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Space Forum / Space Flight / May 2004Comets to Mars?
In _Entering Space_ Robert Zubrin mentions that it would take only a small amount of Delta V to send Kuiper Belt Objects down to Mars. He believes comets striking Mars would thicken the atmosphere and raise the temperature. (I also seem to recall Kim Stanley Robinson using this idea in his Mars trilogy) But now in John S. Lewis' _Rain of Iron and Ice_ I read about atmospheric erosion by meteorites. Most the atmosphere the other side of a tangent plane touching the Martian sphere at point of impact is sent into space. So would comets add or subtract to Mars' atmosphere? By my calculations KBOs sent on a Hohmann transfer orbit to Mars would come into Mars orbit at about 9 km/sec. Mars gravity would add another 5. So I believe a KBO would hit Mars at around 14 km/sec.  SignatureHop David http://clowder.net/hop/index.html > In _Entering Space_ Robert Zubrin mentions that it would take only a > small amount of Delta V to send Kuiper Belt Objects down to Mars. He [quoted text clipped - 12 lines] > come into Mars orbit at about 9 km/sec. Mars gravity would add another > 5. So I believe a KBO would hit Mars at around 14 km/sec. If the impact is vertical then most of the momentum of the impacting object would be absorbed by the martian crust. If the impact is off vertical then more of the momentum would go into the atmosphere but I suspect would be transferred over the whole trajectory of the object. I doubt that the mass lost from the atmosphere would be anywhere near as much as delivered by the impacting body. ---- Michael Smith Mail address and GPG key available from www.netapps.com.au >>In _Entering Space_ Robert Zubrin mentions that it would take only a >>small amount of Delta V to send Kuiper Belt Objects down to Mars. He [quoted text clipped - 17 lines] > then more of the momentum would go into the atmosphere but I suspect would > be transferred over the whole trajectory of the object. So a hit smack dab in middle leaves more mass than grazing a limb? > I doubt that the mass lost from the atmosphere would be anywhere near as much > as delivered by the impacting body. Is this true regardless of velocity? I guess atmospheric erosion is caused by stoney or metallic meteorites that don't replace ejected atmosphere with gas of their own. If high velocity did cause a net loss maybe pelting Mars with Trojan snowballs would be better than KBOs. > ---- > Michael Smith > Mail address and GPG key available from www.netapps.com.au SignatureHop David http://clowder.net/hop/index.html > By my calculations KBOs sent on a Hohmann transfer orbit to Mars would > come into Mars orbit at about 9 km/sec. Mars gravity would add another > 5. So I believe a KBO would hit Mars at around 14 km/sec. I've wondered what the effect would be of putting pairs of ice bodies into close flyby trajectories either side of Mars, aimed so they collide. Say aim one over the north pole, one over the south and get a big bang over the equator. Hopefully you get a big cloud of steam with insufficient velocity to stay up... Anthony Signature| Weather prediction will never be accurate until we | | kill all the butterflies | > > > By my calculations KBOs sent on a Hohmann transfer orbit to Mars would [quoted text clipped - 8 lines] > > Anthony I'd rather put them into retrograde resp. direct orbit, then scatter them into two opposing accretion discs. Regards Carsten Nielsen Denmark > > > By my calculations KBOs sent on a Hohmann transfer orbit to Mars would [quoted text clipped - 8 lines] > > Anthony Or maybe smack Deimos to bring it down to Mars synchronous and Phobos to bring it to the surface. Those might be first steps to building a Martian bean stalk. If Phobos and Deimos are piles of rubble, the collisions might result in huge clouds of debris that would be a nuisance for some time to come. SignatureHop David http://clowder.net/hop/index.html |But now in John S. Lewis' _Rain of Iron and Ice_ I read about |atmospheric erosion by meteorites. Hmm.. I think I'll check out http://www.amazon.com and see if it is available there. |Most the atmosphere the other side of a tangent plane touching the |Martian sphere at point of impact is sent into space. Is the atmosphere permanently lost, or does it eventually come back down? I'd think that loss of atmosphere is something that is undesirable; does this still happen if the meterorites are broken up (with nuclear bombs, so they become fragmentary or shatter) before they enter Mars' atmosphere? |So would comets add or subtract to Mars' atmosphere? How much mass can you count on coming from those comets that you can locate and drive to the near vicinity of Mars? Don't you lose some of that mass, just driving the comets into Mars's orbit? |By my calculations KBOs sent on a Hohmann transfer orbit to Mars |would come into Mars orbit at about 9 km/sec. Mars gravity would add |another 5. So I believe a KBO would hit Mars at around 14 km/sec. If you don't first break the meteorites up before entry, you are going to get a lot more surface material mixed into the atmosphere, but if you can successfully break them up first, the atmosphere itself is going to be the only thing to slow down the meteorites' entry. >In _Entering Space_ Robert Zubrin mentions that it would take only a >small amount of Delta V to send Kuiper Belt Objects down to Mars. He [quoted text clipped - 8 lines] > >So would comets add or subtract to Mars' atmosphere? Depends on their size and impact velocity. >By my calculations KBOs sent on a Hohmann transfer orbit to Mars would >come into Mars orbit at about 9 km/sec. Mars gravity would add another >5. So I believe a KBO would hit Mars at around 14 km/sec. It would be easy to avoid the atmosphere losses and large-scale areophysical effects resulting from a straight-in impact of a large body by arranging a suitable pre-impact with a much smaller body to disrupt the main incoming body. Such a pre-impact would convert the incoming into an expanding sphere of rapidly declining average density, spreading the impact out over an entire hemisphere and a much longer period of time. Even objects as large as peta-ton class could probably be "soft-landed" on Mars using this technique, avoiding the significant atmosphere losses and awkward long-term areophysical consequences of large straight-in impacts. -- Roy L |
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