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Mars Space Science

Russia Planning Double Mission to Mars 239

Posted by Zonk from the anywhere-is-better-than-here dept.
dylanduck writes "Apparently Russia has revived a previous plan to send a spacecraft to Phobos, a tiny Martian moon. Turns out it's a cool place to land - much easier than the surface as far less deceleration is needed, it should have plenty of Mars rocks spattered on the surface and it's just 9000km above the surface. Some think it the perfect place for a Mars moonbase." From the article: "A mission devoted to the moons could explain how the satellites are held together - whether they are piles of rubble loosely held together by gravity or solid chunks. Most scientists assume the heavily cratered moons are captured asteroids, Christensen told New Scientist. But it is actually quite hard for a planet to capture an object into its orbit - most things just skim by. 'So how it got there is a bit of an enigma,' Christensen says."
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Russia Planning Double Mission to Mars More

Russia Planning Double Mission to Mars

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  • Late Breaking News: (Score:5, Funny)

    by TripMaster Monkey ( 862126 ) * on Friday June 24, 2005 @12:50PM (#12902623)

    Once more, panic swept across our fair world when it was revealed by the Council that the invaders from the evil blue planet intend to assault our innermost fortress satellite.
    The fortress satellites, which have stood guard over our world since the Council placed them into orbit over ninety Great Cycles ago, have easily fought off all invaders in the past. Against the cunning machines manufactured by the disgusting water bags inhabiting the evil blue planet, however, the fortress satellites may be more vulnerable than previously thought.

    K'Breel, Speaker for the Council, stressed that there was no cause for alarm:

    "Once again, the evil blue planet seeks to make filthy war against us. They think that by invading and neutralizing one of our fortress satellites, they will secure some measure of victory. Let me assure you, that is far from the truth. The Great Council placed the two fortress satellites in orbit over ninety Great Cycles ago, and have we not advanced since then? Today, at our present level of development, we could easily field two eights-of-eights that number. I know I speak for the Council when I laugh at the pathetic scrabblings of the evil blue planet!"

    When asked if rumours were true that the faction of blue-planet-inhabitants responsible for the threatened invasion was the same as the one who had just recently failed utterly to launch a primitive solar sail device into space, K'Breel laughed maniacally.
  • ...people should really pay more attention to Robert Zubrin [wikipedia.org]. If you haven't read his book, I suggest you do so. He has shown that it is possible to get a mission to the actual planet (not the moons) relatively safely using the same kind of technology that we used to get to the moon in the 1960s. (Of course, with what we have now, it would be "easier" and safer", and those are in quotes merely because I am appreciative of the difficult and danger.)

    We (as humans, not just as specific country-people) need to recapture our pioneering spirit, and get someone to Mars. What we'll learn and accomplish will far outweigh the danger. Imagine if people had been too initimidated to round the horn of Africa, cross the Atlantic ocean, or go to moon! It's time we got that adventurous spirit back, and applied it planet-wide. If we pay attention to our smart people (ie, Zubrin), it's not something that need be far off in the future!

    • Just as long as we don't attempt to create a transporter once we're there...
    • In fact, I would think the planet is a safer place to be than the moons. The moons would have no atmosphere to speak of and are therefore completely exposed to cosmic rays and meteorites that make space so dangerous. Plus, the vacuum requires greater relative internal pressure in the ship or base station. On the Martian surface, even though the atmosphere is not breathable, at least there's some pressure there.

      Although, I suppose you'd want an underground facility on Mars because of those nasty sandstor

      • Re:With all this talk of going to Mars... (Score:5, Funny)

        by Verteiron ( 224042 ) * on Friday June 24, 2005 @01:17PM (#12902948) Homepage
        a decent internet connection will keep the travelers from feeling too cut off

        Except for that pesky lightspeed delay.

