The Dragonfly drone will make multiple flights over Titan, and explore the moon's surface during periodic landings.Credit: Johns Hopkins APL

NASA will send a dual-quadcopter drone to hop across the surface of Titan, Saturn’s largest moon, the agency announced on 27 June. Named Dragonfly, the mission will launch in 2026 and arrive at Titan in 2034.

“Dragonfly is really a Mars-rover-sized drone that we’ll be able to fly from place to place on Titan,” says Elizabeth Turtle, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, who leads the mission.

The nuclear-powered Dragonfly can fly tens of kilometres in less than an hour, allowing it to cover ground much faster than a wheeled rover could. Over the course of a two-year mission, the drone could traverse hundreds of kilometres.

Hydrocarbon-rich clouds in Titan’s atmosphere rain methane and ethane onto the moon’s surface. The liquid collects in lakes and seas, which NASA’s Cassini spacecraft saw glimmering in sunlight in at various points from 2009 to 2017. Some of the lakes grow and shrink as seasons change on Titan.

Dragonfly will study the atmosphere as it flies around, and touch down for extended stays on the moon's surface. The drone will explore areas where methane- and ethane-rich lakes recently dried up — and in the process, might have left behind residue rich with organic compounds like those that may have existed on early Earth before life arose. "Titan has all of the key ingredients needed for life," says Lori Glaze, head of NASA's planetary sciences division.

Hop, skip and a jump

In 2005, the European Space Agency’s Huygens probe became the first spacecraft to land on Titan. It measured the temperature, pressure, and density of Titan’s atmosphere during its descent, and sent back pictures of the rugged, rocky landscape for 72 minutes after it touched down.

Dragonfly beat out a proposed mission to return a sample from Comet 67P/Churyumov-Gerasimenko, which the European Space Agency’s Rosetta spacecraft explored between 2014 and 2016. The Comet Astrobiology Exploration SAmple Return (CAESAR) project is led by Steve Squyres, a planetary scientist at Cornell University in Ithaca, New York. It would bring back at least 80 grams of material from 67P’s nucleus, by far the largest sample ever taken from a comet. NASA’s Stardust mission gathered about a microgram of dust from Comet Wild 2 in 2004.

Dragonfly is part of NASA's New Frontiers programme, which selects its planetary-science missions from proposals submitted by researchers that are subject to price limits. Dragonfly’s cost is capped at US$850 million in 2015 dollars — not including the mission's launch vehicle.

The three prior New Frontiers missions are New Horizons, which flew past Pluto in 2015 and a smaller rock in the outer Solar System earlier this year; Juno, which has been orbiting Jupiter since 2016; and OSIRIS-REx, which is circling the asteroid Bennu and will collect a sample of it next year to fly back to Earth. </s> Something to look forward to: Yesterday, NASA shared the details of its next big mission to explore our Solar System, called Dragonfly. A drone lander mission to Titan, Saturn's largest moon which the space agency says is unlike any other place in our Solar System and is similar to how the Earth was in its early days.

The richly organic world of Titan is the next destination for NASA's newly announced Dragonfly mission. The drone powered by 8 rotors will begin its flight in 2026 and land on Saturn's moon in 2034 after travelling a distance of 840 million miles. Taking advantage of Titan's dense atmosphere, which is 4 times denser than Earth, the rotorcraft will fly to dozens of locations helped by 13 years worth of data from the Cassini spacecraft that met its fate 2 years ago.

The drone will look for "prebiotic chemical processes common on both Titan and Earth," and marks the first time in NASA's history in which it'll be using a multi-rotor vehicle for scientific study on another planet. It will also "become the first vehicle ever to fly its entire science payload to new places for repeateable and targeted access to surface materials."

The fourth mission selected as part of the agency's NEW Frontiers program that includes the New Horizon mission to Pluto and the Kuiper Belt, Jupiter's Juno and the Bennu orbiting OSIRIS-REx, is being led by Elizabeth Turtle of the Johns Hopkins University Applied Physics Laboratory. These programs are capped at $1 billion each and selected from a competition held among multiple government and academic institutions.

Upon landing on Titan's surface, the drone will spend 2.7 years as part of its baseline mission in which it will "explore diverse environments from organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years."

