"NASA's Ingenuity Mars Helicopter has emerged from its first night on the surface of Mars," reports NASA's Jet Propulsion Laboratory. The Ingenuity Mars Helicopter was deployed from the belly of NASA's Perseverance rover on April 3rd. In the days to come, Ingenuity will be the first aircraft to attempt powered, controlled flight on another planet. From the report: Evening temperatures at Jezero Crater can plunge as low as minus 130 degrees Fahrenheit (minus 90 degrees Celsius), which can freeze and crack unprotected electrical components and damage the onboard batteries required for flight. "This is the first time that Ingenuity has been on its own on the surface of Mars," said MiMi Aung, Ingenuity project manager at NASA's Jet Propulsion Laboratory in Southern California. "But we now have confirmation that we have the right insulation, the right heaters, and enough energy in its battery to survive the cold night, which is a big win for the team. We're excited to continue to prepare Ingenuity for its first flight test."

To ensure the solar array atop the helicopter's rotors could begin getting sunlight as soon as possible, Perseverance was instructed to move away from Ingenuity shortly after deploying it. Until the helicopter put its four legs onto the Martian surface, Ingenuity remained attached to the belly of the rover, receiving power from Perseverance, which touched down at Jezero Crater on Feb. 18. The rover serves as a communications relay between Ingenuity and Earth, and it will use its suite of cameras to observe the flight characteristics of the solar-powered helicopter from "Van Zyl Overlook."

The moon is just 27% the size of earth. So long-time Slashdot reader fahrbot-bot shares an interesting question from Science Alert.

"If you were to hop in a spaceship, don a spacesuit and go on an epic lunar hike, how long would it take to walk all the way around it? " During the Apollo missions, astronauts bounced around the surface at a casual 1.4 mph (2.2 km/h), according to NASA. This slow speed was mainly due to their clunky, pressurized spacesuits that were not designed with mobility in mind. If the "moonwalkers" had sported sleeker suits, they might have found it a lot easier to move and, as a result, picked up the pace...

At this new hypothetical max speed, it would take about 91 days to walk the 6,786-mile (10,921 km) circumference of the moon. For context, it would take around 334 days to walk nonstop (i.e., not stopping to sleep or eat) around the 24,901-mile (40,075 km) circumference of Earth at this speed, although it is impossible to do so because of the oceans.

Obviously, it's not possible to walk nonstop for 91 days, so the actual walk around the moon would take much longer.
Of course, it's not that easy, with ongoing solar radiation, extreme temperatures, and the need to walk around mile-deep craters. Aidan Cowley, a scientific adviser at the European Space Agency, also pointed out to Live Science that you'd need a support vehicle following you with food, water, and oxygen (which could also double as shelter, "kind of like portable mini-bases."). But he also identified another issue: This type of mission would also require a huge amount of endurance training because of the demands of exercising in low gravity on your muscles and cardiovascular system. "You'd have to send an astronaut with ultra-marathon-level fitness to do it," Cowley said. Even then, walking at a top speed would be possible only for around three to four hours a day, Cowley said. So, if a person walked at 3.1 mph (5 km/h) for 4 hours a day, then it would take an estimated 547 days, or nearly 1.5 years to walk the moon's circumference, assuming your route isn't too disrupted by craters and you can deal with the temperature changes and radiation.

However, humans won't have the technology or equipment to accomplish such a feat until at least the late 2030s or early 2040s, Cowley said. "You'd never get an agency to support anything like this," Cowley said. "But if some crazy billionaire wants to try it, maybe they can pull it off."

In major international tests, the physics-defying EmDrive has failed to produce the amount of thrust proponents were expecting. In fact, in one test at Germany's Dresden University, it didn't produce any thrust at all. Is this the end of the line for EmDrive? Popular Mechanics: The crux of the EmDrive is if you bounce microwaves around inside the tube, they exert more force in one direction than the other, creating a net thrust without the need for any propellant. And when NASA and a team at Xi'an in China tried this, they actually got a small-but-distinct net force. Now, however, physicists at the Dresden University of Technology (TU Dresden) are saying those promising results showing thrust were all false positives that are explained by outside forces. The scientists recently presented their findings in three papers at Space Propulsion Conference 2020 +1, with titles like "High-Accuracy Thrust Measurements of the EmDrive and Elimination of False-Positive Effects." (Other two studies here and here)

Using a new measuring scale and different suspension points of the same engine, the TU Dresden scientists "were able to reproduce apparent thrust forces similar to those measured by the NASA team, but also to make them disappear by means of a point suspension," researcher Martin Tajmar told the German site GreWi. The verdict: "When power flows into the EmDrive, the engine warms up. This also causes the fastening elements on the scale to warp, causing the scale to move to a new zero point. We were able to prevent that in an improved structure. Our measurements refute all EmDrive claims by at least 3 orders of magnitude."

