Document 6535954

Sample Return Roadmap Mike Zolensky and Paul Weissman 1. Science a. Superior science of sample return Samples are an eternal resource, as long as they are carefully curated and archived. sample return from asteroids previously studied by remote observa@ons and in-­‐situ/rendezvous measurements can bridge between the ground observa@ons of minor bodies and laboratory analyses of meteori@c samples. In short, there is a mul@plying effect. b. Stardust and Hayabusa as examples Stardust: Major discoveries of Stardust include presence of chondrules and CAI in a comet, which require am more dynamic early solar system than many had envisaged, and verifies predic@ons made by models requiring outward flow of early solar system solids). Carbonates and unusual sulfides were found which poten@ally require ac@vity of liquid water within the comet The bulk mineralogy of Wild 2 grains does not match the mineralogy inferred from Spitzer Telescope spectra of Temple 1 dust. Cometary amino acids have been detected which highlights the cri@cal importance of further developing techniques for organic analysis in small samples, and cleaning outbound spacecraQ. Hayabusa: From the sample return from the Hayabusa Mission, asteroid Itokawa was verified to be a LL5 chondrite, permiVng the first firm link between remotely obtained reflectance spectra of a small body and actual mineralogy Space weathering of an asteroid regolith was characterized for the first @me, and this reveals significant difference between weathering processes and @mescales between asteroids and the Moon Hayabusa seems to have demonstrated that it may be hard for any landed spacecraQ to not collect a sample, since the sample return from Hayabusa was en@rely accidentally collected material. 2. Comet Sample Return a. Surface sample return We do not understand well how to anchor to a comet nucleus, or successfully sample it. The Deep Impact and Stardust NEXT Missions were not completely successful in revealing the nature of a cometary surface, and subsurface, and future missions will face the same uncertain@es regarding comet surface proper@es, and planning for surface opera@ons will con@nue to be difficult. b. Sub-­‐surface sample return Missions that have as a priority the collec@on of cometary vola@les, whether ices, organics of other phases, will probably have to sample the subsurface. mission will require maintenance of the samples at sub-­‐freezing temperatures throughout all aspects of the mission, and all aspects of spacecraQ recovery and sample cura@on and handling. Hard ques@ons include: (1) how deep to sample to guarantee obtaining an “unheated” sample; (2) What should the target temperature for sample maintenance be –40°C?, 0°C?, 150K?, 110K?; (3) How do you keep the sample cool during collec@on; (4) While passive cooling may be adequate during the spacecraQ cruise phase back to Earth, how do you keep it cold during reentry, and how do you ensure that the sample return capsule is located and secured in a @mely manner?; (5) If the sample is accidentally heated during the earth return how do you maintain a separa@on between non-­‐vola@le material and the now gaseous vola@les? 2. Comet Sample Return (cont.) c. How to make the Target selection?
d. Breadth versus Depth – Why and when would you revisit a target?
e. When to visit- High versus low activity?
Big versus small nuclei- Does size matter?
g. Where to sample?
Face it, mission managers may never permit a landing on anything other than a very flat surface.
h. How many sample sites?
Although it may appear obvious that multiple sampling sites should be a mission goal for any sampling
mission, it is not clear that this should always be a mission requirement. It will probably always be the
case that the scientists’ desire for multiple sampling sites will be opposed by Agency (NASA, ESA, etc.)
managers and engineers who desire to minimize mission risks. 3. Asteroid Sample Return a. Justifications, or Why do we need asteroid samples when we already have tens
of thousands of meteorites?
(1) Meteorites are a very biased sampling of small bodies,
(2). We still need to forge links between ground-based spectra to meteorites and to
asteroids, although Hayabusa is a good start).
b. How do we select targets?
(1) Based upon Taxonomic type?
(2) Based upon potential threat?
NEO sample return
(3) Based upon dynamical/Solar System History Criteria?