During its baseline mission, Dragonfly will be capable of flying over Titan's surface at about 20mph (32.1 km/h) reaching altitudes of up to 2 miles (3.2 km), where a single day goes by in about 16 Earth days. Upon reaching a low-altitude impact crater called Selk, the baseline mission will conclude. "We know this area quite well, there's a lot of data from different instruments in this region," says Elizabeth. "We will take images with both downward-looking cameras along the ground track underneath Dragonfly as we fly over the surface, as well as forward-looking cameras, so we’ll be able to look out toward the horizon as well."

Titan's atmosphere is nitrogen-based like Earth but unlike our home, it has clouds and rain of methane. "The moon's weather and surface processes have combined complex organics, energy, and water similar to those that may have sparked life on our planet."

Appreciating the New Frontiers program for its transformation in the understanding of our Solar System, director of NASA's Planetary Science Division, Lori Glaze, highlighted achievements of the previous and on-going missions with Dragonfly which will "add Titan to the list of enigmatic worlds NASA will explore." </s> We're going to Titan, and we're going in style. NASA announced on Thursday its next great solar system exploration mission. "Dragonfly" involves an ambitious plan to send a rotorcraft -- essentially a large drone -- to Saturn's moon, Titan. The flying vehicle will be designed to touch down in multiple locations, from dunes to the floor of an impact crater carrying out science missions to look for the building blocks of life.

Titan is an icy land of wonder and intrigue, home to massive methane lakes and mysterious disappearing islands. It's the second largest moon in the solar system. NASA calls it an analogue to the very early Earth and at least one NASA engineer has suggested we look to Titan for a future human colony.

"Dragonfly will visit a world filled with a wide variety of organic compounds, which are the building blocks of life and could teach us about the origin of life itself," said NASA's Thomas Zurbuchen.

Dragonfly will aim for a 2.7-year initial mission, with dozens of landing sites on the menu. "Dragonfly marks the first time NASA will fly a multirotor vehicle for science on another planet; it has eight rotors and flies like a large drone," NASA said.

NASA engineers are gearing up Dragonfly to cover more than 108 miles (around 175 kilometers) of Titan's surface. That would make it one of the most accomplished interplanetary robots, nearly doubling the distance which all of the Mars rovers (combined!) have traveled to date.

The Titan mission is made possible in part by NASA's dearly departed Cassini spacecraft, which studied Titan while it was investigating Saturn. Cassini helped NASA scientists delve into potential Titan landing sites.

NASA plans to launch Dragonfly in 2026, which would put it on track to arrive at Titan in 2034. The mission is part of the agency's New Frontiers program, which includes the New Horizons mission to Pluto (and beyond) and the Juno mission to Jupiter.

The program originally selected two finalists for the next New Horizons mission in December 2017. The unlucky second finalist was the Comet Astrobiology Exploration Sample Return (Caesar) mission, which aimed to send a spacecraft to the comet 67P/Churyumov–Gerasimenko and return a sample to Earth.

The comet was the destination of the European Space Agency's Rosetta spacecraft, which rendezvoused with the space rock in 2014. It even landed a smaller spacecraft, Philae, on the surface, providing us with some stunning images.

Titan is a worthy target because it is really strange but its atmosphere and environment contains molecules that could have kick-started life as we know it. That doesn't mean we will find a race of purple Titans on the icy moon -- and certainly not any particularly mad ones, either -- but it may tell us a thing or two about how life starts.

"Visiting this mysterious ocean world could revolutionize what we know about life in the universe," said NASA administrator Jim Bridenstine.

Update, 7:13 p.m.: Adds more context about New Horizons mission. </s> NASA announced the latest mission in its New Frontiers program, called Dragonfly, which will explore Saturn’s largest moon, Titan. It’s the only moon in our solar system that has an atmosphere.

Before it ended in 2017, the Cassini mission flew by Titan while studying Saturn. The data provided by the Hyugens probe, which was part of the Cassini mission, suggested that Titan was the perfect candidate for further exploration.

“It’s the first drone lander and it can fly over 100 miles through Titan’s thick atmosphere,” said NASA Administrator Jim Bridenstine in a statement. “Titan is most comparable to early Earth. Dragonfly’s instruments will help evaluate organic chemistry and the chemical signatures of past or present life. We will launch Dragonfly to explore the frontiers of human knowledge for the benefit of all humanity.”

