Sample return mission

"Genesis Rock" returned by the Apollo 15 lunar mission

A sample return mission is a spacecraft mission with the goal of returning tangible 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 dirt and rocks. These samples may be obtained in a number of ways, including a collector array used for capturing particles of solar wind or cometary debris, soil and rock excavation, mining, and any other possible way for retrieving samples in the environment.

Sample return missions

Past

The first sample return mission ever was Apollo 11 in 1969. It returned approximately 22 kilograms of Lunar surface material. Apollo 12 was the second sample return mission which returned about 34 kilograms of material. Apollo 11 and Apollo 12 and further missions 14, 15, 16, 17 were manned missions. Perhaps 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 of lunar soil. Likewise, Luna 20 returned 30 grams in 1974 and Luna 24 returned 170.1 grams in 1976. Although they recovered far less than the Apollo missions, they did this fully automatically.

The Soviet Union planned for 1975 (according to plans of 1970) the first Martian sample return mission by Mars 5NM project launched by N1 superrocket that never flew successfully and planned for 1979 but cancelled the further Mars 5M project double-launched by Proton rocket.

The Earth-Orbital Debris Collection (ODC) experiment, deployed on the Mir space station for 18 months during 1996–1997, used aerogel to capture interplanetary dust particles in orbit.

Current

An artist's rendering of Genesis while collecting solar wind

After the last sample return mission by Luna 24 in 1976, more than twenty five years passed before another mission, known as Genesis was able to return an extraterrestrial sample to Earth from beyond Earth orbit. Unfortunately, the Genesis capsule failed to open its parachute while re-entering the Earth's atmosphere, and it crash-landed in the Utah desert in 2004. There were fears of severe contamination or even total mission loss, but scientists have managed to save quite a bit of the samples—which were the first to be collected from beyond lunar orbit. Genesis used a collector array made of wafers of ultra-pure silicon, gold, sapphire, and diamond. Each different wafer was used to collect a different part of the solar wind.

Another sample return mission is NASA's Stardust spacecraft which returned to earth January 15, 2006. It safely passed by Comet Wild 2 and collected dust samples from the comet's coma while imaging the comet's nucleus. Stardust used a collector array made of low-density aerogel (99% of which is empty space) which has about 1/1000 of the density of glass. This permits the ability to collect the cometary particles without damaging them due to high impact velocities. Particle collisions with even slightly porous solid collectors would result in destruction of those particles and damage to the collection apparatus.

In June 2010 the Japan Aerospace Exploration Agency (JAXA) Hayabusa probe returned to Earth after a rendezvous with (and a landing on) S-type asteroid 25143 Itokawa. In November 2010 scientists at the agency confirmed that the probe successfully retrieved dust from the asteroid, the first ever brought back to Earth in pristine condition.

The Russian Fobos-Grunt is a sample return mission to Phobos, one of the moons of Mars. It was launched on November 8, 2011. However the probe failed to leave Earth orbit. It has since crashed into the Pacific Ocean.

Future

An artist's impression of a Mars sample return mission launching its payload back to Earth

China is planning to conduct a Lunar sample return around 2017. If successful, it would make the first lunar sample return in over 40 years.

NASA has long planned a Martian sample return mission, but has yet to successfully design, build, launch, and land a probe that would do just that. There have been mission proposals in the past, but most have not made it far beyond the drawing boards. The mission remains on NASA's roadmap for planetary science as of the 2013 Planetary Science Decadal Survey.

There were plans to launch a Mars Sample Return (MSR) mission in 2004, but following the twin-failures of the Mars Climate Orbiter and Mars Polar Lander, MSR was cancelled. A Mars Sample Return mission with collaboration with Europe (Aurora programme) may launch around 2018.

Russia has Mars-Grunt project for Mars sample return mission near 2020-2023.

Other missions may bring back samples from asteroids and comets.

The OSIRIS-REx mission will be launched in 2016 on a mission to return samples of from asteroid 1999 RQ36. The samples are expected to enable scientists to learn more about the time before the birth of our solar system, initial stages of planet formation, and the source of organic compounds which led to the formation of life.

JAXA's Hayabusa 2 is a sample return mission to C-type asteroid (162173) 1999 JU3. It is planning to launch in 2014 or 2015.

Methods of sample return

Sample return methods include, but are not restricted to the following:

Collector array

A Genesis collector array consisting of a grid of ultra-pure wafers of silicon, gold, sapphire, and diamond

A collector array may be used to collect millions or billions of atoms, molecules, and fine particulates by using a number of wafers made of different elements. The molecular structure of these wafers allows for the collection of various sizes of particles. Collector arrays, such as those flown on Genesis are ultra-pure in order to ensure maximum collection efficiency, durability, and analytical distinguishability.