Main belt asteroid
Trojans and beyond
(4) Based upon searches for water or organics
Volatile rich asteroids (main belt comets)
(5) How driven by quarantine concerns? 3. Asteroid Sample Return (cont.) c. Sampling depth? How deep to get below space weathered surface. Would a few cm be sufficient? If amorphous water ice is a target, does sampling have to be deeper than 1 m? Many m? Would a disaggregated sample be adequate, or would a core sample preserving poten@al stra@fica@on be required? d. Sample site selec;on Within the probable engineering safety concern that will probably mandate a flat sampling surface, i.e. a ponded deposit or similar feature, will it be possible to select a sample site that has some geological advantage? e. How many sample sites? Again, it will probably always be the case that the scien@sts’ desire for mul@ple sampling sites will be opposed by Agency (NASA, ESA, etc.) managers and engineers who desire to minimize mission risks. 4. Dust Sample Return (presumably from generally unknown Comets and Asteroids) a. Stratospheric dust collec;ons NASA ER-­‐2 and WB57F aircraQ with special s@cky collectors capture this dust as it falls through the stratosphere The majority of stratospheric collec@ons are made at random @mes. However, ever since Dermoj and Liou (1994) proposed that there should be enhancements in certain types of asteroidal dust at certain @mes of the year, NASA has endeavored to build up a collec@on of collec@on surfaces targeted at different @mes throughout the year. Eos and Themis family asteroids comet 55P/Tempel-­‐Tujle Comet 26P/Grigg-­‐Skjellerup. b. Space-­‐Exposure Materials Genesis and Stardust sample return capsules and pieces of Surveyor III, the Long Dura@on Exposure Facility (LDEF), the Solar Maximum satellite, the European Recoverable Carrier (EuReCa), and the Skylab, MIR and ISS space sta@ons. 5. Laboratory Analysis Over the 40 years that have passed since the first Apollo samples reached Earth from the Moon, there has been steady progress in instruments for the laboratory analysis of astromaterials. It is beyond the scope of this roadmap to chart the requirements of all analy@cal sub-­‐disciplines. Based upon recent experience with nanogram-­‐sized cometary coma and asteroid regolith grains, we will highlight one area that s@ll requires significant resources and effort-­‐ analyses for organics. a. Organic Analysis One of the scien@fic goals of the Stardust comet and Hayabusa asteroid sample return missions was to establish whether the collected dust contained complex organic materials, and if so, to establish the abundance, chemical, and isotopic nature of the organic phase(s) However, it is very clear that neither the Stardust Mission sampling of Wild 2 nor the Hayabusa Mission sampling of asteroid Itokawa were par@cularly slanted towards organics, since the Wild 2 samples were collected at 6.2 km/hour and Itokawa is an LL5 chondrite asteroid. This it remains for future missions, hopefully beginning with Hayabusa 2, Osiris-­‐REX and Marco Polo, to make more thorough surveys of organics on comets and primi@ve asteroids. 6. Cura;on Facili;es Samples, tools, containers, and contamina@on witness materials for future missions will carry unique requirements for acquisi@on and cura@on. Some of these requirements must represent significant advances over past methods. The Hayabusa Mission Cura@on Lab in Sagamihara, Japan, represents the current cura@on state-­‐of-­‐the-­‐art. a. Atmospheric The Apollo 11 and 12 missions, some of the soil samples were collected in specially designed, sealed Gas Analysis Sample Containers. This work sets a standard for future collec@on of atmospheric gases and vola@les from Mars and the interiors of comets. 6. Cura;on Facili;es (cont.) b. Ices and temperature-­‐sensi;ve minerals Future sample return missions will encounter ices or temperature-­‐sensi@ve minerals. Cura@ng frozen samples introduces significant challenges. The appropriate storage temperature and environment must be selected and maintained. Condensa@on of water vapor and contaminants on the samples must be minimized and monitored. Rou@ne curatorial procedures such as sawing, spliVng, microtomy, and sieving must be modified to prevent the sample temperature from rising. Shipping procedures that maintain the samples both cold and clean must be developed and cer@fied. There is some astromaterials experience at −35◦C We have almost zero experience with the s@ll colder temperatures required for a comet nucleus sample. 6. Cura;on Facili;es (cont.) c. Organic compounds, biohazards, and planetary protec;on The Apollo experience provides a star@ng point for improved quaran@ne and screening of future samples from small bodies with biological poten@al. Recent studies of Stardust Mission samples and Mar@an meteorites have focused ajen@on on the level of organic cleanliness inherent in Cura@on laboratories. Every spacecraQ des@ned for such a mission should be extensively cleaned and contamina@on witness materials collected and preserved, in order to minimize and document possible biological contamina@on of the returned samples. 6. Cura;on Facili;es (cont.) • 