The New Frontiers program has also included the Juno mission to Jupiter, the New Horizons probe that visited Pluto in 2015 and distant Kuiper Belt Object Ultima Thule on January 1.

The ultimate goal is for Dragonfly to visit an impact crater, where they believe that important ingredients for life mixed together when something hit Titan in the past, possibly tens of thousands of years ago.

Titan is similar chemically to Earth before life evolved, the agency said. They want to explore sand dunes on Titan to determine if they’re made of the same complex organic material discovered in the atmosphere.

“It’s the science that motivates us to do this exciting and difficult mission,” said Thomas Zurbuchen, NASA’s associate administrator for Science at the agency’s Headquarters in Washington.

“Titan has the key ingredients for life,” said Lori Glaze, director of NASA’s Planetary Science Division. “It has complex organic molecules and the energy required for life. We will have the opportunity to observe processes similar to what happened on early Earth when life formed and potentially conditions that could harbor life today. We can look for biosignatures.”

Once Dragonfly lands, it will spend two and a half years flying around Titan. It only has propellers, with skids to land, but no wheels to allow it to roam over the surface.

It will launch in 2026, but won’t reach Titan until the 2034 because Saturn is so far from us.

Dragonfly will also explore Titan’s atmosphere, surface properties, subsurface ocean and liquid on the surface.

Titan isn’t exactly known for being hospitable.

Larger than both our own moon and the planet Mercury, Titan is unique in our solar system. It is the only moon with clouds and a dense atmosphere of nitrogen and methane, which gives it a fuzzy orange appearance.

Its atmospheric pressure is 60% greater than Earth’s, meaning it exerts the kind of pressure you feel at the bottom of a swimming pool, according to NASA. And the surfaceof Titan is minus 290 degrees Fahrenheit.

So it would make sense that the potential for life on Titan would have to look a little different than our planet. But Titan’s atmosphere may not be much different than that of primordial Earth’s — and life found a way here.

It may not be like the alien life in science fiction, but in 2017 researchers confirmed the presence of something that may lead to life on Titan, according to a study published Friday in the journal Science Advances.

Vinyl cyanide is a complex organic molecule capable of forming cell membrane-like spheres. While it may sound toxic, this chemical would be right at home on Titan, where significant quantities of it have been detected through data from the Atacama Large Millimeter Array (ALMA), a group of radio telescopes in Chile.

Titan also has Earth-like liquid bodies on its surface, but the rivers, lakes and seas are made of liquid ethane and methane, which form clouds and cause liquid gas to rain from the sky.

The surface temperature is so cold that the rivers and lakes were carved out by methane, the way rocks and lava helped to form features and channels on Earth.

These methane pools on the surface are the kind of environment that could help vinyl cyanide molecules link together to form cell-like membranes, not unlike the basis for organisms on Earth.

“The presence of vinyl cyanide in an environment with liquid methane suggests the intriguing possibility of chemical processes that are analogous to those important for life on Earth,” said Maureen Palmer, lead study author and researcher at NASA’s Goddard Space Flight Center.

The ALMA data confirmed what previous studies and simulations, like one from Cornell University in 2015, had predicted about the potential presence of this molecule on Titan.

“Researchers definitively discovered the molecule, vinyl cyanide. That is our best candidate for a ‘protocell’ that might be stable and flexible in liquid methane,” said Jonathan Lunine, a Cornell professor who participated in the 2015 study. “This is a step forward in understanding whether Titan’s methane seas might host an exotic form of life.”

Titan is also believed to have an internal liquid water ocean, like those on Europa, one of Jupiter’s moons, and Enceladus, another of Saturn’s moons. Earlier this year, NASA announced that Europa and Enceladus’ oceans have some or most of the ingredients necessary for life as we know it.

But how does Titan compare? First of all, it’s bigger than Europa and Enceladus. It’s also entirely unique in its possession of a dense atmosphere, which has obscured the observations that researchers have tried to make of Titan. And Titan doesn’t have confirmed active geysers on its surface like those other moons.

Given its complex chemistry, it’s safe to say that Titan isn’t hospitable to humans. But it is attractive to researchers.

