What do coal, crude oil, and truffles have in common? Go ahead. We’ll wait.
The answer is thiophenes, a molecule that behaves a lot like benzene. Crude oil, coal, and truffles all contain thiophenes. So do a few other substances. MSL Curiosity found thiophenes on Mars, and though that doesn’t conclusively prove that Mars once hosted life, its discovery is an important milestone for the rover. Especially since truffles are alive, and oil and coal used to be, sort of.
Titan is a distant, exotic, and dangerous world. It’s frigid temperatures and hydrocarbon chemistry is like nothing else in the Solar System. Now that NASA is heading there, some researchers are getting a jump on the mission by recreating Titan’s chemistry in jars.
In late 1970s and early 80s, scientists got their first detailed look at Saturn’s largest moon Titan. Thanks to the Pioneer 11 probe, which was then followed by the Voyager 1 and 2 missions, the people of Earth were treated to images and readings of this mysterious moon. What these revealed was a cold satellite that nevertheless had a dense, nitrogen-rich atmosphere.
Essentially, Dragonfly would be a New Frontiers-class mission that would use a dual-quadcopter setup to get around. This would enable vertical-takeoff and landing (VTOL), ensuring that the vehicle would be capable of exploring Titan’s atmosphere and conducting science on the surface. And of course, it would also investigate Titan’s methane lakes to see what kind of chemistry is taking place within them.
The goal of all this would be to shed light on Titan’s mysterious environment, which not only has a methane cycle similar to Earth’s own water cycle, but is rich in prebiotic and organic chemistry. In short, Titan is an “ocean world” of our Solar System – along with Jupiter’s moons Europa and Ganymede, and Saturn’s moon of Enceladus – that could contain all the ingredients necessary for life.
What’s more, previous studies have shown that the moon is covered in rich deposits of organic material that are undergoing chemical processes, ones that might be similar to those that took place on Earth billions of years ago. Because of this, scientists have come to view Titan as a sort of planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied.
As Elizabeth Turtle, a planetary scientist at JHUAPL and the principal investigator for the Dragonfly mission, told Universe Today via email:
“Titan offers abundant complex organics on the surface of a water-ice-dominated ocean world, making it an ideal destination to study prebiotic chemistry and to document the habitability of an extraterrestrial environment. Because Titan’s atmosphere obscures the surface at many wavelengths, we have limited information about the materials that make up the surface and how they’re processed. By making detailed surface composition measurements in multiple locations, Dragonfly would reveal what the surface is made of and how far prebiotic chemistry has progressed in environments that provide known key ingredients for life, identifying the chemical building blocks available and processes at work to produce biologically relevant compounds.”
In addition, Dragonfly would also use remote-sensing observations to characterize the geology of landing sites. In addition to providing context for the samples, it would also allow for seismic studies to determine the structure of the Titan and the presence of subsurface activity. Last, but not least, Dragonfly would use meteorology sensors and remote-sensing instruments to gather information on the planet’s atmospheric and surface conditions.
In the latter category, you have concepts like the Titan Saturn System Mission (TSSM), a concept that was being jointly-developed by the European Space Agency (ESA) and NASA. An Outer Planets Flagship Mission concept, the design of the TSSM consisted of three elements – a NASA orbiter, an ESA-designed lander to explore Titan’s lakes, and an ESA-designed Montgolfiere balloon to explore its atmosphere.
What separates Dragonfly from these and other concepts is its ability to conduct aerial and ground-based studies with a single platform. As Dr. Turtle explained:
“Dragonfly would be an in situ mission to perform detailed measurements of Titan’s surface composition and conditions to understand the habitability of this unique organic-rich ocean world. We proposed a rotorcraft to take advantage of Titan’s dense, calm atmosphere and low gravity (which make flight easier on Titan than it is on Earth) to convey a capable suite of instruments from place to place — 10s to 100s of kilometers apart — to make measurements in different geologic settings. Unlike other aerial concepts that have been considered for Titan exploration (of which there have been several), Dragonfly would spend most of its time on the surface performing measurements, before flying to another site.”
Dragonfly‘s suite of instruments would include mass spectrometers to study the composition of the surface and atmosphere; gamma-ray spectrometers, which would measure the composition of the subsurface (i.e. looking for evidence of an interior ocean); meteorology and geophysics sensors, which would measure wind, atmospheric pressure, temperature and seismic activity; and a camera suite to snap pictures of the surface.
