Sample Return Missions
As the Solar System was being formed 4.5 billion years ago, fragments of rock and metal orbited the sun, colliding to form large spinning masses that increased in size and gravity to form the terrestrial planets – Mercury, Venus, Earth, and Mars. Much farther away, a safe distance from the scorching heat of the solar winds, the “gas” and “ice” giant planets formed.
The Asteroid Belt, located between the orbits of Mars and Jupiter, and the Kuiper Belt, the expanse beyond the orbit of Neptune, contain remnants from that time. Rather than becoming part of a planet or moon, the asteroids and comets within these regions collided with each other, breaking apart and then settling into a stable orbit.
Asteroids are composed of rock and metals, similar to the composition of the terrestrial planets, while comets contain water-ice and are only found in the outer regions of the Solar System
In recent years, scientists from around the world have been racing to “catch up” with both asteroids and comets in order to study them. They’re interested in their composition, in tracking changes in their trajectory, and discovering whether or not they contain organic compounds that could prove that life on earth might have evolved from organisms found within these interplanetary rocks.
The ESA’s Rosetta spacecraft, with its lander, Philae, connected with comet 67P Churyumov-Gerasimenko in August 2014 after a ten-year journey. Comet 67P travels on a highly elliptical orbit that originates in the Kuiper Belt and intersects the solar system between the orbits of Earth and Mars every 6.45 years. Rosetta mapped the surface of 67P and determined a landing site for Philae. Philae descended to the surface, but its harpoon failed to deploy and the lander bounced twice and then became stuck under a ledge that blocked its solar panels from being recharged. Scientists are studying the data from both Rosetta and Philae for information about the water-ice that 67P is composed of and to identify the organic molecules that were emitted in water vapor as the comet flew near the sun.
In 2007, NASA’s Dawn spacecraft traveled into the Asteroid Belt to study Vesta and Ceres. After a four year journey from Earth, Dawn arrived at Vesta in July of 2011 and spent a year taking detailed photographs of its terrestrial surface. Dawn then continued on and was placed in orbit around the dwarf planet, Ceres, where it studied and imagined its surface, confirming many of NASA’s predictions. In October of 2018, the propellant that was powering the spacecraft was depleted, and Dawn could no longer orient itself to recharge it’s solar panels. It remains in silent orbit around Ceres and NASA scientists have stated that the mission was successfully concluded.
From 2003-2010, JAXA’s Hayabusa (named for the peregrine falcon, the fastest bird on earth) successfully landed on asteroid 25143 Itokawa, collected rock samples, and then returned to earth. When JAXA scientists analyzed the space dust, they theorized that Itokawa was once part of a much larger asteroid but broke apart when it collided with another object about 8 million years ago.
The Hayabusa 2 was launched in December of 2014 and arrived at asteroid 162173 Ryugu on June 27, 2018. JAXA’s latest mission, besides deploying four lander/rovers, includes firing projectiles at the surface of Ryugu to collect rock samples from deep beneath the asteroid’s weathered exterior. The samples will be returned to earth in December 2020.
NASA’s Osiris-REx spacecraft is equipped with sophisticated cameras and spectrometers to analyze the NEO (near earth object) asteroid 10155 Bennu. This asteroid was chosen by NASA for a sample-return mission because of its proximity to earth and its composition. Scientists are hoping to find that Bennu is composed of carbonaceous rock containing amino acids and other organic compounds that might confirm the theory that life on earth began with molecules that exist in other parts of the universe. Osiris-REx was launched in September 2016 and arrived at Bennu in December 2018. The spacecraft will carefully study Bennu for approximately a year. In July of 2020, a sample of surface rocks will be collected and returned to earth in a capsule that will land in the Utah desert in September 2023.