        PING earth.ssnet (3ffe:ffff:100:f101::1) 56(84) bytes of data.
        64 bytes from earth.ssnet (3ffe:ffff:100:f101::1): icmp_seq=1 ttl=52 time=14412874.9 ms
        64 bytes from earth.ssnet (3ffe:ffff:100:f101::1): icmp_seq=2 ttl=52 time=14412872.3 ms
        64 bytes from earth.ssnet (3ffe:ffff:100:f101::1): icmp_seq=3 ttl=52 time=14412876.2 ms
        64 bytes from earth.ssnet (3ffe:ffff:100:f101::1): icmp_seq=4 ttl=52 time=14412874.3 ms
      • The great advantage of the moon is that it's a lot easier to get home if something goes wrong. You'll only need a delta-v of about 3 km/s to put you into earth orbit, at which point you can aerobrake or dock with a space station or something. From the martian surface you'd need (pulling a number out of my ass) maybe 10km/s, making your evacuation module much bigger and so heavier to take to mars.
        • Here's a chart. [caltech.edu] The surface of the moon to LEO is 5.5 km/s (and visa versa). Transfer between LEO and Moon orbit is 3.9 km/s. Transfer from LEO to Mars Orbit is 4.7 km/s. Transfer from LEO to Mars Surface is 10.2 km/s (and, again, visa versa).

          Sooo... the lunar surface is about 1/2 of the cost of going to Mars. However, to go to the surface of Mars' moon Deimos, you only need 5.6 km/s! How weird is that?
      • Remember that the U.S. only got its space act together because of perceived Soviet superiority and the fear they would dominate space militarily. Now, probably, China and the E.U. will provide the competition that pushes the U.S. back into space in the next couple of decades.

        For what? I know the reasons why a return to space would probably beneficial and you know them, but the people sitting in Congress would have to have a damn good reason for allocating funds to this (and, quite frankly, the current def

      • Re:With all this talk of going to Mars... (Score:4, Informative)

        by Rei ( 128717 ) on Friday June 24, 2005 @01:55PM (#12903392) Homepage
        I would agree about the planet being better than being on the moon: less radiation, more mineral diverse, more to study, etc. I especially agree with the necessity of cheap launch technology. However, I have trouble putting too much faith in Zubrin, however, as the GP does. Zubrin acts as if all of the problems have been solved (or are almost solved), when they distinctly have not been.

        Lightweight low-power off-planet refining equipment has been "just on the horizon" for decades. So have moderately powerful off-planet nuclear reactors (some very weak ones have been used in Soviet satellites, and RTGs abound, of course). New spacecraft design almost usually runs overschedule and overbudget. Mars eats probes (the "galactic ghoul"), and most of the failures couldn't have been prevented by humans being present. We're just starting to learn the properties of martian dust (if you'll recall, before Spirit and Opportunity experienced natural dust cleaning, it was expected that their panels would have caked over with dust long ago), which poses numerous potential hazards. I have yet to see a satisfying solution from any reputable source for dealing with bremsstrahlung radiation from galactic cosmic radiation (GCR) in transit (I've seen a lot of papers that determine that we can shield safely if we conviently ignore Bremsstrahlung ;) If you have one that covers it, please send me a link). These are just a couple issues for starters; lets not even get into how off-the-wall Zubrin's prices for "long-term colonization" transit to Mars are...

        Yes, we'll make it to Mars. But we're hardly "almost there", as Zubrin, and especially his devout followers, portray.

        P.S. - Minor nitpicks:

        A) Mars has dust storms, not sandstorms. Sand is large particles, dust is fine particles. Dust doesn't usually erode and then leave, but instead electrostatically clings; it's a different set of engineering problems.

        B) Mars's pressure is close enough to being a vaccuum: 0.007 atmospheres on average. It's really only useful for aerobraking, concentration with pumps (for refining, pressurizing things when you're on the surface, etc), and a couple other uses; you'll still have to be in bulky full pressure suits, have fully pressurized dwellings, etc.
        • You haven't read his book. There are issues that are not addressed therein, and a few which are glossed over. However, all of the points you addressed are directly addressed in the book.

          Lightweight low-power off-planet refining equipment has been "just on the horizon" for decades

          Really? Please site. I would love to read about them.

          Fact is there has never been a serious effort to build one, let along plans to actually need it. Americans can engineer anything, once we decide to do it. And automatic minin

          • Re:With all this talk of going to Mars... (Score:5, Informative)

            by Rei ( 128717 ) on Friday June 24, 2005 @06:15PM (#12905617) Homepage
            Oh, great, another time consuming argument with a Zubrin fanboy.

            You haven't read his book

            Outright wrong. Unlike you, I wouldn't be caught dead debating material I haven't read about.

            Really? Please site.

            The word is "cite". A "site" is a location. Here is your "cite" [nasa.gov]: Goal #4 of the Apollo program was to "develop man's capability to work in the lunar environment.". Here's a Lunar Colony [nasa.gov] from 1969. Complete with a smelter. The concept of extracting resources from the moon continued with numerous R&D processes in the late 60s and early 70s; ton-quantities of regolith simulant were produced for the experiments. There was renewed interest in the 1980s with Reagan's call for lunar colonies by 2005.

