The abstract of the interesting 2001 NASA JPL paper Covering a Sphere with Retroreflectors says:

Abstract- One of the future missions for Mars involves returning a soil sample from the Martian surface to Earth. The sample will be deposited in a spherical canister, shot into Mars orbit and then subsequently captured by a spacecraft for the return journey. This paper discusses how retroreflectors can be placed on the orbiting sample canister with the objective of maximizing returned light from a scanning laser system. The retroreflectors are vital for acquisition of the sample canister during the terminal rendezvous phase (< 5 km) of the capture.

Twenty years have passed so the mission design has likely evolved, so I'd like to ask:


  1. Will surface samples from Mars be in a spherical capsule until captured?
  2. Will the samples (no matter the shape of the carrier) be in an actual orbit around Mars, or will the trajectory be sub-orbital?

There are some problems with the optics calculations, no ranging laser is going to have a coherence length of 5 kilometers, so the interference effects between retroreflectors will not cause the nulls and minima they suggest. Yes, as discussed in What is the longest coherence length stimulated-emission beam demonstrated? there are reports of multi-kilometer coherence lengths in fiber lasers, but you have to work extremely hard to make this happen.

This answer to What kind of rocket will ESA(?) launch from Mars? Who will build it? is well-sourced and contains some nice graphics, but there are no details I can see of the sample-containing object that will be captured then flown back to Earth.

enter image description here

Clearly "it's only a model" (longer version)

The NASA-credited images below are from the BBC News article Europe pushes ahead with 'dune buggy' Mars rover and come from the question linked above.

What precautions are planned to prevent samples returned from Mars crashing and releasing organisms on Earth? is a separate but related question.

The Fetch rover will bring the tubes it's collected back to its landing station The tubes will be put in a rocket and fired high above Mars

left: The Fetch rover will bring the tubes it's collected back to its landing station right: The tubes will be put in a rocket and fired high above Mars

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    $\begingroup$ I don't see the question @uhoh, the title doesn't seem to match the body, and there's no actual question in the body. Are you asking if this is the method they plan to use? $\endgroup$
    – GdD
    Jul 27, 2020 at 11:16
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    $\begingroup$ @GdD Thanks! I almost always include a summary/indicator of the actual question, but it seems that I forgot this time. That's probably related to the fact that I'm supposed to be actually doing something right now rather than playing Stack Exchange ;-) I've just added one now, up near the top. $\endgroup$
    – uhoh
    Jul 27, 2020 at 11:22
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    $\begingroup$ Surely you have asking questions down to a science by now @uhoh! $\endgroup$
    – GdD
    Jul 27, 2020 at 11:23
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    $\begingroup$ @GdD yes, the same way I had drinking beer "down to a science" a million years ago and these days drinking coffee; it's simply an addiction. $\endgroup$
    – uhoh
    Jul 27, 2020 at 11:26
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    $\begingroup$ a suborbital capture would be very hard and would need new techniques; orbital rendezvous is well understood. $\endgroup$
    – user20636
    Sep 7, 2020 at 9:58

1 Answer 1


Many sources. (eg this one) mention the samples orbiting Mars in a "basketball-sized" container until collected by the Earth Return Orbiter. I haven't seen any authoritative ones saying it's also shaped like a basketball.


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