“Saturn’s moon, Enceladus, is the place to search for life like us, life that depends on — and exists in — liquid water,” Lunine said. “Titan, on the other hand, is the place to go to seek the outer limits of life — can some exotic type of life begin and evolve in a truly alien environment, that of liquid methane?” </s> NASA will fly a billion-dollar quadcopter to Titan, Saturn’s methane-rich moon

The siren call of Titan could not be ignored. NASA’s next billion-dollar mission, called Dragonfly, will be an innovative quadcopter to explore Titan, Saturn’s largest moon, the agency announced today. The craft will soar and hover over the icy moon’s surface—and land on it—in a search for the conditions and chemistry that could foster life.

The mission—led by Elizabeth “Zibi” Turtle, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, and also managed by APL—will launch in 2026. It represents a calculated risk for the agency, embracing a new paradigm of robotic exploration to be used on a distant moon. “Titan is unlike any other place in the solar system, and Dragonfly is like no other mission,” said Thomas Zurbuchen, NASA’s associate administrator for science in Washington, D.C., while announcing the mission’s selection. “The science is compelling. It’s the right time to do it.”

Titan is veiled by a nitrogen atmosphere and larger than Mercury. It is thought to harbor a liquid ocean beneath its frozen crust of water ice. NASA’s Cassini spacecraft studied Titan during its historic campaign, and, in 2005, dropped the short-lived Huygens probe into Titan’s atmosphere.

The surface it saw had many geologic features similar to those found on Earth, including plateaus, dune-filled deserts, and, at its poles, liquid seas and rivers. But on Titan, where temperatures average a frigid 94 K, the “rocks” are made of water ice and the seas are filled with ethane and methane, hydrocarbons that are gases on Earth. The moon’s stew of organic molecules and water, many scientists believe, could have resulted in reactions to create amino acids and the bases used to build DNA’s double helix. It’s as if Titan has been conducting experiments on life formation for millions of years, Turtle says. “Dragonfly is designed to go pick up the results of those experiments and study them.”

Dragonfly is an inspiring selection, adds Lindy Elkins-Tanton, a planetary scientist at Arizona State University in Tempe and principal investigator of Psyche, NASA’s mission to a metallic asteroid. “Titan might truly be the cradle for some kind of life—and whether life has emerged or not, Titan’s hydrocarbon rivers and lakes, and its hydrocarbon snow, makes it one of the most fantasylike landscapes in our solar system.”

Given Titan’s complex surface, a lander at a single site would not be able to say much about the moon’s chemistry. Dragonfly leverages the advances in computing and aircraft design that have led to the explosion of hovering drones on Earth. It will carry eight rotor blades, on the top and bottom of each of four arms. It is, in effect, a movable lander, capable of shunting kilometers between sampling sites every 16 Earth days. Titan’s dense air and low gravity will allow the 300-kilogram, sedan-size copter, which will be powered by a radioactive generator, to hover with 38 times less power than needed on Earth.

The timing of Dragonfly’s arrival, in 2034 during Titan’s long northern winter, ruled out a landing near the north pole, home to the moon’s evocative methane seas; those sites would leave it unable to radio home. Instead, the quadcopter will explore the moon’s vast equatorial deserts, which are likely fed by a grab bag of material from all over the moon. (“The largest zen garden in the solar system,” Turtle says.) It will search especially for impact craters or ice volcanoes, energetic processes that could provide a spark—and the liquid water—needed for nascent organic chemistry. During its nearly 3-year primary mission, after traveling 175 kilometers in a series of flights lasting up to 8 kilometers each, Dragonfly will ultimately reach the 80-kilometer-wide Selk impact crater, its primary target. The impact that created Selk was large enough to melt Titan’s water-ice crust and liberate oxygen, priming reactions that are recorded in its outcrops.

Dragonfly won’t be equipped with a robotic arm, like the recent Mars rovers. Its exploration will first be guided by an instrument on its belly that will bombard the ground with neutron radiation, using the gamma rays this attack releases to differentiate between basic terrain types, such as ammonia-rich ice or carbon-rich sand dunes. Its two landing skids will also each carry a rotary-percussive drill capable of taking samples and feeding them through a pneumatic tube to a mass spectrometer that can analyze their composition. The sampling system represented a risk for the mission; NASA scientists were concerned Titan’s hydrocarbon-rich atmosphere could clog it, Zurbuchen says. “It’s the oil spill version of an atmosphere.” Over the past 2 years, after extensive testing with “pathological” materials and a redesign, Turtle says, the agency’s fears were allayed.

