Enjoy this sneak-preview from the Heat issue of Popular Science, live on July 13. Current subscribers can access digital editions here, and new subscribers can click here to join in.

Jörn Helbert was standing outside a stranger’s apartment in the north end of Berlin with a bouquet of yellow roses. It was June 2020, and the woman behind the door was in mandatory quarantine. She had just moved to Germany from the United States, and as a favor to Helbert, a fellow planetary scientist, she was acting as a courier, bringing rocks far too precious to be put in the care of international postal systems hopelessly backlogged because of the pandemic. Already one shipping snafu had sent the package to a nail salon in Tucson and nearly lost it. Helbert was familiar with the kind of questioning you might run into when carrying geologic samples through German customs, so the flowers were a gift for her trouble.

The handoff had involved so much effort and intrigue that he felt as if the parcel should be in a suitcase that got handcuffed to his wrist. Instead, Helbert was amused to see a rumpled plastic Walgreens bag left outside for contactless pickup. It held 30 disks made of various rocks analogous to those that might be found on Venus. They had been painstakingly collected and analyzed by Darby Dyar, an astronomy professor at Mount Holyoke College in Massachusetts.

Helbert, Dyar, and a team of colleagues were in the last stages of pitching NASA on a mission called VERITAS, which would send a satellite to map Venus at higher resolution than ever before. Despite the pandemic, their deadlines hadn’t budged. NASA selects low-cost (around $ 500 million) projects through a program called Discovery only every few years. The team was desperate to get the rock disks into Helbert’s lab at the German Aerospace Center, where he was calibrating an instrument for the VERITAS spacecraft that could determine what sorts of rocks make up Venus’ geological formations; getting a better sense of these would help write the planet’s history. Granite could show us where there were oceans. Basalt could lead us to active volcanoes. Stitching the features together could show us the steps that turned the planet into an uninhabitable inferno.

If you imagine that our solar system is a cul-de-sac where Earth is our cozy home and Mars is the empty lot down the street where developers pitch a shiny future, then Venus is the haunted house a few doors down, camouflaged by an overgrown yard and drawn curtains. It’s similar to Earth in size, density, mass, composition, and gravitational pull, but at its surface, it has lead-melting temperatures of more than 850°F and air pressure equivalent to standing under half a mile of ocean water. Its magnetic field is too weak to protect it from the solar wind, it spins backward, and it has a permanent layer of heat-trapping clouds that veil its face from view.

The best topographic radar maps we have were produced in the 1990s, and they’re quite coarse compared to our charts of Earth and Mars. We know Venus’ surface has mountains, valleys, volcanoes, lava fields, and bizarre geological goodies, but among its many mysteries, scientists still don’t even really know what kind of rocks might reside there.

[Related: What NASA’s twin Venus missions hope to uncover]

Venusophiles say it’s embarrassing that we haven’t gotten to know our neighbor better. Magellan, NASA’s last expedition there, left Earth in 1989. Since then, the space agency has launched 14 missions to Mars while researchers submitted about 30 Venus proposals to no avail. VERITAS was already in that ignominious club of the unchosen; earlier iterations had been put forward for more than a decade. During the last round, in 2017, VERITAS and DAVINCI, a very different Venus project aimed at sampling the planet’s noxious atmosphere, had been part of a five-team Discovery shortlist, but hadn’t made the final cut.

After that disappointment, David Grinspoon, one of the DAVINCI scientists, wrote an essay titled “Not Venus Again,” lamenting that he and his colleagues were like long-suffering Cubs fans but if the Cubs had made it to the World Series and lost.

In the spring of 2021, both teams were back at the plate, anxiously awaiting NASA headquarters to call with their Discovery decisions. “I’ve really put my heart and soul into this particular mission, so for me, it is now or never,” says VERITAS principal investigator Sue Smrekar, a geophysicist at NASA’s Jet Propulsion Laboratory in California. “I can’t imagine investing this intense effort again into getting a mission selected.”

Other countries are planning Venus missions, because there are good reasons to go. As scientists have studied solar systems beyond our own with instruments like the recently retired Kepler Space Telescope, they’ve found dozens of exoplanets with Earth-like properties. That prospect has reawakened the question that has confounded astronomers and philosophers alike for millennia. Are we alone? Except here’s the thing: We have a rocky twin world next door that looks nothing like ours. “I want to understand why Earth is the place where life can exist, and that’s what Venus can tell us,” says Martha Gilmore, a planetary geologist who is on both teams. “I think it’s of the highest priority for understanding how we got to be here.”

Venus sometimes appears as a twilight star that chases down the sun, other times as a morning star that rises at dawn. Early revelations about the planet gave just enough license for wild speculation about what—and who—might be living there. In 1761, Russian physicist Mikhail Lomonosov observed Venus transiting in front of the sun like a roving freckle, a rare phenomenon that allowed astronomers to estimate its diameter. Lomonosov noticed a strange fuzziness around its edges. That haze, he concluded, was a thick atmosphere. Because clouds on Earth were made of water, it stood to reason that Venus should be a very steamy and swampy place.

