The original sin here really goes back (at least) to when Perseverance was in the planning stages and the caching was added. That decision raised my eyebrows, not as an obvious mistake but as a weird malleability in the planning process, putting tactics before strategy. From at least that point forward, there's been this weird blend between two or more possible future plans, and the consequences of that are what we're seeing now.

Remember that M2020 started out as MAX-C, for which the whole point was caching, it wasn't "added."

But caching goes much farther back, there was a serious proposal to add caching to MSL. See https://www.researchgate.net/publication/22...aching_missions from 2010 for example.

Caching on M2020 always seemed to me like a fairly transparent ploy to get a foot in the door by collecting samples, which would then motivate their return via (in part) the sunk-cost fallacy. (Someone less cynical would just view it as a sensible partitioning of an incremental approach.)

An important aspect, however, is that the caching method allows finding the most scientifically interesting samples to be gathered, rather than whatever is in range of a fixed lander's scoop or robotic arm. China's sample return will just rely on chance to gather whatever happens to be at the landing site. If an interesting rock is a just few cm out of reach, it has to stay there. There's always a tradeoff.

In hindsight, perhaps a much lighter 'Pathfinder' MAV, which just gathered whatever soil/rock was in reach (and perhaps atmosphere samples), would have been a good test of the most critical failure point. But, of course, predicting budgets so far ahead of time is impossible.

This very thread presents an interesting sample of the discussion going back to 2006; it suddenly jumps at one point from 2009 to 2015 in the space of only two posts. I guess the pivotal decision was putting (1) the caching and (2) the return into concrete enough of a plan where the knowledge of whether or not the sampling rover would be usable for the retrieval was unknown. That was not part of anyone's original plan and seems like a sort of operational blackmail a la the sunk cost fallacy.

Reading between the lines of the Washington Post article (or any other coverage) there are people rightly pointing out that risk is inevitable and now someone at the top saying that the things one might trade off to mitigate risk are intolerable. So something has to give. Whether it's a risky but lucky success, years of thumb-twiddling, or Perseverance's samples lost in space remains to be seen.

This is such a big story it even made the Australian mainstream news this morning.

But my question is this - why is this causing such a stink, when almost no-one is talking
about the continuing lack of ice giant orbiter missions that would complete our initial survey
of all the major planets (and probably at less cost and technical risk).

I'm not trying to be smart, I'm truly confused. Someone help me. Is it just because, well
you know, its Mars? Is it the possible life thing? Is it programmatic inertia?

P

Presumably a lot can be learned, yadda yadda.

But yeah, it's Mars, it's the next big obvious thing to do, and NASA et al should do it first after the two big rovers.

I do sort of feel for whomever was calling for innovative mission designs with proven technologies, though.

Mars Sample Return is a huge budget item that has seen its funding rise and fall, which puts a block on other priorities, so that alone makes it news, while a possible mission that has never gotten authorization is almost by definition not news (or very minor news).

An outer planet orbiter will also take years to produce any results in the best case, and I don't think the public imagination would see it as a potential ground-shaker until and unless it found something surprising.

If you polled people on the street, I doubt that many know that missions are on the way to the Mercury, Venus (planned), and jovian systems. But Mars Sample Return would definitely occupy some news cycles, even before the first pebble got under a microscope.

https://spacenews.com/practical-approach-ma...return-mission/

Worth a read, but I'm skeptical of Zubrin's 50-kg total mass Earth return vehicle. And even if the delta V numbers work out in the abstract, he presupposes all the planetary protection requirements can be made to go away.

Interesting and unexpected bogeyman that he identifies and eliminates. Agreed that it is probably not going to be so simple to just wish that requirement away.

I wonder if – if – that is such a large part of the cost, if it could be reduced by moving the point of defense from Mars to Earth: Allow a no-planetary-protection return capsule to leave Mars, come to Earth orbit, and then get protected while in Earth orbit. That still sounds expensive and Rube Goldberg-ish, but would seem to be sub-billions.

Zubrin loves to cut the Gordian Knot. But this particular knot is there for a reason.