            Mining under most proposals was to be done simply on regolith, using a three drum slasher [nasa.gov]. Cutler and Krag proposed and investigated a carbothermal oxygen production plant that processed ilmenite desposits. Another 1985 study investigating an entire proposed colony ("Selenopolis"), was to produce 500,000 tons of oxygen per year.

            And automatic mining equipment really isn't that complex.

            That's bloody hilarious. *Manned* mining equipment produced where weight is no object (here on earth) is quite complex. Have you ever seen the work that goes into setting up, for example, a tunnel boring [nasa.gov] system? Mining equipment costs millions of dollars per piece, and it's not for no good reason. Add to that the ridiculous weight, the oxygen-requiring temperature-sensitive engines, etc, and you're stuck paying brand new R&D costs without the benefit of bulk sales and having to use things like lithium-aluminum to cut mass.

            Also, Zubrin et al created a scale model of some of the oxygen mining gear. Worked great, needs to be tested.

            We don't even know specifically where water ice is, yet! (we have some ideas). By the way, have you seen how well electryolysis devices [space.com] as such perform in hostile environments, even with extensive testing and two decades of development? The US has nothing like it [jamesoberg.com] qualified for long term missions - Elektron is the best thing out there (we have some heavy short-term devices).

            Loss of a critical component, and that's the end on Mars. No "repairs" being sent up on "the next flight", no massive backups to "tide you over" (this refers not only to oxygen, but to everything critical for life).

            Apples to oranges comparison. And 100% WRONG. I honestly can't think of ONE of the missions which it could be claimed with any certainty would NOT have been saved without a human around to check things out.

            That's because you've never read about the subject. I hate having to replace a textbook for people like you.

            Mars 1960A: Failed to reach earth orbit due to catastrophic vehicle launch failure. Nothing humans could have done.

            Mars 1960B: Same

            Mars 1962A: Broke into pieces after being launched; pieces remained in Earth orbit for a few days. The equivalent of having more dead humans.

            Mars 1: Communication lost in transit for unknown reasons. Depending on the cause, humans may or may not have been able to salvage it.

            Mars 1962B: Made it to earth orbit. Rocket fire for transfer orbit destroyed the craft. Humans would have perished.

            Mariner 3: Protective shield from earth launch failed to detach. The extra weight prevented it from reaching Mars. As most manned Mars missions don't allow for EVA due to the difficulty and extra mass, at the

            • Re:With all this talk of going to Mars... (Score:4, Informative)

              by Rei ( 128717 ) on Friday June 24, 2005 @06:33PM (#12905766) Homepage
              Correction: SpaceX, not SpaceDev. :) Big difference.

              Also, I forgot to mention one spacecraft that survived that probably would have killed any human cargo on it: Mars Global Surveyor. It had been designed to aerobrake at Mars with its solar panels. However, a joint partly gave way during the maneuver, and threatened to destroy the craft. So, they gave it a much gentler aerobraking approach that made it take many months longer than normal to circularize its orbit - the only realistic solution if they didn't want to tear the craft to shreds. Not a big deal for an unmanned spacecraft; it went on to produce a treasure trove of information over the years. However, for humans, a several month delay means, at best, a failed mission.
      • But with a cheap launch technology, it's the individuals who will truly explore space. Once we're out of Earth's gravity well, private explorers could pretty much go anywhere provided they stocked enough food. Solar cells will provide unlimited energy, and a solar sail the unlimited propulsion. Advanced recycling equipment will minimize the loss of water and other necessities, and a decent internet connection will keep the travelers from feeling too cut off.

        Many of those problems have already been solved
    • Slightly offtopic, but not too far considering the Russian's work in this area. The other day I was poking around to provide some references for the M2P2 technology when I ran across this little beauty. [wikipedia.org] This electric thruster makes Ion engines look downright primitive. According to the various articles, this engine would provide a specific impluse as high as 11,000 (one of the most efficient designs ever created!), but with a relatively high thrust ratio. According to NASA's webpage [nasa.gov], they have been testing a workbench model at powers of up to 30 Mw (!), and they believe that such engines could be used for both deep space missions to Mars, as well as providing more efficient second stage engines for ground launched vehicles.