Given Titan’s dense atmosphere, solar cells would not be an effective option for a robotic mission. As such, the Dragonfly would rely on a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) for power, similar to what the Curiosity rover uses. While robotic missions that rely on nuclear power sources are not exactly cheap, they do enable missions that can last for years at a time and conduct invaluable research (as Curiosity has shown).
As Peter Bedini – the Program Manager at the JHUAPL Space Department and Dragonfly’s project manager – explained, this would allow for a long-term mission with significant returns:
“We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons. However, we can multiply the value of the mission if we add aerial mobility, which would enable us to access a variety of geologic settings, maximizing the science return and lowering mission risk by going over or around obstacles.”
In the end, a mission like Dragonfly would be able to investigate how far prebiotic chemistry has progressed on Titan. These types of experiments, where organic building blocks are combined and exposed to energy to see if life emerges, cannot be performed in a laboratory (mainly because of the timescales involved). As such, scientists hope to see how far things have progressed on Titan’s surface, where prebiotic conditions have existed for eons.
In addition, scientists will also be looking for chemical signatures that indicate the presence of water and/or hydrocarbon-based life. In the past, it has been speculated that life could exist within Titan’s interior, and that exotic methanogenic lifeforms could even exist on its surface. Finding evidence of such life would challenge our notions of where life can emerge, and greatly enhance the search for life within the Solar System and beyond.
As Dr. Turtle indicated, mission selection will be coming soon, and whether or not the Dragonfly mission will be sent to Titan should be decided in just a few years time:
“Later this fall, NASA will select a few of the proposed New Frontiers missions for further work in Phase A Concept Studies” she said. “Those studies would run for most of 2018, followed by another round of review. And the final selection of a flight mission would be in mid-2019… Missions proposed to this round of the New Frontiers Program would be scheduled to launch before the end of 2025.”
And be sure to check out this video of a possible Dragonfly mission, courtesy of the JHUAPL:
Last week – from Monday, February 27th to Wednesday, March 1st – NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. In the course of the many presentations, speeches and panel discussions, NASA’s shared its many plans for the future of space exploration with the international community.
Among the more ambitious of these was a proposal to explore Titan using an aerial explorer and a lander. Building upon the success of the ESA’s Cassini-Huygen mission, this plan would involve a balloon that would explore Titan’s surface from low altitude, along with a Mars Pathfinder-style mission that would explore the surface.
Ultimately, the goal a mission to Titan would be to explore the rich organic chemical environment the moon has, which presents a unique opportunity for planetary researchers. For some time, scientists have understood that Titan’s surface and atmosphere have an abundance of organic compounds and all the prebiotic chemistry necessary for life to function.
“Titan’s of particular interest because the abundant and complex organic chemistry can teach us about chemical interactions that could have occurred here on Earth (and elsewhere?) leading to the development of life. Furthermore, not only does Titan have an interior liquid-water ocean, but there will also have been opportunities for organic material to have mixed with liquid water at Titan’s surface, for example impact craters and possibly cryovolcanic eruptions. The combination of organic material with liquid water, of course, increases astrobiological potential.”
For this reason, the exploration of Titan has been a scientific goal for decades. The only question is how best to go about exploring Titan’s unique environment. During previous Decadal Surveys – such as the Campaign Strategy Working Group (CSWG) on Prebiotic Chemistry in the Outer Solar System, of which Lorenz was a contributor – has suggested that a mobile aerial vehicle (such as an airship or a balloon) would well-suited to the task.
However, such vehicles would be unable to study Titan’s methane lakes, which are one of the most exciting draws of the moon as far as research into prebiotic chemistry goes. What’s more, an aerial vehicle would not be able to conduct in-situ chemical analysis of the surface, much like what the Mars Exploration Rovers (Spirit, Opportunity and Curiosity) have been doing on Mars – and with immense results!
At the same time, Lorenz and his colleagues examined concepts for the exploration of Titan’s hydrocarbon seas – like the proposed Titan Mare Explorer (TiME) capsule. As one of several finalists of NASA’s 2010 Discovery competition, this concept called for the deployment of nautical robot to Titan in the coming decades, where it would study its methane lakes to learn more about the methane cycle and search for signs of organic life.