A new NASA mission, called the Double Asteroid Redirection Test (DART) mission due for launch this summer, aims to launch a spaceship that will directly punch an asteroid. Motherboard reports: The mission's target is an asteroid system called Didymos, which contains two space rocks that orbit each other. In late 2022, DART will forcefully impact the smaller asteroid in this system, a tiny moon called Dimorphos, so that scientists can assess the feasibility of knocking any space rocks that threaten Earth off course in the future. [...] DART will pioneer a subtler form of planetary defense, in which the trajectory of an asteroid is changed by a very small amount that becomes significant over time. Late next year, the mission will crash into Dimorphos at about seven kilometers per second. Shortly before the collision, the spacecraft will deploy a small satellite provided by the Italian Space Agency that is tasked with watching "the mess we make," [said Andy Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory and the investigation team lead for DART].

Observations from the Italian satellite, as well as from powerful telescopes on Earth, will reveal just how much Dimorphos was affected by the crash. Rivkin and his colleagues expect the change in orbital speed to be small -- about one millimeter per second -- which would add up to a shortening of the orbital period by about 10 minutes. But even this very slight shift would be enough to redirect the trajectory of a hazardous asteroid that threatened Earth, provided scientists have a lead-time of a decade or two before the projected impact.

New submitter catmar68 writes: CERN proposes "space elevator" accelerator to answer this fundamental question: "Do antimatter apples fall up?" From the press release: The true question, they say, is whether antimatter apples fall down differently. If a difference were spotted, it would spell the end of "CPT invariance" -- a principle that has underpinned every theory of physics since the invention of quantum mechanics. "The Standard Model of particle physics has been very successful, but it can't explain the 95% of the universe which is 'dark', and neither Einstein nor any physicist since has been able to cook up a working theory of quantum gravity," says theorist Flora Oilp. "It's time to challenge its most fundamental principle head-on." The way forward, according to Oilp and her colleagues, is to build a vertical accelerator that will put gravity to the test directly. Every previous particle accelerator has been horizontal. A combination of high speeds and frequent course corrections using focusing magnets has always meant that the effect of gravity can be neglected. But by utilising a range of new, revolutionary techniques, including accelerating particles upwards inside a vacuum vessel, and timing how long they take to fall back down to Earth, physicists can study the elusive fourth force directly. Furthermore, by comparing results with protons and antiprotons, they can watch for signs of "CPT violation." Such behaviour cannot be explained using conventional theories, which rely on this principle to ensure the conservation of probability.

The accelerator would be built in two stages. Stage one proposes a 500 m vertical accelerator, starting from the base of the LHC shafts. An exciting collaboration with NASA may come to fruition by utilising detectors on the International Space Station (ISS) to detect beams of particles fired by the accelerator every time the ISS is overhead. This "reverse cosmic-ray" experiment would allow the measurement of Earth's gravity on particle trajectories at unprecedented levels. Stage one will seek to match the roughly 1% precision on measurements of the gravitational constant "g," which is currently being targeted in parallel by experiments with antihydrogen at the Laboratory's Antimatter Factory. This moderate build will also allow engineers and physicists to understand the intricacies of running a vertical accelerator in preparation for stage two -- the space elevator. "If built, however, this advanced particle accelerator would nevertheless be three times taller than the Burj Khalifa in Dubai, which has been the tallest structure in the world since 2009."

The Crew Dragon capsule poised to fly four civilian astronauts to space this year is getting an upgrade: a glass dome will be added at the top to give space tourists a 360-degree view of the cosmos. MSN reports: The glass dome-shaped window replaces Crew Dragon's docking adapter at its nose since the spacecraft won't be docking to the International Space Station. It's similar to the famed cupola aboard the International Space Station, but Crew Dragon's appears to be an uninterrupted sheet of glass, with no support structures dividing the window's view. Crew Dragon's protective aerodynamic shell that shields the hatch door area during launch will pop open to expose the glass dome once the craft is safely in orbit. Based on the rendering SpaceX tweeted, the cupola would fit at least one crew member from the chest up, revealing panoramic views of space.

