Is it a floating sugar cube? A grain of salt under a microscope? No, it’s the asteroid Ryugu! The Japanese Space Agency (JAXA)’s Hayubusa 2 mission made history earlier this month by successfully landing two probes on this space rock that’s only 900 metres in diameter, the first ever probes to be landed on an asteroid. The mission will spend over a year at Ryugu and one of its main aims is to collect samples to bring back to Earth for analysis. If all goes to plan this will be a major achievement in space exploration – to date the Moon is the only solar system body from which mankind has been able to collect and bring back significant amounts of samples.
NASA also has a spacecraft en route to an asteroid, with a similar mission to investigate and bring back samples: OSIRISREx, on course to arrive at 500 metre-diameter asteroid Bennu in December this year.
So why is there so much interest in asteroid exploration, enough to justify not one but two missions to asteroids orbiting between Mars and Earth?
The answers to some very big questions could be at stake. From a purely scientific point of view, asteroids like these two are likely to hold important clues about the origin of the solar system and of life. Both Ruygu and Bennu are believed to be ancient remnants of the original solar system nebula from which the planets formed. Also, they are formed of carbon-based materials, and some of their minerals may well contain water.
Since carbon and water are essential elements for life on Earth, and asteroid fragments are continually falling to Earth as meteorites, these missions aim to find clues about the possible role of space rocks in delivering the ingredients of life to Earth.
Filling stations in space?
From a more practical point of view, asteroid material could be very valuable in itself. The minerals and water that they contain could be mined and used as fuel for spacecraft, and the asteroids’ low gravity would make it much less difficult to lift these materials into space than from a planet.
And if in-space refuelling were to become possible, eliminating the need to continually return to Earth, human exploration of Space and even extra-terrestrial settlement would become much more feasible. Sample collection by Hayubasha 2 and OSIRISREx is a perfect opportunity to test out possible mining technology. This could revolutionise the future of humanity!
The other side of the coin of course is that asteroids present a very real threat to Earth and humanity. A direct collision with an asteroid could, depending on its size, cause immense damage to our civilisation. Asteroid Bennu is considered ‘potentially hazardous’, with a 1 in 2700 risk of collision late in the next century.
So OSIRISREx’s mission is also to improve understanding of Bennu’s trajectory, including the effect on its movements of the sun’s radiation (known as the ‘Yarkovsky Effect’), which will be valuable in developing plans to deflect it if necessary.
But how exactly could Bennu or any other hazardous asteroid be deflected if on a collision course with Earth?
Probably the simplest technique that is considered feasible is a ‘kinetic impactor’ , which just involves smashing a projectile into the asteroid to change its course, and NASA plans to test technique in 2021 with a mission known as ‘Double Asteroid Redirection Technique ‘ or DART. The spacecraft will deliberately crash into a small satellite of asteroid Didymos – this moonlet is only 150 metres across and the impact should change its orbit only fractionally, but enough to be observed telescopically from Earth.
If this demonstration is successful, it should be a major step forward in humanity’s ability to reduce our home’s vulnerability to space rock catastrophe.
http://global.jaxa.jp/projects/sat/hayabusa2/
https://www.asteroidmission.org/ OSIRISREx mission
http://www.planetary.org/blogs/jason-davis/2018/20180620-new-neo-threat.html
https://www.nasa.gov/planetarydefense/dart
https://cneos.jpl.nasa.gov/about/cneos.html Centre for Near Earth Objects Studies
1. JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST
2. NASA
3. NASA