any impacting body big enough to melt the Martian core would break up Mars entirely first - it would be a replay of the scenario currently thought to have created Earth's Moon.

Well, almost. Any body large enough to shatter a planet would have to be either as large/massive as the body it impacts, or have to be moving at one hell of an impact velocity. This is due to the Gravitational Binding Energy of a planetary body[super]*[/super]. The impactor that spalled the Moon off the early Earth was a bit smaller, possibly Mars sized (as current theory believes). But it didn't exceed the Binding Energy of Earth.

In any event, you're correct that anything massive enough or impacting fast enough to significantly heat the core of Mars would surely disarrange the planet to no end.

[super]*[/super]Gravitational Binding Energy for a Planet - For a spherical planet of uniform density:

U = 2GM[super]2[/super] / 5R

G = Gravitational Constant
M - Mass of the spherical body
R = It's radius

I acknowledge your point. I was just attempting to give some sense of scale, without going too deep on details. It's not clear in tejolson's post that he comprehends the size of Phobos is miniscule compared to Mars - NOT a criticism of him, he did ask questions.

But in any event, Martian real estate isn't going to be very useful to us afterwards for a very, very long time....

 

[yevaud]

I acknowledge your point. I was just attempting to give some sense of scale, without going too deep on details. It's not clear in tejolson's post that he comprehends the size of Phobos is miniscule compared to Mars - NOT a criticism of him, he did ask questions.

But in any event, Martian real estate isn't going to be very useful to us afterwards for a very, very long time....

Of course. This was an SDC "Teaching Moment" for his benefit.

And noooo, I kinda think several hundred degrees C within a goodly distance of the impact zone wouldn't help much. Nice and toasty for a while though. Big enough an impactor, and it'd heat a large portion of the surface to a molten or near-molten state.

The best plan I even heard - repeated by various SF authors over the years - is to construct giant Mylar reflectors in orbit and vaporize the poles with the reflected and focused light. Also continually bombard the surface with icy bodies from the belt. Raise the gas pressure nice and high, as well as pumping in a lot of H and O2.

 

[tejolson]

Very informative guys, thank you... So forgot that. How bout we use Apophis to experiment. I wanna see an anti-hydrogen bomb. That's an anti-nuclear explosion, not a nuclear, so it's Kosher right? But would it need anti-gravity to push the hydrogen together? If regular pressure would do that trick, wouldn't that disprove anti-gravity? I think general relativity disproved it quite well to be honest.


How bout instead of an impact we change the dynamics a bit. Add a diamond head to Apophis and do some math. Change it's rotation so it's going at Mars like a dart. I'm thinking if it's off at an angle it will cut into upper crust and it will orbit inside. Trick is to get the orbit right.

Another trip off topic. You think that massive olympus valcano was from tectonic activity? I just figured it was like that one from the moon where a shockwave made it. If these two massive waves combined it would have a really nice wave period. I was also thinking about the 42 minute free fall trip to anywhere on Earth. Does that apply to shock waves thru the crust? Could gravity keep the shock wave at almost full integrity? Could the crust split the wave into two waves?

 

[yevaud]

I wanna see an anti-hydrogen bomb. That's an anti-nuclear explosion, not a nuclear, so it's Kosher right?

An "Anti-Hydrogen" bomb would work identically as a regular matter hydrogen bomb. Er, with the caveat that for us to produce anti-hydrogen in sufficient quantities would take probably all of the power available on the entire planet Earth, we don't know how to contain that much safely, and so why bother?

Or, if you're saying an antimatter bomb using anti-Hydrogen, the above all still applies. IIRC, we've been able to produce and briefly contain something like a tiny fraction of a percent of a picogram of antimatter in all of our total experiments trying to produce it. So, entirely cost-ineffective.

How bout instead of an impact we change the dynamics a bit. Add a diamond head to Apophis and do some math. Change it's rotation so it's going at Mars like a dart. I'm thinking if it's off at an angle it will cut into upper crust and it will orbit inside. Trick is to get the orbit right.

Nope, won't work. Diamond is only relatively hard, but not such that it could remotely stay intact in an impact event. And it wouldn't work anyways.

Another trip off topic. You think that massive olympus valcano was from tectonic activity?

No, because Mars doesn't have any tectonic activity and for that matter, doesn't appear to ever have had such. As I'd said earlier, Olympus Mons is a "hot spot" volcano, like Hawaii - as if you took a red-hot poker and melted a passage through something, not as in here (mostly) along plate boundaries. And Mons has been dead for quite a long time.