NASA, which certified Crew Dragon for astronaut flights last year, said it doesn't plan to use the cupola version of Crew Dragon for NASA astronaut missions and that the window's installation doesn't require NASA safety approval. "We've done all the engineering work, we continue to go through all the analysis and testing and qualification to ensure everything's safe, and that it doesn't preclude any use of this spacecraft for other missions," Benji Reed, SpaceX's director of Crew Dragon mission management, said during a press conference on Tuesday.

The US space agency says it expects now to fly the first helicopter on Mars in early April. From a report: The little chopper was carried to the Red Planet by the Perseverance rover, which made its dramatic landing in Jezero Crater just over a month ago. Called Ingenuity, the 1.8kg, twin-rotor aircraft will attempt a series of short hops in Mars' rarefied air. If successful, it would represent something of a "Wright Brothers moment", says Nasa. This is a reference of course to Orville and Wilbur Wright, who in 1903 conducted the historic first heavier-than-air, powered aircraft flight here on Earth. And to mark the connection, the agency revealed that a postage stamp-sized piece of fabric from a wing of the brothers' plane has been taped to Ingenuity.

At the moment, the chopper is still attached to Perseverance, to its belly. A protective covering was released at the weekend and in the coming days the craft will be lowered to the ground. Engineers have identified a 10m by 10m area in Jezero that they're calling the "airfield". This is at one end of a 90m "flight zone", inside which perhaps five sorties will be performed. Perseverance will endeavour to record everything on camera. "We are going to do our very best to capture Ingenuity in flight," said Nasa engineer Farah Alibay. "We're going to be taking images, we're hoping to take video." This will be challenging, she cautioned. Both rover and helicopter function autonomously and carry separate clocks. The timing devices will need to be in sync for the photography to catch the action.

It's been almost half a century since the three astronauts on board the Skylab 4 space mission famously fell out with mission control. Soon afterwards, reports began to circulate that they went on strike. But Ed Gibson, the only one of the crew still alive, says the idea that they stopped work is a myth. From a report: Bill Pogue got sick soon after the three astronauts arrived at the space station. It came as a surprise because Bill had been nicknamed "Iron Belly" during training at the Johnson Space Center in Houston, Texas. He could endlessly tolerate sitting in a rapidly rotating chair while moving his head backwards and forwards and side to side, without being sick. But this was the first time the three men had been in space and evidently resistance to motion sickness back on Earth didn't mean much up there.

Commander Jerry Carr suggested Bill eat a can of tomatoes to settle his stomach. Ed Gibson was sitting between the two men, and remembers the can floating past from left to right before his eyes. "Then I remember some bad noises coming from Bill, and a barf bag floating back from right to left," he says. "We felt discouraged because we knew we had so much work to do -- that's when we made our first mistake." Ed is 84 now and the Skylab 4 mission began in November 1973 but time hasn't dulled his most vivid memories -- the Earth from space, the blazing corona of the sun and the silence of a spacewalk. He's the last one of the astronauts able to share the story, because Jerry Carr and Bill Pogue have both died -- Carr last summer and Pogue in 2014. The Skylab space station was a research platform in orbit where astronauts helped scientists to study the human body's response to space flight, carried out experiments and made observations of the Sun and Earth. Skylab 4 was the final mission and as a result it had a long list of tasks to fulfil. The 84-day mission -- the longest ever at that point -- was on a tight schedule. Nasa was very concerned about someone getting sick, which would have meant losing precious time.

Nasa accepts that mission planners had not given the crew the typical period of adjustment to acclimatise to working weightlessly in orbit and had packed their schedules with large amounts of work. The number of spacewalks was also doubled, to four, to observe a newly discovered comet, Kohoutek. So the astronauts were already under pressure when they made their first bad decision. "We wanted to get organised before starting a big flurry with the ground so we decided to delay telling them about Bill being sick," says Ed. But they had forgotten that everything they said on board was being recorded, and that mission control was listening in. It wasn't long before the voice of Astronaut Office chief Alan Shepard came crackling over the radio from down in mission control, an exchange also broadcast to the public. "He got on the line and read us the riot act for not telling them immediately," says Ed. "Al was OK, we just didn't like being chewed out in front of the whole world."