In the late 18th century, astronomers also developed a theory that the orbs in our solar system got progressively older the farther from the sun they were. By the late 19th, some imagined Mars, the fourth planet, to be covered in ruins of abandoned canals dug by long-dead thirsty beings. Meanwhile, Venus, the second, enjoyed a reputation as our more primordial twin, full of landscapes that resembled our world in the Carboniferous Period 350 million years ago, when fern forests grew, freakish sharks dominated the seas, and four-limbed creatures were just beginning to stretch out across the land. Perhaps old myths that associated Venus with fertility goddesses contributed to this Edenic image. The Victorian poet Alfred, Lord Tennyson gave it “never fading flowers.” Ray Bradbury, in one short story, pictured the planet more grimly as covered in a sickly white jungle with “cheese­colored leaves,” soil like “wet Camembert” and ceaseless rainfall that feels like a thousand hands touching you when you don’t want to be touched.

Lush visions of Venus dried up as new evidence trickled in. One especially damning sign came in 1956, when a team at the Naval Research Laboratory in Washington, D.C., pointed the 50-foot dish of its radio telescope at the planet. They found it emitted the amount of radiation they would expect from an object hotter than 600°F. NASA’s Mariner 2 spacecraft—the first-ever successful planetary probe to leave Earth—confirmed the hot atmosphere during a flyby in 1962.

It was during this decade that astronomer Carl Sagan made a name for himself proposing that a greenhouse effect was at work on Venus, with poison gases in the clouds locking heat in. In October 1967, the Soviets sent their Venera 4 probe there, this being the first time a spacecraft entered another planet’s atmosphere. It beamed back disconcerting data: The air was much denser than expected and was made up of 95 percent carbon dioxide with negligible amounts of oxygen and water vapor. So crushing was this result that in 1968, science fiction authors Brian Aldiss and Harry Harrison put together a mournful anthology called Farewell, Fantastic Venus,gathering suddenly unscientific essays and stories from researchers and sci-fi writers that had been set on the “no-longer magical” world.

Although astronauts lost any hope of planting their boots on Venus, exploration continued. In 1975, Venera 9’s descent vehicle delivered the first photograph of the surface, a 180-degree panorama showing a desolate field strewn with shattered rocks and boulders. NASA’s 1978 Pioneer Venus mission produced the first crude radar maps. But in the decade that followed, NASA launched no planetary science missions. President Ronald Reagan, who took office in 1981, helmed this dark age, focusing the agency’s efforts on near-Earth orbits reachable by the space shuttle.

One casualty was the planned Venus-mapping VOIR (Venus Orbiting Imaging Radar) spacecraft. When the news came in 1982, Dyar, now deputy principal investigator of VERITAS, was a graduate student in plan­etary science at MIT. She arrived that day to find classmates openly crying. Eventually the research community was able to patch together a simpler, cheaper version, which launched in 1989 as Magellan, an orbiting spacecraft that mapped what was beneath Venus’ impenetrable cloud layer by bouncing radar waves off the planet’s surface.

In the early 1990s, then–NASA administrator Dan Goldin established the Discovery program to fulfill his “faster, cheaper, and better” mandate, emphasizing the use of ready-made commercial hardware and software to get small missions off the ground. The second project to launch, in 1996, was Pathfinder, which included a Mars lander and the first-ever rover, a wagon­size vehicle named Sojourner. It was a huge success and drummed up public support for exploration of the red planet. NASA approved projects with increasingly big budgets: the Mars Odyssey orbiter (2001), the rovers Spirit and Opportunity (2003), the still-operating Mars Reconnaissance Orbiter (2005). Those undertakings paved the way for Curiosity, InSight, and now Perseverance. Since the 1990s, the guiding principle for these efforts has been to “follow the water,” looking for conditions that could once have supported life—but undoubtedly driven by the tantalizing prospect of future human exploration.

With so much money going into Mars, that’s where planetary scientists go. Curiosity alone has had nearly 500 working on its 10 instruments, and untold numbers of grad students have cut their teeth on its data. Success begets success in the eyes of the public too. New Mars rovers aren’t presented like $ 2.5 billion pieces of hardware but lovable extraterrestrial road-trippers who narrate their journeys on social media and share photos along the way. NASA knows how to sell Mars to taxpayers. It’s less clear how to market Venus, hostile to human eyes and rovers alike.

