Stardust mission returned samples of another comet's tail. The Philae lander successfully landed on Comet Churyumov–Gerasimenko in 2014 as part of the broader Rosetta mission. Deep space exploration Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with the exploration of distant regions of outer space. Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft. Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion. The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes. Future of space exploration Breakthrough Starshot Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft named StarChip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away. It was founded in 2016 by Yuri Milner, Stephen Hawking, and Mark Zuckerberg. Asteroids An article in science magazine Nature suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars. In order to make such an approach viable, three requirements need to be fulfilled: first, "a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit"; second, "extending flight duration and distance capability to ever-increasing ranges out to Mars"; and finally, "developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin". Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them without great risk to radiation exposure. James Webb Space Telescope The James Webb Space Telescope (JWST or "Webb") is a space telescope that is the successor to the Hubble Space Telescope. The JWST will provide greatly improved resolution and sensitivity over the Hubble, and will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe, such as the formation of the first galaxies. Other goals include understanding the formation of stars and planets, and direct imaging of exoplanets and novas. The primary mirror of the JWST, the Optical Telescope Element, is composed of 18 hexagonal mirror segments made of