 

[SJQ]

An anti-matter bomb has all the problems of a regular thermo-nuclear weapon, plus at least one other. First of all, the fall-out, whether from the bomb itself or the Martian rock it is detonated in, is fall-out - radioactive. Anti-matter doesn't have any magical properties, it's just a way to liberate the energy in (anti)matter a lot (orders of magnitude) more efficiently. Such a bomb would release a lot of energy, but the resultant fracturing of Mars causes us more grief than it's worth.

"At least one other" problem with an anti-matter weapon is providing sufficient anti-matter to build a weapon. Anti-matter isn't lying around - it long ago detonated itself, if indeed it was actually created (actually, just storing anti-matter in a matter world is another problem - it can not touch anything, else bang! whether you're ready or not). One of the issues with the Big Bang theories is "where is the anti-matter?"

We know anti-matter is real - we've made it. In vanishingly small quantities. There is a lot of energy in a chunk of matter, and the same amount in equal masses of anti-matter. Einstein's E = mc[super]2[/super] applies to both. That means that to create anti-matter, you have to supply the necessary energy in some kind of accelerator. I'm not sure what the world's total production of anti-matter to date is (not much - femtograms, if we really got ambitious), but the energy that all of it together could liberate is probably well south of a fly's fart.

Bombs just aren't the way to go - we can't build one big enough to supply the energy needed, and bombs apply the energy the wrong way - too concentrated, and too fast. To melt the core, you want heat, not shock, applied at a rate the rock can actually melt at.


Building a diamond cutter head for Apophis, even if we could, would be a waste of time. The diamond would just fracture (what didn't just vapourize) on the shock of impact (how do you think jewellers rough-shape cut diamonds? Same principle, and effective even on a vastly smaller energy scale).

I'd have to do some digging regarding relative masses/momentums/kinetic energies, but off-hand, substituting one rock (Apophis) for another (Phobos) isn't going to help. Still not enough available energy, and still largely shock energy, with only a side-order of melt on the Martian surface. Plus, Phobos is already handily located in the immediate Martian neighbourhood, and Apophis isn't, so there's a lot of additional energy expenditure just moving a rock to the target's area.

The only way you could possibly get any rock to orbit inside the volume of Mars is dig a cirum-Martian tunnel and evacuate all the air out of it. Given the right velocity (and the occaisonal course correction nudges), your rock could fall forever, but the object of the exercise was to melt the Martian core, not dig holes. I think this tunnelling is your reference to the 42-minute free-fall, but I'm not sure. Given that rock won't orbit through rock, I don't see the point of this idea. If you are looking for tidal heating caused by an orbiting body, sure, a smaller mass closer in will eventually achieve the same effect, all else permitting, but a tunnel-size rock is microscopic, gravitationally. Mars would radiate the tidal heating away as fast as such a small rock could cause it.

Olympus Mons and all of the other major Martian volcanoes are unlikely to be the result of plate tectonics - they are just too big to form near a subduction zone. Their massive size requires time to accumulate, and plate tectonics implies that the fracture zones move around, or seal up (plates can join - India and Asia, as an example). The experts can say better than I, but I don't think Mars ever had plate tectonics, and even if it did, it was certainly not for a long time.

These volcanoes are most probably situated over Martian "hot spots", weak places in the crust where plumes of magma could penetrate and reach the surface. On Earth, Hawaii, the Galapagos Islands, Yellowstone, and several other hot spots are known to exist (still active), even it their creation and behaviour isn't completely understood (what started the underlying plume?). Note that plate tectonics do not prevent hot spots: they just distribute the mass of the resultant volcanoes in chains of mountains - Hawaii, for example, is only the most recent volcano of the chain, and its replacement has already been detected forming under-sea. Hawaii is the biggest mountain on Earth (measured from the sea floor, not sea level), but it is smaller than Olympus Mons. If you added together the masses of all the volcanoes in the Hawaiian chain, then Olympus Mons doesn't do so well. It is bigger than any of the Earth volcanoes because there is no plate tectonics pulling it away from the hot spot. The Hawaiian total is greater because the Earth is bigger (more magma to vent), and the greater mass allows the plume to last longer.

 

[csmyth3025]

All this talk of crashing moons into Mars and/or exploding "anti-hydrogen" bombs there reminds me of Neuvik's signature line:

I don't think I'm alone when I say, "I hope more planets fall under the ruthless domination of Earth!"

Pity those poor little underground Martian critters when we show up!

Chris