Beyond Titan’s surface, Dragonfly will also target its atmosphere and interior. During flight, it can collect measurements, much like instruments mounted on a balloon would. And it is also equipped with a seismometer that could use vibrations induced on the moon by its tidal lock with Saturn to gauge the ocean hidden beneath its crust, which scientists have suggested could be made up of ammonia-water or water and sulfate. Ultimately, the quadcopter’s explorations may be able to last up to 8 years after landing before its nuclear power source peters out.

The cost-capped New Frontiers program, with $850 million set for the mission and some $150 million for launch, is the largest planetary exploration line that NASA opens to outside competition and leadership. A significant factor in Dragonfly’s selection, Zurbuchen adds, was APL’s ability to deliver the Parker Solar Probe, now on a mission to explore the sun that's on time and under budget. Dragonfly went head-to-head with one other finalist, the Comet Astrobiology Exploration Sample Return, which would have sampled primordial ice from a comet and returned it for study on Earth. </s> NASA selected the next mission in its New Frontiers program today: a drone that will fly on Saturn’s moon Titan in 2034. Dragonfly, as the eight-rotored craft is called, will aim to investigate the distant world’s strange geology—a previous probe glimpsed rivers of liquid methane flowing on the surface—and to search for signs of alien life.

The idea is for Dragonfly to launch from Earth in 2026, and then zip past Venus and make two flybys of Earth to pick up speed for the long trip to Saturn. Dragonfly won’t enter orbit before heading to the surface—it’ll be a precisely aimed shot at the edge of the Selk crater, just north of Titan’s equator. Once inside Titan’s thick atmosphere, Dragonfly will drift downward for hours under a series of parachutes until it’s about 1km above the surface. It will then cut away and fly off in search of a good landing site.

Radio signals take over an hour to make a one-way trip between Saturn and Earth, which means Dragonfly will have to fly autonomously. NASA officials are confident it can do so reliably because of the remarkable advances in autonomous flight and hazard-detection capability achieved by drones on Earth in recent years. It helps a great deal that Titan has been well-scouted by the Cassini mission, which orbited Saturn from 2004 until 2017 and landed a probe on Titan’s surface (the most distant landing ever to take place).

The drone will have 8 rotors stacked in 4 pairs, and will be designed to be able to fly even if one rotor fails. Each rotor will be about a meter long. Because of Titan’s dense (over 4 times denser than Earth’s) atmosphere and low gravity, it takes about 40 times less power to fly there than on Earth. Not that conditions are hospitable in all ways. It will also be cold: about minus 180 degrees Celsius (minus 290 degrees Fahrenheit).

The initial landing spot has been carefully chosen. The Selk crater region will be in a direct line of site from Earth, so Dragonfly will be able to communicate with NASA’s Deep Space Network antennas in California, Spain, and Australia without a relay satellite. That makes the mission both simpler and cheaper. Dragonfly will have a foldable antenna to transmit images and scientific data back to Earth after landing on sand dunes that Zibi Turtle of the Applied Physics Laboratory at Johns Hopkins University, who will head the mission, describes as “the largest zen gardens in the solar system."

Solar power wouldn’t work well, because of the distance from the Sun and Titan’s hazy atmosphere, so Dragonfly will carry a generator that uses heat from the radioactive decay of about 4kg of plutonium to create electricity. That won’t be enough to effectively power the 8 rotors, so the generator will charge a battery that will in turn power the drone’s engines.

The initial plan is for a few dozen flights over the course of a bit more than two and a half years. Dragonfly will be able to hop short distances if it lands in an awkward place. But the exploratory flights will be up to five miles each, in a “leapfrog” pattern that will let it scout out good landing sites before committing to them.

Dragonfly will be more than just a joyride—it’s out to settle a number of scientific debates. It will carry a seismometer that can listen for tremors and help determine how thick the ice shell over Titan’s liquid water ocean is. It will have meteorological instruments and cameras. Cassini also found some evidence that suggests Titan may play host to “cryovolcanoes”—mountains of ice that spew some mixture of water, methane and ammonia into the atmosphere. Dragonfly will try to figure out whether or not such eruptions indeed happen.