      Apparently the Russians have done significant work on this area, and continues to perform experiements on behalf of JPL. It's quite possible that the development of this engine could have an even greater effect on space travel than the Ion engine did!

      The only downside to this engine is that it will be likely to require a nuclear reactor for power. This increases weight and adds the danger of a nuclear reactor. The upshot to this is that it is inherently safer than the Orion or NERVA engines, doesn't polute, and can go to Mars and back several times on the same tank of lithium! (Delta-V from LEO to Mars Orbit is about 3900 m/s. Do your own calcs [strout.net] on what that means for an engine with an ISP of 11,000 and a craft that is a mere 25% gas tank.)

      Once again, I'm amazed at the technology already in our posession, or close to being so. Now more than ever, I really feel that we're on the cusp of a true space age.
    • the problem is, at one time we considered it worth life and limb, anymore if someone gets scratched we cry a river.
    • I have read two of his books, and interestingly, I did not see a single mention of Russia.

    • With all this talk of going to Mar people should really pay more attention to Robert Zubrin. If you haven't read his book, I suggest you do so. He has shown that it is possible to get a mission to the actual planet (not the moons) relatively safely using the same kind of technology that we used to get to the moon in the 1960s.

      Umm... No. Zubrin has a very bad habit of treating technologies that are still mostly paper as if they were well tested and proven and quite ready to deploy into the field. I ca

  • I hope they pack well (Score:5, Funny)

    by aldeng ( 804728 ) on Friday June 24, 2005 @12:51PM (#12902635)
    If they forget the shotgun they'll be screwed on like the fourth lebvel.
  • Let me know if the lander encounters any Leather Goddesses of Phobos. (Great '80s game, btw.)
    • > Let me know if the lander encounters any Leather Goddesses of Phobos. (Great '80s game, btw.)

      > SLASHDOT

      Slashdotter descriptions. (Lewd mode wasn't enough for you, was it, you perv?)

      > KISS MY KNEECAPS

      She blushes a bit, and admonishes you with her finger. "Nyet, comrade. In Soviet Russia, kneecaps kiss you!"

  • ...they find a black monolith at the core of the moon. ;P (Yeah, I know... wrong planet and all, but "enigma" and "black monolith" go together so well.)

  • Marsian Moonbase? (Score:5, Insightful)

    by agent dero ( 680753 ) on Friday June 24, 2005 @12:54PM (#12902671) Homepage
    Some think it the perfect place for a Mars moonbase.

    Let's not get ahead of ourselves here, besides the "shock and awe" of getting to the moon, why isn't there a drive for the practicality of a base on our own moon?

    I think it's time that more of our space exploration gets practical, and not HR fodder. "Hey we're technologically superior! We got to mars!"

    How about "Hey, we're technologically superior! We have colonized space and use those colonies as jumping points for marsian missions!"

    Too hopeful? ;)
    • "why isn't there a drive for the practicality of a base on our own moon? "

      I think it is because of all the problems we had with moon base alpha back in 1999.

    • Re:Marsian Moonbase? (Score:3, Interesting)

      by bc90021 ( 43730 ) *
      Read Zubrin's book. There's nothing on the moon. It costs more to land on the moon and then have to get off again, because even though there is less gravity, you still need to break to get to the moon, and then more propellant to get back off. Once you're off Earth, there's no sense in re-encountering gravity when you can go straight to Mars without having to land and take off again.

      Seriously, for everyone who thinks this, go read the book, and you'll learn to stop parroting the "let's go to the moon fi

  • They forgot the New Scientist story link (Score:2, Informative)

    by Anonymous Coward
    The story in New Scientist is here [newscientistspace.com]

  • They'll need a base on each moon to begin the UCP
    teleportation experiments... ... and open the gates to hell...
  • The Russians are going to Mars? At least, they shouldn't have any problems converting measurements [mit.edu].

  • Comment removed (Score:5, Informative)

    by account_deleted ( 4530225 ) on Friday June 24, 2005 @12:57PM (#12902713)
    Comment removed based on user account deletion
    • You know Russians are a very shoe-string type people, a story goes that Americans spent 2 years and a Million dollors to invent a pen that would work in micro-gravity... Russians used pencils. I would not be surprised if Russians make it there first, anyone smell another space race on the way?
    • Wow, you could replace "Russian" with "American" in the parent and it would still be true.

