Such as this one, which is not necessarily simpler, but still interesting. Back in the 70's some consideration was given to modifying a Viking lander by removing everything but one camera, the sample arm, the S band transmitters and the power supply, then replacing what was removed with a sample return rocket.

This would be carried to Mars by one Viking Orbiter, another Viking Orbiter would carry the Earth Return Stage.

At the appointed time the sample return rocket would be launched, rendezvous with the Earth Return Stage and the contents sent back to Earth for analysis.

It's quite clear from the study (see links below) that all other science was going to be sacrificed in favor of the return of the Martian Soil sample.

See:

1. A Feasibility Study OF Unmanned Rendezvous & Docking in Mars Orbit. Vol 1. Summary (1.9mb)

2. A Feasibility Study OF Unmanned Rendezvous & Docking in Mars Orbit. Vol 2. Technical Studies & Results (17mb)

International Group Plans Strategy For Mars Sample Return Mission

http://www.marsdaily.com/reports/Internati...ission_999.html

Some pretty good news, I would say.

Thanks, Cugel.

I like the extensive international cooperation, but worry about 'requirements wars'. It can be pretty damn difficult to reach a consensus with a large cardinal number of stakeholders from different organizations. Hopefully, the mission definition will be as clear-cut as possible to avoid this mess, 'cause it ain't fun at all, plus such wars tend to really jack up costs...

I think a sample return could be pretty clear cut for international cooperation. Here's one break down that could make sense:

Rover caches:

ESA - ExoMars
USA - Follow on rover to MSL (astrobiology field rover?)
USA - MSL as backup

Lander and ascent craft

Nation n: Cruise, landing stages
Nation n: Rover to get cached samples
Nation n: Ascent vehicle

Retrieval craft

Nation n: Cruise craft to reach Mars and Mars orbital operations
Nation n: Earth return craft to leave Mars orbit and cruise craft
Nation n: Earth entry craft

This breakdown assumes one particular MSR architecture (separate craft to retrieve samples from Mars orbit) but many others are possible. I think the sample return mission makes international cooperation easier than in most missions.

Some 'current events' which indicate an increasing emphasis on MSR:

January 2008: This month's issue of Aerospace America has an article titled "Mars Exploration: Digging Deeper," by Leonard David, contributing writer. MSR is featured prominently. The argument is made that the Mars Program needs to keep doing new and exciting things to justify its 46% share of NASA's planetary budget. More orbiter and rover missions alone might not be enough to maintain excitement and political support. On the other side of that coin is a concern that MSR might displace ongoing Mars efforts to such a large degree that there would be a net detriment to the Mars Program and to Mars science. One interviewed science leader expressed the importance of having MSR become an ongoing program to encompass multiple missions, rather than one win-or-lose flagship mission.

Given all these concerns, a way must be found to make MSR affordable for multiple attempts within the current budget (just over a half billion US dollars per year). However, the article did not delve into the unique technology needs for MSR.

My own comments: Is there anything that affects the mission scale and cost more so than the need to deliver a launch vehicle and its ground support equipment to another planet? Is there a more direct path through the above dilemma than building a miniature launch vehicle (or at least finding out definitively how small one can be)?

February 20-21, 2008: The Mars Exploration Program Analysis Group (MEPAG) is meeting in Southern California. Sample return is on the agenda for this discussion among (mostly) geologists. See http://mepag.jpl.nasa.gov/meeting/feb-08/index.html

April 21-23, 2008: A science meeting in Albequerque is named "Ground Truth from Mars: Science Payoff from a Sample Return Mission." Sponsors include the Lunar and Planetary Institute and NASA. Discussion topics include Mars exploration strategy, sampling strategy, and specific topics in geology and astrobiology. See www.lpi.usra.edu/meetings/msr2008/8

Also in the near future, NASA is planning a MSR Technology Workshop to discuss the following topics:
1. Rendezvous and Sample Capture (in Mars orbit).
2. Earth Entry Vehicle (the part that lands in Utah like Stardust did).
3. Returned Sample Handling Technologies on Earth.
4. Sample Acquisition, Sample Handling, and Encapsulation on Mars (packaging for shipment to Earth).
5. Forward Planetary Protection and Organic Contamination (how to not contaminate Mars with Earth life and related chemistry).
6. Entry, Descent, and Precision Landing (for Mars arrival, improved from prior Mars landers).
7. Back Planetary Protection (how to avoid any possibility that Mars life or molecules could harm life on Earth).
8. Mars Ascent Vehicle.

As far as I can see there are three ways of acquiring martian samples without having to go all the way down into the gravity well and up again, and we have already been over them several times:

1. a Stardust type mission to collect dust from high in the Martian atmosphere

2. a sample return mission to Deimos or, preferably, Phobos. There is almost bound to be martian material there.

3. Go to Antarctica/Arabia etc and search for more martian meteorites (incidentally a project to go around the world's museums, particular the smaller ones, and see what they already have would very likely be successful - museum drawers are frequently the optimum locality to look for things)

[...]

