Wouldn't Jupiter mess up the plan ?

[Beanze]

I've read countless topics about Mars and how to rejuvenate it, colonize it and all that. One of the suggested methods are pulling a comet or any other huge object and smack it into Mars to start it's core, to revive the magnetic field. Yeah, we would need something to pull the object out of it's current orbit. Hypothetically, when we do this - wouldn't Jupiter's gravitational pull take over once we get too close? Which craft would be capable of disturbing the path a comet currently follows? Do we have such a thing already? I'm guessing it's got to be quite huge, and quite fast.

OT: How do you ... lack of word here... steer an hypothetical future spaceship? I can't imagine depending on trajectories and gravity pulls for all eternity. I assume we would need a whole lot engines/thrusters placed all over the ship. I'm a sad little curious thing aren't i. :roll:

 

[3488]

It would take vastly more than just whacking a comet into Mars to restart it's core. Really that is in the realms of Science Fiction as is terraforming.

Mars is far too different from Earth physically, approx half the dameter, mass only 11% that of the Earth. Internally the two are very different, Earth is a five layered planet (Inner & Outer Cores, Lower & Upper Mantles & Crust), Mars is triple layered, (Core, Mantle & Crust).

Atmosphere is as dense at the martian mean level as Earth's is some 35 KM above sea level. AVERAGE global temperature is minus 63 Celsius, though in places can reach plus 20 C for brief periods in the lower latitudes in the afternoon. Night time temperatures over the whole planet plummet well below freezing.

Perhaps in the far future, some conditions may be tamed, but Mars, is still Mars, the moment human involvement ceases, Mars will certainly begin to revert.

Science Fiction can raise hopes & trigger ideas that may & sometimes work, but regarding Mars, I think it has raised very false unrealistic hopes.

Andrew Brown.

 

[Sycamorefan]

The only way Mars or Venus would ever be habitable for any length of time is to collide them together at the same angle that created the Earth. This would create 1 planet with appx. 1g of gravity and a moon appx. of 0.1-0.2g (sound familiar) The perfect spot to do this would be an orbit just inside where Mars is currently. Now, just got to figure out how to manipulate gravity and not collilide one or both of them with the Earth :lol:

 

[Astro_Robert]

I think if someone wanted to crash somthing into a planet and somehow had the wherewithal to actually do it (very far future for us) then presumably they could take into account all likely gravitational perturbations from the planets and if necessary use Jupiter to help aim the comet. As far as howmuch that would help Mars (increasing its mass by some miniscule amount), I will not venture a guess.

In the meantime, I actually read this one science fiction story, (The Collapsium by Wil McCarthy and apparently there is now at least 1 sequel I shall have to read), about a future where we learned how to clone ourselves (ptich for the book) and make extra dense matter, and to densify existing matter such as the moon. If somehow we could take existing bodies and incease their density and thus surface gravity they would be more able to retain atmospheres. OK so maybe no global magnetic fields, but breathing is a start.

 

[neilsox]

I agree, we need to account for the gravity of Jupiter when hitting Mars with comets. Even a Mars mass imp actor would likely not do much to the core of either planet, so no way is known to start the magnetic field. If we have access to enough energy to send large comets to Mars (possibly useful for other reasons) we can likely use super conductors to give Mars and Venus artificial magnetic fields of adequate strength to reduce ionizing radiation and loss of atmosphere. I also agree, it may never be practical to even partially terraform Mars or Venus, but never is a long time, so maybe. It is however educational to speculate on how it might be done. Neil

 

[eburacum45]

If terraformed, Mars would retain an Earth-like atmosphere for many tens of millions of years; perhaps half a billion according to some estimates. Even if the lower estimates are correct the volatiles on that planet could always be replenished with material from the outer solar system. Just how long do we plan to live there?

The Earth itself will be uninhabitable in half a billion years. If the Earth is still inhabited by life-forms that require an Earth-like environment at that date it will be necessary to re-terraform our own world. If we also have to periodically re-terraform Mars and Venus then that will be no different to re-terraforming the Earth.

 

[Space_pioneer]

Why don't you just heat the atomsphere up enough so it starts releasing the massive amounts of Carbon dioxide in the regolith. Once that starts, the pressure should reach around 300 millibars[Need confirmation?] and we can take off our pressure suits, albeit it will toxic to us, the Northern Basin will flood, and we can start planting lots of plants. With so much Carbon dioxide, would the plants not thrive, if kept under good soil conditions?

 

[neilsox]

Planet size space mirrors would be needed to warm the regloth to 100 c = 212 f, which might slowly release 300 milibars of carbon dioxide and other vapors and gases. The northern, or southern basin, might flood with water. Opinion vary. Since the interior of Mars is likely cooler than Earth''s interior, water might sink all the way to the core, thus requiring a billion cubic kilometers of water to have water lakes on the surface. Most modern plants also need oxygen, so the plant choice is limited, until we have about 200 milibars of oxygen, which might take 100,000 years of photosythesis. 30 degrees c = 86 f would allow vigorous growth of some plants, if water and fertilizer is applied = irrigation. Since the humidity is likely still low, evaporation losses would be high, unless sealed from the rest of the atmosphere. 30 c would only release, perhaps, 100 milibars of carbon dioxide which would likely be better for most plants than 300 milibars. Perhaps genetically modified humans can tolerate 100 milibars with just a face mask for about one hour at a time. Neil

 

[orionrider]

IIRC core activity comes from the molecular compression during proto-planetary aggregation. The cooling process can be slowed or stopped by tidal forces, internal radioactive decay or very large impacts.
However, once the core is cold, the only way to 'reactivate' it would be to move the whole planet close enough to Jupiter.
Not very practical.

And to respond to the OP:

At the moment no human has ever left Earth's orbit and it's not going to happen before 2035 at the earliest (if Obama gets reelected, otherwise it will likely be much later).

Playing with comets and terraforming planets is clearly not on the agenda.