Collector arrays are useful for collecting tiny, fast-moving atoms such as those expelled by the Sun through solar wind, but can also be used for collection of larger particles such as those found in the coma of a comet. The NASA spacecraft known as Stardust implements this technique. However, due to the high speeds and size of the particles that make up the coma and the area nearby, a dense solid-state collector array was not viable. As a result, another means for collecting samples had to be designed as to preserve the safety of the spacecraft and the samples themselves.

Aerogel

Main article: Aerogel

A particle captured in aerogel

Aerogel is a silicon-based, porous, solid with a sponge-like structure in which 99.8% of its volume is composed of empty space. Aerogel has about 1/1000 of the density of glass. An aerogel was implemented for use with the Stardust spacecraft because the collision of a particle smaller than the size of a grain of sand would have an impact velocity of about six times the speed of a rifle bullet, and hence a collision with a dense solid could alter its chemical composition, and perhaps vaporize it completely.

Since the aerogel is mostly transparent, it is extraordinarily easy for the scientists to find and retrieve the particles since they leave a carrot-shaped path once they penetrate the surface. Since its pores are on the nanometer scale, the particles do not merely pass through the aerogel completely. Instead, they slow to a stop and then are embedded within it.

The Stardust spacecraft has a tennis racket shaped collector with aerogel fitted to it. The collector is retracted into its capsule for safe-storage and delivery back to Earth. One thing that makes aerogel a good choice for missions such as Stardust is that it is quite strong and easily survives both launching and outer space environments.

Excavation and rocket return

Some of the most risky and difficult types of sample return missions are those that require landing on an extraterrestrial body such as an asteroid, moon, or planet. It takes a great deal of time, money, and technical ability in order to even initiate such plans. It is a difficult feat that requires that everything from launch to landing to retrieval and launch back to Earth be planned out with high precision and accuracy.

This type of sample return, although having the most risks, is the most rewarding for planetary science. Furthermore, such missions carry a great deal of public outreach potential, which is an important attribute for space exploration when it comes to publicity.

NASA is considering launching an international sample return mission of this type to Mars around the year 2018, depending on its budget. Previous attempts to launch this type of sample return mission have been scrubbed due to technical difficulty, budget constraints, and other factors such as recent mission failures (e.g.: Mars Climate Orbiter and Mars Polar Lander). The only successful robotic sample return missions of this type have been the former U.S.S.R. Luna landers.

List of unmanned sample return missions

Date launched	Name	Sample	Sample origin	Date recovered	Result
July 13, 1969	Luna 15		The Moon		failure crash-landed on the Moon
September 12, 1970	Luna 16	101 grams (3.6 oz) of lunar rock	The Moon	September 24, 1970	success
September 2, 1971	Luna 18		The Moon		failure crash-landed on the Moon
February 14, 1972	Luna 20	55 grams (1.9 oz) of lunar rock	The Moon	February 25, 1972	success
November 2, 1974	Luna 23		The Moon		failure drilling device damaged on Moon landing, mission abandoned
August 9, 1976	Luna 24	170 grams (6.0 oz) of lunar rock	The Moon	August 22, 1976	success
February 7, 1999	Stardust	over 1 million comet particles	81P/Wild	January 15, 2006	success
August 8, 2001	Genesis	Solar particles	Solar wind	September 8, 2004	partial success parachute failure led to return capsule crash and heavy damage some usable samples recovered
May 9, 2003	Hayabusa	1,500 grains of asteroid particles	25143 Itokawa	June 13, 2010	partial success several hundred milligrams of sample material were planned
November 8, 2011	Fobos-Grunt	200 grams (7.1 oz) of Phobos soil	Phobos	August 2014 (planned)	mission failure
2016 (planned)	OSIRIS-REx	Asteroid regolith	1999 RQ36	2023 (planned)	TBD

See also

• Moon rock for manned sample return missions

External links

• Mars Exploration: Sample Returns Jet Propulsion Laboratory Mars Exploration Program on sample return missions.
• Stardust Homepage Jet Propulsion Laboratory Stardust mission website.
• Genesis Mission Homepage Jet Propulsion Laboratory Genesis mission website.
• Stardust: Aerogel Stardust website on aerogel technology.
• JAXA Hayabusa JAXA Hayabusa project update.
• MarsNews.com: Mars Sample Return MarsNews.com on Mars Sample Return missions.
• Texas Space Grant Consortium: Missions to the Moon A list of missions to the Moon from 1958 to 1998.
• Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies The National Academies, Space Science Board 1998