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Are there any plans to launch a sample return mission to Mars?

Is such mission possible, and what would be approximate max weight of returned sample?

Is it possible to return sample to Earth orbit and retrieve it there and save on thermal shielding on return vehicle?

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    $\begingroup$ It is harder to get to earth orbit (Need to decelarate all the way down to orbital speeds) than to reenter, and let the heat shield do the work. $\endgroup$ – geoffc Dec 5 '13 at 18:59
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It is possible and there are several such missions planned or proposed:

  • Russian Roscosmos proposed Mars-Grunt mission that should be based on the Phobos-Grunt sample return technology (the first Phobos-Grunt went sour, but I hear they started planning Phobos-Grunt 2). The sample return weight would be about 0.2 kilograms (0.44 lb) according to this Roscosmos Space Missions (PDF) document.
  • China has plans to explore Mars in a similar fashion as they're now doing with Lunar exploration, so orbiters first, then landers, followed by sample return missions by 2030, and so on. China tends to build two identical craft instead of just one, so that adds quite a bit to mission robustness in case of unexpected failure. The mass and size of the return samples they would target is yet unknown.
  • Joint NASA-ESA plans via Mars Joint Exploration Initiative were targeting 2020-2022 time frame but that's now uncertain due to cancellation of the Mars Astrobiology Explorer-Cacher (MAX-C) concept rover mission. MAX-C project targeted return of 20-sample cache, likely under half a kilogram in weight.
  • NASA has many proposals via its Mars Exploration Program, for example the Mars Next Generation mission with planned sample return in the 2018-2024 timeframe (Summary of the Final Report, Mars Program Planning Group (PDF)), Mars 2020 rover mission that is also a concept under study with target launch date in 2020 with ambitions to return samples, and so on. Mars 2020 rover mission is proposed to collect up to 31 samples of rock cores and soil, each 1 cm in diameter.

And there might be other such planned mission in different project stages. As for possibility to do so, there are many possible ways to go about it, and some such concepts are listed on the Wikipedia on Mars sample return mission - NASA proposals, listing one-launch architecture using Hall effect thruster, two-launches architecture with orbiter and lander with a return stage and I presume Mars Orbit Rendezvous, and three-launches architecture with a sample collecting rover, an orbiter, and a Mars Ascent Vehicle (MAV).

For the last part of your question, if it is possible to capture returned samples in Earth's orbit, I believe that it would be, but likely not needed if you're using two- or even three-launch architecture with a Mars orbiter safely storing returned samples in its body. The sample return capsule also needs not be large and can be built to withstand Earth aerobraking and deploy a parachute once it has sufficiently slowed down its descent on reentry. E.g. sample cache could look something like this:

   enter image description here

   Prototype for hardware to cache samples of cores drilled from Martian rocks for possible future return to Earth (Source: NASA)

So this is not such a big sample cache that would be held in a return capsule, and can hold 31 samples with each core 0.4 inch (1 centimeter) in diameter. Problem is, you'd still need a spacecraft to deliver the sample capsule to Earth and inject it in reentry trajectory that is shallow enough for the capsule not to disintegrate in the atmosphere, and without constant corrections, that would be nigh impossible to do from Martian orbit. Simply hurling samples off Mars and towards the Earth wouldn't work. Miss by a nanometer at your departure and you won't arrive at your destination where you planned to, either by far missing the Earth or hitting it too direct and your capsule will burn on reentry. And that's assuming your calculations were absolutely precise to start with, with no margin of error to speak of, and no trajectory corrections required.

So if you have a powered vehicle with thrusters onboard delivering the capsule, like your Mars orbiter or in one-launch architecture an all-in-one spacecraft, it's simply easier (and cheaper) to just drop it into a ballistic trajectory from near Earth than to change its orbit to rendezvous with another craft or a space station in Earth's orbit. Especially, since you'd need powerful retrorockets and propellants for them, all adding to total weight of your spacecraft, to slow down to a more circular orbit suitable for rendezvous from what would be a highly elliptical orbit on your return to Earth.

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  • $\begingroup$ FYI, the joint NASA-ESA plans are not uncertain. They have been certainly cancelled. $\endgroup$ – Mark Adler Dec 5 '13 at 22:45
  • $\begingroup$ @MarkAdler To my understanding, the MAX-C was canceled but that doesn't exclude any other such future joint missions via Mars Exploration Joint Initiative that was signed in 2009. Last I heard, French (CNES) are pretty active in preparing proposals for sample return missions to Mars, so that'd likely be a joint venture if they can get it past the drawing board of course. $\endgroup$ – TildalWave Dec 5 '13 at 22:51
  • $\begingroup$ It's always possible for future joint US-ESA missions to be planned. However, after the US pulled out after years of planning, I'm not holding my breath. The previous plans were cancelled, except for the US providing a relay radio on the ExoMars orbiter. ESA has now turned to Russia for future cooperation on ExoMars. $\endgroup$ – Mark Adler Dec 5 '13 at 23:23
  • $\begingroup$ @MarkAdler I kept that mention of ESA-NASA there in the list more as a demonstration of what mass, size and number of samples we can expect from any missions like that and to name some such concepts. Now, of course neither of mentioned missions might in reality even make it to launch, that's inherent to early mission planning. ESA might as well cooperate more with China (they already do to some extent with Chang'e 3), Russia is also very likely, and we shouldn't exclude even other options (ESA, Roscosmos and Israel perhaps?). We'll have to wait and see, none are on the launchpad now. ;) $\endgroup$ – TildalWave Dec 5 '13 at 23:43
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There have been plans to return samples from the surface of Mars for about the past 46 years. There was a project initiated in 1998 to return samples by 2008, but it was cancelled in 2000 due to other Mars mission failures in 1999.

Currently the first part of a Mars Sample Return (MSR) mission is in serious planning, which is a sample caching missing to be launched in 2020. It is not an approved mission yet, but it is well on its way. That first step would collect rock cores and other samples and store them in a can, called the cache, on the rover for later retrieval. This is the closest we've gotten to a "real" MSR project since 2000.

The 2020 mission could be followed by another lander, this time with a rocket to launch the samples into Mars orbit. Then a return orbiter could pick up the samples in Mars orbit, bring them to Earth, and send an entry vehicle in with the samples to land. Those missions being further in the future are in much more nascent stages of planning.

Returning samples from Mars, while difficult and complicated, is certainly possible. One thing that has been relatively consistent over the years is that the sample collected and returned would be on the order of 500 grams of material.

One of the requirements on MSR is to not inadvertently release Martian samples into Earth's environment on entry or landing. The samples have to go through an isolated receiving facility on Earth first and be investigated there before they can be released into Earth's environment for more open use in other laboratories. As a result, the safest approach appears to be direct entry and landing, since that can be done with the simplest, most robust vehicle with large margins. It doesn't even need a parachute. Going into Earth orbit, being retrieved by another vehicle, and then safely entering and landing that vehicle adds more failure modes for inadvertent entry and breakup.

The whole point is to get the samples into Earth laboratories, so sooner or later they have to enter and land.

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