Sample return mission

A sample-return mission is a spacecraft mission with the goal of collecting and returning samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as loose material ('soil') and rocks. These samples may be obtained in a number of ways, such as soil and rock excavation or a collector array used for capturing particles of solar wind or cometary debris. A sample-return mission is a spacecraft mission with the goal of collecting and returning samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as loose material ('soil') and rocks. These samples may be obtained in a number of ways, such as soil and rock excavation or a collector array used for capturing particles of solar wind or cometary debris. To date, samples of Moon rock from Earth's Moon have been collected by robotic and crewed missions, the comet Wild 2 and the asteroid 25143 Itokawa have been visited by a robotic spacecraft which returned samples to Earth, and samples of the solar wind have been returned by the robotic Genesis mission. In addition to sample-return missions, samples from three identified non-terrestrial bodies have been collected by means other than sample-return missions: samples from the Moon in the form of Lunar meteorites, samples from Mars in the form of Martian meteorites, and samples from Vesta in the form of HED meteorites. Samples available on Earth can be analyzed in laboratories, so we can further our understanding and knowledge as part of the discovery and exploration of the Solar System. Until now many important scientific discoveries about the Solar System were made remotely with telescopes, and some Solar System bodies were visited by orbiting or even landing spacecraft with instruments capable of remote sensing or sample analysis. While such an investigation of the Solar System is technically easier than a sample-return mission, the scientific tools available on Earth to study such samples are far more advanced and diverse than those that can go on spacecraft. Analysis of samples on Earth allows to follow up any findings with different tools, including tools that have yet to be developed; in contrast, a spacecraft can carry only a limited set of analytic tools, and these have to be chosen and built long before launch. Samples analyzed on Earth can be matched against findings of remote sensing, for more insight into the processes that formed the Solar System. This was done, for example, with findings by the Dawn spacecraft, which visited the asteroid Vesta from 2011 to 2012 for imaging, and samples from HED meteorites (collected on Earth until then), which were compared to data gathered by Dawn. These meteorites could then be identified as material ejected from the large impact crater Rheasilvia on Vesta. This allowed deducing the composition of crust, mantle and core of Vesta. Similarly some differences in composition of asteroids (and, to a lesser extent, different compositions of comets) can be discerned by imaging alone. However, for a more precise inventory of the material on these different bodies, more samples will be collected and returned in the future, to match their compositions with the data gathered through telescopes and astronomical spectroscopy. One further focus of such investigation—besides the basic composition and geologic history of the various Solar System bodies—is the presence of the building blocks of life on comets, asteroids, Mars or the moons of the gas giants. Several sample-return missions to asteroids and comets are currently in the works. More samples from asteroids and comets will help determine whether life formed in space and was carried to Earth by meteorites. Another question under investigation is whether extraterrestrial life formed on other Solar System bodies like Mars or on the moons of the gas giants, and whether life might even exist there. The result of NASA's last 'Decadal Survey' was to prioritize a Mars sample-return mission, as Mars has a special importance: it is comparatively 'nearby', might have harbored life in the past, and might even continue to sustain life. Jupiter's moon Europa is another important focus in the search for life in the Solar System. However, due to the distance and other constraints, Europa might not be the target of a sample-return mission in the foreseeable future. Planetary protection aims to prevent biological contamination of both the target celestial body and the Earth—in the case of sample-return missions. No sample has yet been returned with alien life in it. A sample-return from Mars or other location with potential to host life, is a category V mission under COSPAR which directs to containment of any unsterilized sample returned to Earth. This is because it is unknown the effects of such hypothetical life would be on humans or on the biosphere of Earth. For this reason, Carl Sagan and Joshua Lederberg argued in the 1970s that we should do sample-return missions classified as category V missions with extreme caution, and later studies by the NRC and ESF agreed. The Apollo program returned over 382 kg (842 lb) of lunar rocks and regolith (including lunar 'soil') to the Lunar Receiving Laboratory in Houston. Today, 75% of the samples are stored at the Lunar Sample Laboratory Facility built in 1979. In July 1969, Apollo 11 achieved the first successful sample return from another Solar System body. It returned approximately 22 kilograms (49 lb) of Lunar surface material. This was followed by 34 kilograms (75 lb) of material from Apollo 12, 42.8 kilograms (94 lb) of material from Apollo 14, 76.7 kilograms (169 lb) of material from Apollo 15, 94.3 kilograms (208 lb) of material from Apollo 16, and 110.4 kilograms (243 lb) of material from Apollo 17. One of the most significant advances in sample-return missions occurred in 1970 when the robotic Soviet mission known as Luna 16 successfully returned 101 grams (3.6 oz) of lunar soil. Likewise, Luna 20 returned 55 grams (1.9 oz) in 1974, and Luna 24 returned 170 grams (6.0 oz) in 1976. Although they recovered far less than the Apollo missions, they did this fully automatically. Apart from these three successes, other attempts under the Luna programme failed. The first two missions were intended to outstrip Apollo 11 and were undertaken shortly before them in June and July 1969: Luna E-8-5 No. 402 failed at start, and Luna 15 crashed on the Moon. Later, other sample-return missions failed: Kosmos 300 and Kosmos 305 in 1969, Luna E-8-5 No. 405 in 1970, Luna E-8-5M No. 412 in 1975 at unsuccessful launches, and Luna 18 in 1971 and Luna 23 in 1974 at unsuccessful landings on the Moon.