Our continuing interest in Titan as a possible venue for life was energized last year with the publication of a paper by Martin Rahm and Jonathan Lunine, working with colleagues David Usher and David Shalloway (all at Cornell University). Iâ€™ve written about this one before (see Prebiotic Chemistry on Titan?) and wonâ€™t revisit the details, but the gist is that hydrogen cyanide produced in Titanâ€™s atmosphere can condense into aerosols that are transformed into interesting polymers on the surface. Of these, the most intriguing seems to be polyimine.
The authors see polyimine as capable of producing complex, ordered structures that absorb light, producing energy that can be used to catalyze prebiotic chemistry. Rather than looking in Titanâ€™s seas, the authors think weâ€™ll find hydrogen cyanide reactions in tidal pools on the shores near seas and lakes. Itâ€™s an interesting proposition, and like so many notions about Titan, it requires us to get a payload back to the surface, as we did in 2005 with Huygens. But this time, weâ€™ll want to have extended survivability on Titan and a full suite of instruments.
Image: This composite was produced from images returned on 14 January 2005, by ESAâ€™s Huygens probe during its successful descent to land on Titan. It shows the boundary between the lighter-coloured uplifted terrain, marked with what appear to be drainage channels, and darker lower areas. These images were taken from an altitude of about 8 kilometres with a resolution of about 20 metres per pixel. Credits: ESA/NASA/JPL/University of Arizona.
Thus the news that Dragonfly has won approval as a finalist concept for a robotic launch to Titan in the mid-2020s is encouraging. Dragonfly offers not just a useful instrument package but mobility on the surface in the form of a rotorcraft that could explore numerous sites on the moon. We have to be creative indeed in imagining life that would exist at -180 degrees Celsius in an environment that gets a tenth of one percent of the sunlight Earthâ€™s surface receives. But as Rahm, Lunine and colleagues have reminded us, mechanisms may exist to make it happen.
Elizabeth Turtle (JHU/APL) is lead investigator on Dragonfly, with APL providing project management. The concept involves an eight-bladed drone — two rotors at each of its four corners — capable of sampling widely. Dragonfly would be able to look at prebiotic chemistry of the kind Rahm and Lunine have studied, selecting sites with varying geology and surface composition.
Another key issue for the lander: Is there exchange of organics between the surface and Titanâ€™s interior ocean? Using a Multi-mission Radioisotope Thermoelectric Generator (MMRTG) for power, Dragonfly should be capable of remaining operational not just for months but for years in answering these questions.
Image: Dragonfly is a dual-quadcopter lander that would take advantage of the environment on Titan to fly to multiple locations, some hundreds of kilometers apart, to sample materials and determine surface composition to investigate Titan’s organic chemistry and habitability, monitor atmospheric and surface conditions, image landforms to investigate geological processes, and perform seismic studies. Credit: NASA.
NASAâ€™s competitive peer review process whittled a dozen proposals submitted under the New Frontiers program announcement of opportunity down to a final two, the other being a Comet Astrobiology Exploration Sample Return (CAESAR). Here weâ€™re talking about a return to 67P/Churyumov-Gerasimenko, following up the European Space Agencyâ€™s highly successful Rosetta mission. Both CAESAR and Dragonfly will receive funding through the end of 2018. One of the concepts will be selected the following year for subsequent mission phases.
Expect more on CAESAR in an upcoming article. The Rahm et al. paper mentioned above is â€śPolymorphism and electronic structure of polyimine and its potential significance for prebiotic chemistry on Titan,â€ť published online by Proceedings of the National Academy of Sciences 4 July 2016 (full text). Matt Williams interviews Elizabeth Turtle about Dragonfly in a fine Universe Today article from May of this year.