"A pallet of batteries was released from the International Space Station last week, becoming the heaviest single piece of junk ever jettisoned from the station," reports UPI: Mission controllers in Houston commanded the Canadarm2 robotic arm to release an external pallet loaded with the 2.9 tons of nickel-hydrogen batteries into Earth's orbit Thursday morning. "It is safely moving away from the station and will orbit Earth between two to four years before burning up harmlessly in the atmosphere," NASA said in a statement.
Gizmodo shares a photo of the pallet orbiting 265 miles (427 km) above Chile. And they add that this chain of events starte in 2011 when NASA decided to switch the Space Station from nickel-hydrogen batteries to lithium-ion batteries. This effort required four supply missions from the Japanese H-II Transfer Vehicle (HTV) cargo spacecraft, 13 different astronauts, and 14 spacewalks, in which 48 nickel-hydrogen batteries were replaced by 24 lithium-ion batteries...

"It used to be that it wasn't a big deal to toss stuff from ISS because very few satellites were below it [at altitudes below 250 miles (400 km)], " Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, explained in an email. "That's not so true any more with a bunch of cubesats and with recently launched Starlinks during orbit raising. So I have concerns."

To which he added: "I don't immediately see what else they could have done except fly a whole extra HTV mission just to get rid of it."

According to the European Space Agency, around 34,000 objects larger than 3.9 inches (10 cm) are currently in orbit around Earth, in addition to millions of tinier objects, such as tools and bits of spacecraft. The volume of objects in space, both functional and non-functional, is steadily increasing, prompting concerns of potential collisions and even more orbital debris.
A NASA representative told Gizmodo their ballistics officers "indicate no threat" of the pallet smashing into other space objects, but added "this item, like all, will be tracked by U.S. Space Command."

President Joe Biden is expected to nominate former Sen. Bill Nelson of Florida to lead NASA, settling on a longtime booster of the space program to lead the agency's return to the moon, POLITICO reported Thursday, citing sources. From the report: If confirmed by the Senate, Nelson would lead the space agency as it partners with the new crop of private space companies to establish a long-term presence on the lunar surface in preparation for sending astronauts to Mars. A Senate staffer and a second source familiar with the decision told POLITICO that the administration has picked Nelson, and that the announcement will come on Friday. Both sources spoke on background because they were not authorized to speak ahead of the formal announcement. Nelson, 78, who himself spent six days in orbit when he flew to space in 1986 aboard the Space Shuttle Columbia, served as the top Democrat on the Senate Commerce, Science and Transportation Committee during his 18 years in Congress, where he was instrumental in establishing many of NASA's current priorities.

AmiMoJo shares a report from ScienceAlert: The menagerie of bacterial and fungal species living among us is ever growing -- and this is no exception in low-gravity environments, such as the International Space Station (ISS). Researchers from the United States and India working with NASA have now discovered four strains of bacteria living in different places in the ISS -- three of which were, until now, completely unknown to science.

Three of the four strains were isolated back in 2015 and 2016 -- one was found on an overhead panel of the ISS research stations, the second was found in the Cupola, the third was found on the surface of the dining table; the fourth was found in an old HEPA filter returned to Earth in 2011. All four of the strains belong to a family of bacteria found in soil and freshwater; they are involved in nitrogen fixation, plant growth, and can help stop plant pathogens. Basically, good bacteria to have around if you're growing things. The research has been published in Frontiers in Microbiology.

NASA is counting down to what should be the final major test of the massive rocket it is building to put the first woman and the next man on the moon. From a report: More than 700,000 gallons of supercold propellant will fill up the tanks of the 212-foot tall core stage so that it can fire its four engines without actually blasting off. The goal is to simulate what will happen during its first launch, a mission to send a capsule with no crew around the moon and back. That lunar mission is currently targeted for November, says NASA's acting administrator Steve Jurczyk, who notes that this rocket "is going to be the most powerful rocket ever developed." The window for the rocket test opens on Thursday, March 18, at 3 pm EDT, and the core stage of the rocket is set up at NASA's Stennis Space Center in Mississippi. In a firing test earlier this year, one of the rocket's engines had a failure that forced an early shutdown after only 67 seconds.

"We can understand exactly what happened in the first test and what cut it short," says Jurczyk, who explains that one test parameter had been set too narrowly and that's now been fixed. "Start up on the first test went really well, and so we're reasonably confident we're going to have a good test this week." The test should last around eight minutes, to simulate the entire flight profile of this rocket stage, he explains, but the minimum of what they'd like to see is around 4 minutes. If all goes well, the rocket will move on to Kennedy Space Center in Florida, where the rest of the launch hardware is already waiting. Under the Trump administration, the agency had been aiming to get boots on the lunar surface by 2024, which would have been in a second term if the former president had been re-elected. That deadline was a goal that most in the space community felt was unrealistic. These days, NASA admits that there's no way to get people to the moon that quickly, given the recent appropriations given by Congress.