  • Hope/Plan (Score:5, Funny)

    by pete-classic ( 75983 ) <hutnick@gmail.com> on Friday June 24, 2005 @12:59PM (#12902729) Homepage Journal
    I think we have to hope for leather godesses, but plan for daemons.

    -Peter
    • Perhaps we can reassign some of the Marines who get a little too rough with our "guests" at Gitmo to duty on Phobos. Lets hope they don't find that interdimensional gateway, but make sure they are well-armed with plasma rifles and a few BFG-9000s, and plenty of ammo.
  • I, for one, welcome our new pink overlords
  • Some think it the perfect place for a Mars moonbase."

    Don't they remember what happened the last time [wikipedia.org] we put a base on Phobos?

  • Mystery (Score:5, Funny)

    by ndansmith ( 582590 ) on Friday June 24, 2005 @01:02PM (#12902784)
    Most scientists assume the heavily cratered moons are captured asteroids, Christensen told New Scientist. But it is actually quite hard for a planet to capture an object into its orbit - most things just skim by. 'So how it got there is a bit of an enigma.

    Maybe God put it there.

  • How are they going to pay for it (Score:5, Interesting)

    by jockm ( 233372 ) on Friday June 24, 2005 @01:03PM (#12902797) Homepage
    I am all for increasing space exploration, and by all means the more people (or countries) at the party the better, but has there been any coverage of how they plan to pay for this effort?

    They had serious problems meeting their obligations for the ISS, they operated MIR on a shoestring, the economy is improving but do they have the cash for it?

    I hope they do. I hope the US shakes more money loose from the trees for our own programs as well.
    • I am all for increasing space exploration, and by all means the more people (or countries) at the party the better, but has there been any coverage of how they plan to pay for this effort?

      They had serious problems meeting their obligations for the ISS, they operated MIR on a shoestring, the economy is improving but do they have the cash for it?

      I hope they do. I hope the US shakes more money loose from the trees for our own programs as well.

      All you have to do is convince the people that terrorists are no
  • This is just another example of the political rhetoric we hear on a daily basis. They say they're going to go to Mars, but it won't happen. Just like Bush said the US would go to the moon and Mars. It won't happen. This is just a case of politicians being politicians, and spewing out promises that will never be acted upon. Give this a few hours and we'll have forgotten about it.

  • Dusty surface (Score:5, Informative)

    by RobertB-DC ( 622190 ) * on Friday June 24, 2005 @01:06PM (#12902832) Homepage Journal
    Putting a lander on Phobos should be interesting, since the moonlet is covered by a meter-thick layer of dust [arizona.edu]. When I imagine a craft making a landing, I picture throwing a rock into a bowl of flour. On the plus side, maybe we'll make the first sizable, intentional man-made crater outside the Earth.

    I guess Phobos is better then Deimos... the latter is thought to have a layer of dust several hundred feet thick [stardate.org] (or should that be "several dozen meters thick"?
    • Back then, we had as much knowledge of earth's moon, as we do of these moons. And all the naysayers were positive that we would be landing on dust several hundred feet thick and the landers would just sink in. hence the reason for the big feet on them (snow shoes).
  • Don't forget the duct tape. Seems that the russian space agency are doom players.

  • Link properly! (Score:3, Funny)

    by CrazyWingman ( 683127 ) on Friday June 24, 2005 @01:11PM (#12902879) Journal
    Dammit, why doesn't anyone have a proper sense of humor anymore? Clearly the link should have looked like this: Mars moonbase [idsoftware.com].
  • ... much easier than the surface as far less deceleration is needed ...

    I would hope that they would still decelerate all the way before landing. Messy otherwise. Or maybe Phobos has enough velocity relative to Mars that you just sort of slow down a little and hop on?

    (Presumably, the intended meaning was that far less fuel is required for deceleration.)

  • Small moons harder to land on (Score:5, Insightful)

    by JJ ( 29711 ) on Friday June 24, 2005 @01:14PM (#12902918) Homepage Journal
    The two moons of Mars are not very big and although their gravitation is minimal, they don't present very big targets either. In order to land on one, you have to match the speed almost perfectly, then slightly chnage yours and then just as you get there match it again, hopefully you can then latch on.

    While that may not sound like much, for a probe with no help from Earth (Mars is on average 8 light, hence radio minutes away) this is a difficult task.