While such a proposal would be cost-effective and presents some very exciting opportunities for research, it also has some limitations. For instance, during the 2020s-2030s, Titan’s northern hemisphere will be experiencing its winter season; at which point the thickness of its atmosphere will make direct-to-Earth communications and Earth views impossible. On top of that, a nautical vehicle would preclude the exploration of Titan’s land surfaces.
These offer some of the most likely prospects for studying Titan’s advanced chemical evolution, including Titan’s dune sands. As a windswept region, this area likely has material deposited from all over Titan and may also contain aqueously altered materials. Much as the Mars Pathfinder landing site was selected so it could collect samples from a wide area, such as location would be an ideal site for a lander.
As such, Lorenz and his colleagues advocated the type of mission that was articulated in the 2007 Flagship Study, which called for a Montgolfière balloon for regional exploration and a Pathfinder-like lander. This would provide the opportunity to conduct surface imaging at resolutions that are impossible from orbit (due to the thick atmosphere) as well as investigating the surface chemistry and interior structure of the moon.
So while the balloon would gather high-resolution geographical data of the moon, the lander could conduct seismological surveys that would characterize the thickness of the ice above Titan’s internal water ocean. However, a lander mission would be limited in terms of range, and the surface of Titan presents problems for mobility. This would make multiple landers, or a relocatable lander, the most desired option.
“Potential targets include areas where we can measure solid surface materials, the composition of which is still not well known, Titan’s dune sands, for example,” said Turtle. “Detailed in situ analysis is required to determine their composition. The lakes and seas are also intriguing; however, in the nearer term (missions arriving in the 2030s) most of those will be in winter darkness. So, exploring them would likely have to wait until the 2040s.”
This mission concept would also take advantage of several technological advances that have been made in recent years. As Lorenz explained in the course of the presentation:
“Heavier-than-air mobility at Titan is in fact highly efficient, moreover, improvements in autonomous aircraft in the two decades since the CSWG make such exploration a realistic prospect. Multiple in-situ landers delivered by an aerial vehicle like an airplane or a lander with aerial mobility to access multiple sites, would provide the most desirable scientific capability, highly relevant to the themes of origins, workings, and life.”
However, addressing some additional challenges not raised at the 2050 Vision Workshop, they will be presenting a slight twist on their idea. Instead of a balloon and multiple landers, they will present a mission concept involving a “Dragonfly” qaudcopter. This four-rotor vehicle would be able to take advantage of Titan’s thick atmosphere and low gravity to obtain samples and determine the surface composition in multiple geological settings.
This concept also incorporates a lot of recent advances in technology, which include modern control electronics and advances in commerical unmanned aerial vehicle (UAV) designs. On top of that, a quadcopter would do away with chemically-powered retrorockets and could power-up between flights, giving it a potentially much longer lifespan.
These and other concepts for exploring Saturn’s moon Titan are sure to gain traction in the coming years. Given the many mysteries locked away on this world – with includes abundant water ice, prebiotic chemistry, a methane cycle, and a subsurface ocean that is likely to be a prebiotic environment – it is certainly a popular target for scientific research.
Portrait of Curiosity assembled from raw images acquired with MAHLI on Sol 85 (Nov. 11. 2012 UTC) Credit: NASA/JPL-Caltech/Malin Space Science Systems. Composite by Jason Major.
Yesterday Mars Science Laboratory principal investigator John Grotzinger set the entire space science world abuzz with a tantalizing promise of “earthshaking” news on the horizon — literally “one for the history books,” as he put it in an interview with NPR. It seems one of Curiosity’s main science tools, the Sample Analysis at Mars (SAM) instrument, has discovered… something… within recently-gathered samples, possibly in windblown-material scooped at a site called “Rocknest” earlier this month.
For now, though, the MSL team is keeping quiet on any more details until they’re reasonably sure they know what they have. Speculations abound — some serious, some not — but the bottom line is we’ll all have to wait for the official news to be released. In the meantime, here’s your chance to learn a little more about a fascinating high-tech Mars-tasting gadget called SAM.
About the size of a window air conditioning unit, the Sample Analysis at Mars (SAM) instrument is contained within the front section of NASA’s Curiosity rover. Actually a suite of three instruments, SAM consists of a Gas Chromatograph (GC), a Quadrupole Mass Spectrometer (QMS), and a Tunable Laser Spectrometer (TLS), as well as systems that manipulate and process samples.