Throughout the past couple of decades, interest in places beyond Mars hasn’t entirely disappeared. NASA’s next flagship mission, the $ 4.25 billion Europa Clipper, will launch in 2024 to spend about six years traveling to Jupiter to study the ice shell and ocean of the planet’s sixth-farthest moon. But Venus has been a glaring blind spot, especially considering it’s so close to Earth. (A spacecraft takes only about four months to get there.) Although NASA hasn’t dedicated a line of funding to studying Venus since the 1990s, a passionate research effort has persisted. Scientists are still reanalyzing data from Magellan and even the Pioneer and Venera missions. They’re also looking at info from the European Space Agency’s Venus Express and the Japanese Akatsuki climate orbiter—the only two such undertakings since Magellan.

Sue Smrekar, the VERITAS leader, was a postdoc at MIT when Magellan sent the first results of its radar mapping to JPL. The whole team was assembled, along with many guest investigators from around the world, to look at what she recalls as the “familiar yet alien images.” She thought it was the closest she would come to “setting foot on another world.” Here were topographic surveys of geologic features found nowhere else, such as tesserae, strange upland regions with such chaotic-looking ripples that researchers named them with the Greek word for mosaic tiles. Some scientists think the formations could be the equivalent of Earth’s continents; others believe they might be more like the scum on top of a pond of hardened magma.

Magellan also documented a small number of meteorite craters, most of which were quite pristine, suggesting that Venus’ current surface is relatively fresh, around 500 million years old. Many think this overhaul happened in a planetwide volcanic event, perhaps on par with the end-Permian extinction that wiped out most species on our Pale Blue Dot. Volcanism on Earth is linked to plate tectonics; however, scientists have yet to find evidence of Venus’ crust shifting, so what drives its eruptive properties remains opaque.

The data left gaps Venusophiles were determined to fill in. Magellan’s image resolution was around 100–250 meters across each pixel. VERITAS (short for Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) would improve that by an order of magnitude. Perhaps more impressively, it would boost the topographic resolution by two orders of magnitude. In its pitch to NASA, the VERITAS team showed how Hawaii’s Big Island would look in Magellan’s view: like an unintelligible collection of pixels. The VERITAS view brought the volcanic island’s ridges and valleys and the peak of Mauna Kea into sharp relief.

“I often compare where we are with Venus to where we were with Mars in the ’80s,” says Paul Byrne, a planetary geologist at North Carolina State University in Raleigh who’s due to take up a new post soon at Washington University. He’s not part of either mission but has advocated for more research on the planet in general. He leads the Venus panel of the Planetary Science Decadal Survey, which helps set the field’s priorities for the next 10 years. “We had global image coverage of Mars, but it was relatively coarse. And it was when we started to fly more capable instruments there we started seeing stuff that we could never have dreamed we’d see in terms of the detail. We don’t have that for Venus yet.”

[Related: What does the surface of Venus look like?]

VERITAS, which would launch around 2028, would also glean new data about the composition of Venus’ geologic formations using spectroscopy, an imaging technique to identify matter based on how it absorbs and reflects light. Because Venus’ thick clouds block most light, Dyar, Helbert, and their colleagues had to invent a whole new way to interpret the data that can squeeze through the narrow wavelength range that can penetrate the cover.

Helbert created a Venus-simulating chamber in his lab that would heat Dyar’s rocks to ungodly temperatures to test a prototype of the Venus Emissivity Mapper, or VEM, one of the instruments proposed for VERITAS. COVID-19, of course, was the wrench in their international collaboration, especially considering the teams found out only in February 2020 that they were moving to the next level of Discovery program selections. They needed more data from various igneous rocks to expand their calibration of the instrument. During those early confusing months of the pandemic, Dyar sent frantic emails to colleagues across the country asking for samples and soon had a large collection from locations like Pikes Peak in Colorado, Mount St. Helens in Washington, and the Leucite Hills in Wyoming. Some of the samples were the size of softballs and needed to be cut into small disks to fit in the Venus chamber. With her college closed, Dyar appealed to a retired mineral collector who had special saws and grinders in his basement to do the job. In a rendezvous in a Friendly’s parking lot, she received the 30 rock disks that would eventually make their way to Berlin. 

While VERITAS would have its eyes on the ground, DAVINCI+—for Deep Atmosphere of Venus Investigations of Noble Gases, Chemistry and Imaging (the plus sign added for this round of proposals)—is primarily designed to search for clues about the planet’s history in its opaque atmosphere. The concept was born out of a Venus summit in late 2007 and early 2008, but the current principal investigator, Jim Garvin, chief scientist at NASA’s Goddard Space Flight Center in Maryland, has been dreaming of a new expedition since he finished his Ph.D. in the 1980s. The spacecraft would launch around 2029 and drop a parachute-equipped, aeroshell-protected spherical probe that would sail through the cloud cover. Using spectrometers similar to the ones developed for the chemistry lab aboard Curiosity, it would measure inert gases like krypton and xenon (think of them like fossils of the early processes that formed Venus’ atmosphere) as well as hydrogen isotopes, which could determine when and at what rates the planet lost the oceans it is suspected to have had in its early history.