  • Is there an engineer in the house (Score:3, Insightful)

    by srmalloy ( 263556 ) on Friday June 24, 2005 @01:17PM (#12902949) Homepage
    Turns out it's a cool place to land - much easier than the surface as far less deceleration is needed, it should have plenty of Mars rocks spattered on the surface and it's just 9000km above the surface.

    "Less deceleration" only in that Phobos' gravity well doesn't add much velocity to the probe's velocity as it approaches the moon; however, being airless, it will be impossible to use any aerobraking (unless the mission profile uses a 'skip' into Mars' atmosphere to bleed off excess velocity); having to carry fuel to perform all the deceleration by thrust makes the probe heavier, which increases the amount of fuel required (lather, rinse, and repeat).

  • Right idea, wrong target (Score:3, Insightful)

    by amightywind ( 691887 ) on Friday June 24, 2005 @01:23PM (#12903014) Journal

    Sending a mission to Phobos is like bypassing New York City in order to visit Newark. Phobos is of vanishingly small scientific significance compared to Mars. For some inexplicable reason the Russians are fixated on it. No harm I guess. Wouldn't it make more sense to visit an asteroid of a type not yet encountered (metallic).

  • Mars rocks on the surface (Score:3, Interesting)

    by apankrat ( 314147 ) on Friday June 24, 2005 @01:28PM (#12903066) Homepage
    .. it should have plenty of Mars rocks spattered on the surface

    Funny that they mentioned it...

    Can anyone explain how can 'a plenty of rocks' leave Mars and land on its moon ?

    Bonus question is to explain the appearance of 'martian meteorits' on Earth.

    Somehow I have troubles imagining the level of volcanic activity required to catapult rocks to the neighbouring planets ...
    • The rocks are thrown into space by the impact of meteors. This is how they can hit Phobos or Earth.

      If you've ever looked at the Moon through a telescope (recommended, it's beautiful!), you'll see huge lines of material converging on the craters, this is called "ejecta" and it's the debris thrown out from impacts. Some of the lines cross decent fractions of the Moon's surface, so it's pretty easy to imagine that some of the rock made it all the way out of orbit, and that the same process can operate almost
    • Volcanism just ain't gonna cut it.
      It goes like this:

      Planet
      +
      good-sized asteriod impacting at speed
      =
      lots of ejecta with enough velocity to escape mars gravity and land on small moons and other planets.

      Of course, most of the good-sized asteroids already smacked into planets eons ago, so the odds of it happening in your lifetime are pretty slim.

    • Think of the last good eruption on earth. How high was the dust cloud.

      Why wait to capture an asteroid? Just move Deimos or Phobos over to an earth orbit (I'm still pratting on about my previous post about building a space elevator. It needs an anchor point in orbit. One of those would do it. Then we move the equipment do Mars and repeat the process there. An earth space elevator would be great if it had a mars elevator at the other end.)

      And think of the penal colony potential.)

  • Better hurry up... (Score:5, Funny)

    by amstrad ( 60839 ) on Friday June 24, 2005 @01:28PM (#12903072)
    Phobos' orbit is decaying and will likely crash into Mars or split into a ring within 50 million years [nineplanets.org]
  • At least that's what the text skimming adbot on the rightside of the page for Deimos, Phobos sister moon has. For Phobos you have to be satisfied with ads for relativity and photons and such.
  • You don't need much deceleration to get into orbit around bodies with atmospheres. You just do a small burn to turn your orbit from a hyperbola into an ellipse with a periapsis in the atmosphere and an apoapsis well within the body's hill sphere. Atmospheric drag gives you all the deceleration you need.

    From that point of view, I'd expect Mars would be easier to reach than Phobos, though clearly the latter has the upper hand when it comes to the return trip.

  • I've heard that theory before, but I was always under the impression that the 'accepted version' inolved that pesky asteroid strike which created Olympos Mons and the MASSIVE crater on the opposite side of the planet.

    I suppose small chunks of the same rock could have come in moments later and had some nice happy aerobraking..

    It is a fun problem: once you touch air, you are done without thrusters. There are no mechanisims which raise periapsis (generic term for perigee) fast enough to counter any significa
  • From TFA: "A mission devoted to the moons could explain how the satellites are held together - whether they are piles of rubble loosely held together by gravity or solid chunks. Most scientists assume the heavily cratered moons are captured asteroids, Christensen told New Scientist. But it is actually quite hard for a planet to capture an object into its orbit - most things just skim by. 'So how it got there is a bit of an enigma,' Christensen says."

    Question: Where did our moon come from? What are the non

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