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Proposed CAESAR mission could return a sample from comet 67P/Churyumov–Gerasimenko

Artist's rendering of the CAESAR spacecraft acquiring a sample from the comet 67P/Churyumov–Gerasimenko.

Artist’s rendering of the CAESAR spacecraft acquiring a sample from the comet 67P/Churyumov–Gerasimenko. Image Credit: NASA

A proposed mission known as Comet Astrobiology Exploration Sample Return (CAESAR), could greatly improve our knowledge about the origin and history of the comet 67P/Churyumov–Gerasimenko. If selected by NASA, it could return a sample from this comet to Earth, enabling scientists to study the leftover material from the formation of our Solar System.

CAESAR is one of the two finalists for the space agency’s next mission under the New Frontiers program. The project should receive funding through the end of 2018 to further develop and mature the mission concept. The decision whether or not CAESAR is selected for the development and launch will be made by the agency in the spring of 2019.

“We are just beginning Phase A of the mission. The focus of Phase A is developing and defining the project requirements and cost/schedule basis, and designing a plan for implementation,” Steve Squyres of Cornell University in Ithaca, New York and CAESAR’s Principal Investigator, told

In its current configuration, the CAESAR probe is based on Orbital ATK’s GEOStar-3 electric propulsion spacecraft, with a configuration that emulates the arrangement used for NASA’s Dawn mission. Power for the spacecraft will be provided by large Roll-Out Solar Arrays built by Deployable Space Systems.

Comet 67P/Churyumov–Gerasimenko as seen by ESA's Rosetta mission on January 7, 2016.

Comet 67P/Churyumov–Gerasimenko as seen by ESA’s Rosetta mission on January 7, 2016. Image Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

The science payload of CAESAR would be dedicated to sample acquisition and preservation, and consists primarily of a Sample Acquisition System (SAS), a Sample Containment System (SCS), and a Gas Containment System (GCS). The final element of the science payload is a camera suite designed for selecting the sample site and documenting the sampling process.

When at the comet, SAS should acquire the sample and SCS should store the solid sample. When it comes to GCS, it is designed to store volatile materials that evolve from the solid sample. After completing its science mission at 67P/Churyumov–Gerasimenko, the SCS and the GCS components are planned to return to Earth onboard the spacecraft.

“CAESAR is a sample return mission. All aspects of the mission have been designed to maximize the scientific value of the returned sample. So the main CAESAR science will take place in laboratories on Earth, using state-of-the-art instrumentation to analyze both non-volatile and volatile material from comet 67P,” Squyres said.

CAESAR will be the second mission to 67P/Churyumov–Gerasimenko. The first spacecraft sent to this comet was ESA’s Rosetta, which arrived there in August 2014. The mission’s Philae lander has performed the first successful landing on a comet in November of 2014.

In general, Rosetta delivered crucial information, improving our understanding of comets. The results provided by the spacecraft suggest that comets are ancient leftovers of early Solar System’s formation, rather than fragments of collisions between larger bodies later on.

Now, scientists believe that the CAESAR mission, which is seen as Rosetta’s successor, will be even more fruitful when it comes to acquiring essential scientific data.

“Rosetta laid the groundwork for CAESAR by providing detailed remote sensing and in situ investigation of the nucleus of 67P. The information gathered by Rosetta is part of what makes CAESAR possible. CAESAR will make a quantum leap beyond Rosetta by acquiring a sample from the nucleus of 67P and bringing it back for analysis in laboratories on Earth,” Squyres noted.

However, Squyres underlined that the best mission to compare CAESAR to scientifically would be NASA’s Stardust, which returned a sample from the coma of the comet 81P/Wild. The material was collected by flying through 81P’s coma in January of 2004 at more than 13,400 mph (21,565 kilometers). The total sample mass collected by the spacecraft was about 1 milligram, and the samples were significantly modified by heating during the high-speed collection process.

“In contrast, CAESAR will collect about 100 grams of sample, 100,000 times more than Stardust. The CAESAR sample will be collected at ambient comet temperatures, and protected from alteration all the way through the Earth return process. The Stardust mission was a substantial achievement, and provided significant discoveries regarding the nature and origin of comets. CAESAR will be a quantum leap beyond Stardust,” Squyres said.





Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.

Reader Comments

So there’s CAESAR, that revisits a comet we’ve already been to. And we wouldn’t see that sample return until 2038. And then there’s Dragonfly, which puts a flying drone on Titan so we can study the only other lakes in the solar system up close. And Titan may be a better place to colonize than Mars.

Just say no to CAESAR.

James Lunar Miner

Mining comets and mining Titan should offer lots of useful future options.

Titan’s thick atmosphere should provide extensive and effective shielding from space radiation and could eventually make long human surface trips or atmospheric flights quite doable.

Both the CAESAR and Dragonfly missions are needed.


“Dr. Robert Zubrin has pointed out that Titan possesses an abundance of all the elements necessary to support life, saying ‘In certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization.'”

“Colonization of Titan” Wikipedia

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