That water-loss data would be hugely important. Michael Way, a physical scientist at NASA’s Goddard Institute for Space Studies in New York, and his colleagues produced models in 2016 suggesting Venus not only had water before Earth did but also was covered in a shallow ocean for some 3 billion years. Those findings have energized researchers and revived the image of a wet world, at least in its past. “You put that 3 billion years of water on Venus next to the 300 million years that Mars had water and you realize that if we’ve been looking for signs of life somewhere else in our own solar system, maybe we’ve been barking up the wrong tree,” says Dyar. 

The DAVINCI+ team also proposes to put a camera on its descent vehicle to capture views of the surface far better than the Venera 9 images that hooked Garvin when he was a student. He’s convinced his spherical probe can see mountains at scales not possible from orbit. To prove it, he hired a UH-1 (Huey) helicopter test crew in August 2016 to take him for a series of daredevil rides over a quarry in Maryland. As the aircraft plunged toward the ground, trying to mimic the path of the descent vehicle, he hung out the window taking pictures of the rocks below. This past winter the team heated a full-scale prototype in the lab to make sure it could operate in the atmosphere long enough to send readings home.

Coloring in our image of Venus’ long-gone seas could help answer the Big Question. In the 260 years since Lomonosov watched the planet’s transit, scientists have developed telescopes so sophisticated they can observe the transit of faint planets in systems thousands of light-years away. Based on their size, their motion, and the wavelengths of light they emit, astronomers can estimate the conditions of the orbs. Some 60 are considered potentially habitable, meaning they appear to have the right parameters to sustain liquid oceans. But by those same parameters, if we were observing our own solar system from afar, we might think Venus should be Earth-like too. “If you can’t understand Venus, which is our closest Earth-like neighbor, what chance do you have of believing anything some astrophysicist tells us about exoplanets?” says planetary scientist Sanjay Limaye of the University of Wisconsin–Madison.

Limaye is part of a contingent of Venus researchers interested in finding out whether its cloud layer could still host microbial life. In 2020, investigators reported in the journal Nature Astronomy seeing signatures of phosphine—a chemical known thus far only to come from biological sources—in the atmosphere. Though claims about the possible discovery didn’t pan out, the news helped to spotlight the planet as an overlooked astrobiology target.

The Indian Space Research Organization plans to fly its own radar-mapping orbiter at the end of 2024—and it’s not the only foreign space agency actively pursuing a Venus trip. The ESA intends to launch a satellite called EnVision in the early 2030s to look at recent geological activity. And Russia is considering a mission called Venera D that would sniff for signals of life. In 2016 NASA launched its HOTTech program to fund research into hardware that could survive at hellish temperatures for at least a couple of months; with such tech, a Venus lander or rover could be a possibility.

What the Venus research community needs most is more data. Lauren Jozwiak, a VERITAS volcanologist at Johns Hopkins University who got her Ph.D. in 2016, says she was told to look elsewhere in her studies since there were few prospects for Venus. An influx of new data, though, will feed the next generation. “There is so much that we don’t know about Venus,” she says.

[Related: What jostling in Venus’ crust could reveal about Earth’s early geology]

In the early hours of June 2, 2021, Smrekar and Dyar were sitting in their respective kitchens on opposite sides of the country, texting back and forth. Neither had slept much. This was the morning they knew they’d find out which Discovery missions NASA had greenlit. Around 5:30 a.m. Pacific Daylight Time, Smrekar got the call: VERITAS had been approved.

“It is an indescribable feeling to work toward something for 10 long years with heart and soul and finally have it come to fruition,” Dyar says. She spent the day wandering around in shock until she could pop corks with her colleagues in a virtual fete. Smrekar was ecstatic. “I don’t plan to stop celebrating for a while,” she says.

When the agency phoned Garvin that same morning, he nearly fell off his chair. DAVINCI+ would be going to space too. The next few days were a blur—his team buzzing. Both missions had beaten out their competitors, spacecraft proposed to explore Jupiter’s moon Io and Neptune’s moon Triton. After a 30-year drought of new NASA missions to Venus, two will rocket there within the decade, the product of countless hours of research and testing, rock fetching, helicopter riding—and relentless optimism.

“We’ve got this brilliant planet sitting next door with a giant atmosphere and a fascinating crust and a history that somehow didn’t end up like our own planet’s,” says Garvin. “To look back in time at what that world was like—probably Earth-like and maybe even better—is an opportunity for the people of planet Earth at this point. Maybe 30 years ago we weren’t ready. But now we are.”

We hope you liked this sneak-preview from the Heat issue of Popular Science, live on July 13. Current subscribers can access digital editions here, and new subscribers can click here to join in.