Of course, nothing can compete with a well documented Mars sample returned to Earth, but I would like to say a few good words about Mars meteorites. They provide ground truth for parts of Mars' surface, we just don't know what parts of the surface. But just maybe CRISM or some future hyperspectral imager will be able to correlate some Mars meteorites with specific areas of the Martian surface. It won't be perfect, but Mars meteorites are an extraordinary bargain (cost-wise) that really do tell us a lot about Mars.

I think, maybe it was pointered to from here, that there's a major hi-geo-geek-level book coming out on the geochemistry, igneous petrology, and all the implications of that from the mars rock meteorites for the geology, geophysics and history of mars.

[...]

John - You and I have ended up reaching the same conclusion -- we need several (I say at least 2, better 3; you say 4-5) sites sampled. I think this may be doable with enough partners: one does the rover, one the landing and ascent, one for the orbital retrieval. A couple of nits/questions. I talked with a senior Mars scientist in December who believes that once the MSL candidate sites are fully studied, they'll be lucky to have a choice of two. So there may not be that many sites that are safe to land on with foreseeable landing systems. Second, if we are going to keep the ascent vehicles cheap, how much more mass is needed to launch into a polar orbit versus an equatorial orbit? I think we may have to select from equatorial sites, only, if the mass penalty is too large.

Well, here's another thought -- instead of relying solely on Mars Orbit Rendezvous (MOR) to collect up all of your separately-launched samples, why not add to this with an element of Mars Surface Rendezvous (MSR)?

It seems to me that the most challenging part of this architecture, both to land on Mars and to get back up off of it again, is the ascent vehicle.

If you want to sample six types of terrain, would it make sense to land six ascent vehicles and then go hunt their easter eggs in Mars orbit, using up tremendous amounts of propellants in rendezvous maneuvers? Or would it make *more* sense to land only two ascent vehicles, each of which is loaded with samples from three different rovers? (I'm thinking that it *must* be easier and cheaper to design, build and fly two MAVs which can each place 30 kilos of samples into orbit than it is to fly six such vehicles which can each loft 5 kilos of samples.) Yeah, you'd "bunch up" each set of three rover sites into something like 100-km circles around each MAV (assuming your rovers can drive as far as 50 km to deliver their samples), but that seems a small price to pay. Besides, there must be many locations on Mars where you can access several different and interesting geological units within a 100-km circle.

Granted, you'd be betting that your rovers would be able to navigate to your ascent vehicles. But again, success could be a graded event -- if only one of your ascent vehicles worked, or if only one or two rovers were able to deposit samples in each, you'd still be looking at a pretty successful mission.

And you'd only need enough fuel in your Earth return/orbiter vehicle to make two rendezvous maneuvers, not six. That could be a truly substantial mass savings.

Yes, we're talking about spending something similar to what Apollo cost just to get 50 or 60 kilos of Mars back to Earth -- at least four major Ares V-type launches, probably more, and a *lot* of spacecraft all operating at once cost a lot of money. But it's a fraction of what putting men on Mars will cost, and a lot of people would argue it's scientifically justifiable.

-the other Doug

[...]

Well -- in re rendezvous issues, my thoughts come back to the fact that the U.S. has yet to prove a capability of autonomous rendezvous. A DoD test was attempted a few years ago, and it ran out of fuel before it achieved station-keeping with its target.

I grant you that the Russians have been doing it for years, and the Europeans will be jumping into the fray within the next month. But that's in LEO, where ground tracking data can be instantaneously incorporated into a vehicle's on-board solutions.

I'm also thinking of how rendezvous works. Your sample-carrying pods will have to be the passive targets -- your weight penalties are highest for the vehicles that you actually land on Mars, so the extra prop you need for rendezvous maneuvers will all have to ride in your orbiter. Making multiple rendezvous means you have to adjust the orbiter's orbit for every object you want to meet up with. Unless the sample pods are all in nearly identical orbits, and most importantly are in nearly the same place in those orbits at a given time, you could require from weeks to months of operations trying to reach each one. And if you end up with any significant out-of-plane elements, you exceed the available energy required to rendezvous pretty quickly.

So, for example, if you end up with two sample containers in nearly identical orbits but, say, separated by 120 degrees of orbit arc, you'll need to phase your orbiter back or forward through a third of an orbit, which is pretty energy-intensive.

And remember, you have to loft all of the fuel you need to reach your sample pods all the way from the surface of the Earth into Mars orbit. For every ounce of fuel you deliver to LMO, you have to spend thousands of pounds of propellants just to get it there.

Until and unless we demonstrate an autonomous rendezvous/docking capability in LEO that allows a satellite to travel around to various objects in various orbits, I'm not certain we're talking about sometihng that's within our technical competence at the moment...

-the other Doug

That was DART, a NASA mission. The DOD test, Orbital Express, was very successful last fall