Annotated photo of SAM with side covers removed
Although mostly contained entirely within Curiosity, SAM does have two small inlet tubes that allow access for soil samples gathered with the rover’s arm, as well as inlets for atmospheric gases.
On Earth all of these different instruments would fill a lab. But to fit them all inside the Curiosity, which is about the size of a Mini Cooper (but only half the mass), they were painstakingly reduced in size to fit within a single rectangular structure about 40 kg (88 lbs).
Here’s how SAM’s components work:
The Gas Chromatograph (GC)
The GC has six complementary chromatographic columns. The GC assembly sorts, measures, and identifies gases it separates from mixtures of gases by pushing the mixed gases through long, coiled tubes with a stream of helium gas. It sorts the gas molecules by weight: they emerge from the tube in order from lightest (out first) to heaviest (out last). Once the gases are sorted, the GC can direct quantities of the separated gases into the QMS or TLS for further analysis.
The Quadrupole Mass Spectrometer (QMS)
The QMS identifies gases by the molecular weight and electrical charge of their ionized states. It fires high-speed electrons at the molecules, breaking them into fragments. It then sorts the fragments by weight with AC and DC electric fields. The spectra generated by the QMS detector uniquely identify the molecules in the gases.
The Tunable Laser Spectrometer (TLS)
The TLS uses absorption of light at specific wavelengths to measure concentrations and isotope ratios of specific chemicals important to life: methane, carbon dioxide, and water vapor. Isotopes are variants of the same element with different atomic weights, and their ratios can provide information about Mars’ geologic — and possibly biologic — history.
The QMS and the GC can operate together in a GCMS mode for separation and definitive identification of organic compounds. The TLS obtains precise isotope ratios for C and O in carbon dioxide and measures trace levels of methane and its carbon isotope.
In addition to these three analytical instruments SAM also has mechanical support devices: a sample manipulation system (SMS) and a Chemical Separation and Processing Laboratory (CSPL). The CSPL includes high conductance and micro valves, gas manifolds with heaters and temperature monitors, chemical and mechanical pumps, carrier gas reservoirs and regulators, pressure monitors, pyrolysis ovens, and chemical scrubbers and getters.
The SMS has a wheel of 74 small cups where soil samples gathered by Curiosity’s robotic arm are prepared for analysis. 59 are quartz cups that are small ovens which can be heated to very high temperatures to pull gases from the powdered samples. 9 sealed cups are filled with chemical solvents for lower-temperature experiments designed to search for organic compounds. The other 9 cups contain calibration materials.
With this suite of precision tools SAM is specifically designed to search for evidence of a habitable environment on Mars, whether past or present. As it takes up over half of the rover’s scientific payload area, you could say that Curiosity itself is specifically designed to carry SAM around Mars (although we won’t tell that to the other instruments!)
Knowing only that the “exciting” news from Grotzinger and his team is coming from data gathered by SAM, one could safely assume that it has something to do with a discovery of organic chemistry of some sort… but we’ll all have to wait a few more weeks to know for sure. Still, as that is the primary objective of MSL and Curiosity is barely over 100 Martian days into its mission, even the smallest hint of big news has everyone’s attention.
Like any big institution, NASA would love to trumpet a major finding, especially at a time when budget decisions are being made.
(And for an even more in-depth look at how SAM works, read Emily Lakdawalla’s article on The Planetary Society’s blog here.)
The result of an international effort between scientists and engineers, SAM was built and tested at NASA Goddard Space Flight Center in Greenbelt, Maryland. Paul Mahaffy is SAM’s Principal Investigator.
UPDATE: Apparently the NPR article that kickstarted all the rumors of big discoveries from Curiosity was a big misunderstanding… while data from the rover is “one for the history books,” according to P.I. John Grotzinger, that pertained to the mission as a whole — not any individual finding. Still, news from the MSL mission will be presented on Dec. 3 at the American Geophysical Union conference in San Francisco.
“Rumors and speculation that there are major new findings from the mission at this early stage are incorrect… At this point in the mission, the instruments on the rover have not detected any definitive evidence of Martian organics.” – JPL news release, Nov. 29, 2012