Oceans' worth of water may remain buried in the crust of Mars, and not lost to space as previously long thought, a new study finds. Space.com reports: Data from NASA's MAVEN (Mars Atmosphere and Volatile EvolutioN) mission and the European Space Agency's Mars Express orbiter revealed that at the rate water disappears from the Red Planet's atmosphere, Mars would have lost a global ocean of water only about 10 to 82 feet (3 to 25 m) deep over the course of 4.5 billion years. Now scientists find that much of the water Mars once had may remain hidden in the crust of the Red Planet, locked away in the crystal structures of rocks beneath the Martian surface. They detailed their findings online March 16 in the journal Science and at the Lunar Planetary Science Conference.

In the new study, the scientists found chemical reactions may have led between 30% to 99% of the water that Mars initially had to get locked into minerals and buried in the planet's crust. Any remaining water was then lost to space, explaining the hydrogen-to-deuterium ratios seen on Mars. All in all, the researchers suggested Mars lost 40% to 95% of its water during its Noachian period about 4.1 billion to 3.7 billion years ago. Their model suggested the amount of water on the Red Planet reached its current levels by about 3 billion years ago.

New submitter byennie writes: A new airless bicycle tire called "METL" was introduced today by The SMART Tire Company. The tire is made from shape memory alloys (SMAs) and was originally designed for Mars rover missions (it's headed to Mars in 2026 as part of the Fetch rover). The structural tire claims to be flat-free and high performance, leaning on the unique properties of SMAs developed at NASA for future heavy vehicles in space. According to the company, "the shape memory alloy tire is made from advanced, lightweight materials known as NiTinol+, creating a tire that is elastic like rubber yet strong like titanium, exhibiting perfect shape memory without ever going flat."

The Verge reports: A SpaceX Falcon 9 rocket launched the latest batch of 60 Starlink satellites into orbit Sunday, and returned to Earth successfully, landing on its Of Course I Still Love You drone ship in the Atlantic Ocean, the company announced. Sunday's mission marked a record ninth flight and landing for this Falcon 9 booster, SpaceX said...

Sunday's launch from NASA's Kennedy Space Center was the second in the past few days for SpaceX, which sent another of its Falcon 9 rockets skyward from Cape Canaveral Space Force Station on Thursday. That launch also brought 60 satellites into orbit.
Sharing a video about the mission, CNET calls it "a new standard for rocket recycling." The first stage that boosted the satellites is a veteran of five previous Starlink missions, Crew Dragon's first demonstration flight, a SiriusXM satellite launch and a Canadian Space Agency satellite mission. The fairing, or nose cone, also previously flew on the Transporter-1 ride-share mission.

Russia and China have signed an agreement to build and work on an "International Scientific Lunar Station" orbiting the Moon, the countries' space agencies announced Tuesday. From a report: The space powers had been in talks for months as Russia mulled over whether it would participate in NASA's Gateway program, a rival lunar space station to be built by a coalition of other countries in the next decade. The International Scientific Lunar Station that Russia and China will work on is "a complex of experimental research facilities created on the surface and/or in the orbit of the Moon," Roscosmos said in a statement. It will be designed to support a variety of research experiments "with the possibility of long-term unmanned operation with the prospect of a human presence on the moon," the statement said.

Like NASA, China has been courting international support for its own plans to put infrastructure on the Moon. It's also sent several robotic Chang'e missions to the Moon, including the first landing on the Moon's far side and a swift sample retrieval mission in December. The lunar space station agreement, signed virtually between China's space chief Zhang Kejian and Russia's space chief Dmitry Rogozin, marks the latest development in Beijing's efforts to explore the Moon alongside rivals like NASA, which is barred from working with China under a law passed by Congress in 2011.

Long-time Slashdot reader Nkwe shares an article from NPR: His job was to sign and submit an official form. Sign the form, he believed, and he'd risk the lives of the seven astronauts set to board the spacecraft the next morning. Refuse to sign, and he'd risk his job, his career, and the good life he'd built for his wife and four children.

"And I made the smartest decision I ever made in my lifetime," McDonald told me. "I refused to sign it. I just thought we were taking risks we shouldn't be taking...."