Then there’s the big question: is there now, or has there ever been, life on Titan? Dragonfly will carry a suite of scientific instruments meant to address this question.

One instrument will shoot pulses of neutrons into Titan’s surface to ascertain how much carbon, nitrogen, hydrogen, and oxygen lie below. This pulsed-neutron generator will kick up radiation that will then be detected by two pairs of redundant spectrometers. If those spectrometers find hints of something interesting, two on-board drills will get to work. A sort of vacuum cleaner will suck up the drill cuttings (and other types of samples), which will be examined more closely, especially for purines and pyrimidines—the bases that make up DNA—and for amino acids.

Getting all of these instruments to work reliably in an atmosphere literally dripping with methane will be difficult. But, Turtle says, they are reusing lots of components that have already been functioning on Mars for years. “Titan is a very Earth-like place, despite the fact that the materials are different,” she says. Just how Earth-like? That’s what Dragonfly aims to find out. </s> Before it ended in 2017, the Cassini mission flew by Titan while studying Saturn. The data provided by the Hyugens probe, which was part of the Cassini mission, suggested that Titan was the perfect candidate for further exploration.

"It's the first drone lander and it can fly over 100 miles through Titan's thick atmosphere," said NASA Administrator Jim Bridenstine in a statement. "Titan is most comparable to early Earth. Dragonfly's instruments will help evaluate organic chemistry and the chemical signatures of past or present life. We will launch Dragonfly to explore the frontiers of human knowledge for the benefit of all humanity."

The New Frontiers program has also included the Juno mission to Jupiter, the New Horizons probe that visited Pluto in 2015 and distant Kuiper Belt Object Ultima Thule on January 1.

The ultimate goal is for Dragonfly to visit Celt Crater, where they believe that important ingredients for life mixed together when something impacted Titan.

Titan is similar chemically to Earth before life evolved, the agency said. They want to explore sand dunes on Titan to determine if they're made of the same organic discovered in the atmosphere. "It's the science that motivates us to do this exciting and difficult mission," said Thomas Zurbuchen, NASA's associate administrator for Science at the agency's Headquarters in Washington. "Titan has the key ingredients for life," said Lori Glaze, director of NASA's Planetary Science Division. "It has complex organic molecules and the energy required for life. We will have the opportunity to observe processes similar to what happened on early Earth when life formed and potentially conditions that could harbor life today. We can look for biosignatures." Once Dragonfly lands, it will spend two and a half years flying around Titan. It only has propellers, with skids to land, but no wheels to allow it to roam over the surface. It will launch in 2026, but won't reach Titan until the 2034 because Saturn is so far from us. </s> Nasa to fly a drone to Saturn’s moon Titan in search of signs of life </s> “We will be flying initially over dunes and then into rugged terrain,” said Elizabeth Turtle, who will lead the mission for the lab as its principal investigator. “We will take images with both downward-looking cameras along the ground track underneath Dragonfly as we fly over the surface, as well as forward-looking cameras, so we’ll be able to look out toward the horizon as well.”

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Titan has long intrigued planetary scientists. On Christmas Day 2004, NASA’s Cassini spacecraft sent a probe, Huygens, to the moon’s surface. It landed in one piece, revealing a world analogous to a primordial Earth — Dr. Turtle described it as, “eerily familiar on such a different and exotic world.” Rather than water, Titan’s seas are filled with liquid methane.

In addition to a camera, Dragonfly will carry an assortment of scientific instruments: spectrometers to study Titan’s composition; a suite of meteorology sensors; and even a seismometer to detect titanquakes when it lands on the ground. Drills in the landing skids will collect samples of the Titan surface for onboard analysis.

“Titan is an incredibly unique opportunity scientifically,” Dr. Turtle said in an interview in April before NASA’s announcement. “Not only is it an ocean world — an icy satellite with a water ocean in its interior — but it is the only satellite with an atmosphere. And the atmosphere at Titan has methane in it, which leads to all sorts of rich organic chemistry happening at even the upper reaches of the atmosphere.”
NASA awards $1 billion to the Dragonfly mission, which will use a dual-quadcopter drone to explore Titan for signs of life.