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d. Cura;on Lessons Learned (1) The main point of any sample return mission is laboratory analysis. Everything must be designed, built, and operated to get the highest quality samples to the best laboratories in a @mely manner. (2) Cura@on starts with mission design. Samples will never be cleaner than the tools and container used to collect, transport, and store them. (3) Be ready for con@ngencies. Really bad things happen, but also unexpected good things. Careful planning and well-­‐trained, well-­‐rested people can make a huge difference. (4) Samples collected years or decades ago will yield new discoveries that totally change our understanding of solar system history, as long as samples are properly cared for. (5) More than two full years are required to prepare cura@on facili@es for sample receipt (6) The sample data-­‐base must be fully implemented before sample return, and analysis teams must not be permijed to devise their own sample naming schemes (7) Remote storage of a sample subset is cri@cal. 7. Technology Requirements a. Sample collec;on technique development Sampling techniques that have been considered include drilling, scooping, brush-­‐wheels, and s@cky tape. All of these ideas have problems. How do you collect a subsurface sample without warming it, contamina@ng it, or improperly disaggrega@ng it? b. Autonomous touch-­‐and-­‐go versus landing This technique was tried with Hayabusa, with mixed results. c. Propulsion Chemical, SEP, NEP d. Sample Return Capsule We badly need samples returned in a truly (herme@cally?) sealed container. e. Thermal control of the sample Cura@on of a frozen sample, at any temperature, would require en@rely new facili@es, procedures and skills, none of which currently exist in the planetary science community. 8. Sample Recovery Site: Currently UTTR vs. Woomera Mission Science and Cura@on teams must ac@vely par@cipate in planning, tes@ng and implemen@ng spacecraQ recovery opera@ons. Recovery opera@ons for all recovered sample collec@on spacecraQ significantly suffered from the lack of a herme@c seal for the samples, probably in many addi@onal ways which will only become apparent in the future. Mission engineers should be pushed to true seals for returned samples. 9. Contamina;on Concerns (1) Efforts need to be made both for contamina(on control, i.e., to minimize contamina@on, and contamina(on assessment. (2) Contamina@on control and assessment requires coopera@ve efforts be made that involve the spacecraQ manufacturers, the spacecraQ operators, the mission’s Science Team, and the NASA Curatorial Office. (3) One important issue that everybody on a mission needs to address early is to agree on what is meant by the word “clean” and how this defini@on will translate into opera@onal ac@vi@es (4) During construc@on of the spacecraQ and sampling system, it is cri@cal to document what components/materials are used. Also, never assume that just because the manufacturer promises that a spacecraQ will not significantly outgas, that it won’t significantly outgas (5) It is important to use “witness coupons” to track the introduc@on of contaminates during the manufacture, flight, and recovery of the spacecraQ, and during the subsequent removal of the samples from the SRC. These coupons must to be removed and examined quickly and then archived 10. Preliminary Examina;on (PET, some;mes PE) of Samples There must be some determina@on of the state and quan@ty of the returned samples, to provide a necessary guide to samples requesters and the inevitable oversight commijee tasked with sample cura@on oversight. . Sample PET has never been organized the same way twice. 11. Par;cipa;on in Missions With Interna;onal Par;cipa;on Lessons learned: (1) Pay very close ajen@on in mee@ngs. (2) If at all possible sta@on a US representa@ve at the foreign lead facility-­‐ somebody who is an expert in the foreign language and culture. (3) Make a special effort to form personal rela@onships with the foreign team members. This step is especially cri@cal in Japan. (4) Be very clear about what you are sta@ng, and don’t make commitments you cannot keep. (5) Avoid the Prima Dona factor, and be very careful what you say to the foreign press.