Now, 35 years after Challenger, McDonald's family reports that he died Saturday in Ogden, Utah, after suffering a fall and brain damage. He was 83 years old.

"There are two ways in which [McDonald's] actions were heroic," recalls Mark Maier, who directs a leadership program at Chapman University and produced a documentary about the Challenger launch decision. One was on the night before the launch, refusing to sign off on the launch authorization and continuing to argue against it," Maier says. "And then afterwards in the aftermath, exposing the cover-up that NASA was engaged in...."

He later co-authored one of the most definitive accounts of the Challenger disaster: Truth, Lies, and O-Rings — Inside the Space Shuttle Challenger Disaster. In retirement, McDonald became a fierce advocate of ethical decision-making and spoke to hundreds of engineering students, engineers and managers.

Since landing on Mars on February 18, NASA's Perseverance rover has sent back some amazing images from around its landing site, Jezero Crater, a 30-mile wide impact depression just north of the Red Planet's equator. BBC shares a selection of the pictures sent from the mission, "as Perseverance hunts for signs of past microbial life, seeks to characterize the planet's geology and past climate, and collects Martian rock." You can view the images here.

Rocket Lab has unveiled plans for a larger rocket that can carry bigger payloads than its current reusable trooper, the Electron. It's called the Neutron and will be capable of carrying 8 metric tons to low-Earth orbit compared to the Electron's 660 lbs capacity. Engadget reports: The Neutron will also have a fully reusable first stage that can land on an ocean platform, in the same vein as SpaceX's Falcon 9 booster. Rocket Lab is looking to fast-track the rocket's first flight to 2024 by using the existing launch pad at Virginia's Mid-Atlantic Regional Spaceport located at the NASA Wallops Flight Facility. It's also scouting sites across the US to build a new factory where the Neutron will be assembled at scale.

The new rocket is designed with an eye to the future of mega-satellite constellations. Its larger payload means it can take multiple small satellites in batches to specific orbital planes, creating a "a more targeted approach to building out" the massive projects, said Peter Beck, Rocket Lab founder and CEO. Demand for the constellations is growing, with the satellite networks enabling better navigation and providing communications in rural areas back here on Earth. The Neutron's lift capacity also means it should be able to transport 98 percent of all satellites forecast to launch through 2029.

"Mars, Shmars; this voyager is looking forward to a submarine ride under the icebergs on Saturn's strange moon," says the New York Times, introducing a piece by cosmic affairs correspondent Dennis Overbye: What could be more exciting than flying a helicopter over the deserts of Mars? How about playing Captain Nemo on Saturn's large, foggy moon Titan — plumbing the depths of a methane ocean, dodging hydrocarbon icebergs and exploring an ancient, frigid shoreline of organic goo a billion miles from the sun? Those are the visions that danced through my head recently...diverted to the farther reaches of the solar system by the news that Kraken Mare, an ocean of methane on Titan, had recently been gauged for depth and probably went at least 1,000 feet down. That is as deep as nuclear submarines will admit to going. The news rekindled my dreams of what I think would be the most romantic of space missions: a voyage on, and ultimately even under, the oceans of Titan...

NASA recently announced that it would launch a drone called Dragonfly to the Saturnian moon in 2026. Proposals have also circulated for an orbiter, a floating probe that could splash down in a lake, even a robotic submarine. "The Titan submarine is still going," said Dr. Valerio Poggiali, research associate at the Cornell Center for Astrophysics and Planetary Science, in an email — although it is unlikely to happen before Titan's next summer, around 2047. By then, he said, there will be more ambient light and the submarine conceivably could communicate on a direct line to Earth with no need of an orbiting radio relay.

Titan is the weirdest place in the solar system, in some regards, and also the world most like our own. Like Earth, it has a thick atmosphere of mostly nitrogen (the only moon that has much of an atmosphere at all), and like Earth, it has weather, rain, rivers and seas. But on this world, when it rains, it rains gasoline. Hydrocarbon material drifts down like snow and is shaped into dunes by nitrogen winds. Rivers have carved canyons through mountains of frozen soot, and layers of ice float on subsurface oceans of ammonia. The prevailing surface temperature is minus 290 degrees Fahrenheit. A chemical sludge that optimistic astronomers call "prebiotic" creeps along under an oppressive brown sky. Besides Earth, Titan is the only world in the universe that is known to harbor liquid on its surface — with everything that could imply.