Universe Today
Japan’s space agency, JAXA, has been knocking it out of the park with small-body exploration missions for decades. They had historic successes with both Hayabusa and Hayabusa2, and they are going to visit the Martian Moons soon with the Martian Moons eXploration (MMX) mission. But after that, they are aiming for something much more pristine and arguably more difficult - a comet. The Next Generation Small-Body Return (NGSR) was recently described in a paper at the Lunar and Planetary Science Conference (LPSC), and is under assessment as a large-class mission for the 2030s.
Its main target is the comet 289P/Blanpain, a unique comet that has an interesting history. It was originally discovered in 1819, but was then considered “lost” for two centuries, eventually being rediscovered in 2003. Originally it was mis-identified as a near-Earth asteroid due to its relatively low activity, but was confirmed as a comet after it had an unexpected outburst of activity in 2013. It’s extremely small, with an estimated 160 meter radius. But the most important feature is its relatively low rate of gas and dust production - making it a much safer environment for NGSR to perform proximity operations in than an actively erupting larger comet.
But why pick a comet in the first place? Asteroids, such as Ryugu, which Hayabusa2 returned samples from, have been beaten up over billions of years by impacts, solar radiation, and space weathering. Even the surface of comets aren’t perfectly pristine - they’re affected by cyclic solar heating and their own outgassing. But under their surfaces, comets hold potential samples of primordial ice and dust from when the solar system was young.
Fraser discusses NASA’s abandoned Comet Sample Return mission.NGSR intends to excavate and sample those materials. The concept can be broken down into two major goals. First is to understand what kind of stars forged the material that eventually became our Sun and planets. Since asteroids have experienced constant heating and alteration, the “presolar” material within them has been compromised. Comets, on the other hand, spend most of their time far out from the Sun, allowing them to act as miniature deep-frozen time capsules. They’re expected to hold these interstellar materials in the original state, allowing us to get a peek at what the early solar system was really made up of.
Some of the most interesting things we could potentially find are the building blocks of life. We know certain carbonaceous meteorites contain organic matter, including amino acids. If NGSR finds pristine, pre-solar organic materials hidden beneath a comet’s surface, it would provide direct evidence that the chemical precursors for life were delivered from the stars.
The second goal for the mission is centered around planet formation. We don’t currently understand the exact mechanism of how microscopic dust grains managed to overcome the barriers (such as gas drag) to clump together into kilometer-sized “planetesimals”. Since asteroids were originally part of a larger body, the destroyed and re-accumulated over time any evidence of the early structures they were a part of has been erased. NGSR will deploy seismometers and use a bistatic radar to probe the internal structure of the comet, looking for meter-sized voids in its structure that could hold clues as to how planetary formation actually started.
Fraser talks about JAXAs success stories.Currently, the mission is planned for launch in 2034, and will span 14 years from launch to sample return. The spacecraft itself will consist of two main components - a Deep Space Orbital Transfer Vehicle (DSOTV) to handle the cruise phase between the Earth and the comet, and a dedicated lander for actually landing on the comet’s surface.
Once it arrives at 289P/Blanpain in 2041, it will spend 1.5 years performing proximity operations. During that time, it will use its optical navigation camera (ONC), a laser altimeter (LIDAR), and a thermal infrared camera (TIRI) to detect surface properties of the comet. After its initial assessment, the mission will use a Small Carry-on Impactor (SCI) - which was also used on the Hayabusa2 mission - to blast a crater in the comet and expose its pristine subsurface. In other words, the lander will touch down, shoot the comet, and collect the resulting material to send back to Earth.
The actual sample return phase won’t be as easy as Hayabusa2 though. Cometary samples are rich in highly volatile organics that might be lost before the spacecraft makes it all the way back to Earth. So the lander will be equipped with an ultra-small multi-turn time-of-flight mass spectrometer (MULTUM-sp) to analyze them directly in-situ. Even once they are collected, the samples will be freeze dried, loaded onboard a Sample Return Capsule, and sent back to Earth for a landing in 2048, where they will be immediately whisked away to a cryogenic clean room designed specifically to handle the pristine building blocks of the solar system.
If JAXA can pull all this off in the next 12 years, it will only add to its legend as the foremost experts on small-body science in the world. And it will also potentially give us the first true look at what our solar system was truly originally made out of.
Learn More:
N. Sakatani et al. - NEXT GENERATION SMALL-BODY SAMPLE RETURN (NGSR): A CONCEPT STUDY FOR A FUTURE JAPANESE MISSION TO A COMET
UT - Japan's Next Sample-Return Mission Could be to a Comet
UT - We Have the Technology to Retrieve a Sample From an Interstellar Object Like Oumuamua