No, I don't think this helps. Getting into Earth orbit is either risky (aerocapture) or very expensive in terms of delta V. Unless there is some exotic propulsion system or some complex chaotic trajectory. And once you had it in Earth orbit, then what?

His ISRU solution handwaves the difficulty and complexity of making and storing the propellant, but at least it has slightly better mass margins.

The entire motivation of the MSR program is the study of samples on Earth, anyway. Instruments in Earth orbit are only a slight improvement from those we bring to the surface of Mars.
Part of the issue is that the entry capsule has no parachute, so there's more chance of a breach when impacting at terminal velocity. But the parachute was removed due to mass requirements, as I recall, so adding it back would be counterproductive.
And the only way to decisively remove PP requirements would be to prove a negative, which is essentially impossible (and this forum has rule 1.3 anyway).

My notion was that the protection could occur in Earth orbit, then the protected samples could be brought to the ground. Eg, put the dirty capsule into a casing, the outside of which never touches any martian stuff. Then land.

As mcaplinger notes, this has more than one problem of its own, one of which is risk.

Cassini led to protests because Cassini had plutonium onboard. It's hard to put a price tag or perform rational analysis of risk factors in the public consciousness. But when the cost of the program is $11 billion and a risk factor in the public consciousness is part of that cost, possible cost savings involve manipulating the consciousness of risk, which is not the same thing as risk itself. Zubrin seems to wish the whole thing away. With Cassini, NASA weathered the protests. Note that one of the vocal Cassini protesters was Michio Kaku, who is one of the most prominent publicizers of science and technology.

http://www.cnn.com/TECH/9710/04/cassini/

Planetary protection doesn't have any definite equations governing the risks that it is trying to address. It seems to be a PR exercise with engineering components.

Semi-serious proposals have been made for Earth-orbiting labs to quarantine and examine returned samples. https://www.hou.usra.edu/meetings/deepspace2018/pdf/3189.pdf is a recent example that references the early-80s Antaeus Report https://ntrs.nasa.gov/citations/19820012351

This concept sort of showed up in the (unwatchable IMHO) movie LIFE ( https://en.wikipedia.org/wiki/Life_(2017_film) )

Of course, these would all be staggeringly expensive.

I suspect Zubrin is right and planetary protection from Mars is probably not needed. But it's one of those low-probability/high-consequence things that few people would be willing to risk if it was up to them. And Michael Crichton just did too darn good a job when he wrote https://en.wikipedia.org/wiki/The_Andromeda_Strain

Very helpful links, thanks! And Crichton is the inevitable reference.

Japan proposes the return of some Phobos samples (probably) before MSR. This seems to raise and dispel similar risks since the research expects martian material to exist without the same strong filters as such martian meteorites as make it to Earth. Where there is no equation is in where on the continuum we need to worry and where we don't.

Martian meteorites (already here)
Martian material in Phobos samples
Martian material in the Perseverance tubes (no protection)
Martian material in the Perseverance tubes (some protection)
Martian material in the Perseverance tubes (the most imaginable protection – still breachable by some level of mishap)

Nuclear reactor safety has included such considerations as what would happen if an airplane accident happened to breach the containment. That sounds like an unreasonable level of concern, and yet it has been exceeded on at least two occasions.

I would have said that Phobos sample return was clearly "Category V unrestricted" and thus nothing special had to be done, but apparently there is some question about that, at least according to https://nap.nationalacademies.org/catalog/2...e-martian-moons -- though they ultimately agreed with the unrestricted categorization.

Boeing is offering this strategy: One (bigger) launch from Earth instead of two.

https://arstechnica.com/space/2024/05/nasa-...pensive-rocket/

Massive 'propulsive lander' with MAV that goes direct to earth.

Skycrane is efficient, mars orbit rendezvous is efficient. Idea is drop the efficiencies and use a big rocket?

Can't help but think... Starship booster does 50% more mass than SLS.

It will, when it becomes operational, assuming it meets its original performance goals.

I don't find the Boeing proposal very credible for a whole lot of reasons, but SLS has at least already flown.