Venus

Venus is the second planet from the Sun and the closest in size to Earth, with 95 percent of Earth's diameter and 82 percent of its mass. A carbon dioxide atmosphere roughly 90 times as massive as Earth's traps heat in a runaway greenhouse, holding the surface near 465 °C under 92 bar of pressure, beneath an unbroken deck of concentrated sulfuric acid clouds that hides the ground from view.^[10]

Venus is the brightest natural object in Earth's sky after the Sun and the Moon, and it was the first planet visited by a spacecraft, yet it has spent most of the past three decades ignored. A disputed 2020 claim of phosphine gas in its clouds, along with evidence that the planet may once have had oceans, has pulled attention back. Five missions are now in development, but nothing is working at Venus today: Japan's Akatsuki orbiter stopped responding at the end of April 2024, and its operators ran the termination procedure on September 18, 2025.^[9]

Venus compared with Earth#

Venus is the planet closest to Earth in size, which earned it a reputation as Earth's twin, but the two diverge in nearly every other measurement: Venus has no moon, and its surface is hot enough to melt lead.^[10]

Runaway greenhouse and surface conditions#

Venus's surface is hotter than Mercury's even though Venus orbits nearly twice as far from the Sun, and conditions are remarkably uniform: the massive atmosphere transports heat so efficiently that temperatures barely differ between equator and poles or day and night.^[10] Near the ground, carbon dioxide is compressed into a supercritical fluid, and the gentle winds push against a lander like a slow ocean current. The planet rotates backward once every 243 Earth days, longer than its 225-day year, yet the upper atmosphere super-rotates, with cloud-top winds near 360 km/h circling the planet every four days.^[10]

The greenhouse was probably self-inflicted. As the young Sun brightened, any surface water evaporated; water vapor amplified the warming, ultraviolet light split the molecules, and the hydrogen escaped to space. The evidence survives in the atmosphere's deuterium-to-hydrogen ratio, roughly 100 times Earth's, the signature of a planet that lost a large water inventory.^[11] Without water to lubricate plate tectonics or sustain a carbon cycle, carbon dioxide simply accumulated.

Hydrogen is still leaving. A 2024 modeling study identified the dominant present-day escape route as dissociative recombination of the ion HCO+, a channel earlier work had overlooked, and concluded that it roughly doubles the rate at which Venus loses water. The planet now holds around 100,000 times less water than Earth despite being nearly the same size.^[12]

Clouds and superrotation#

Venus's cloud deck is made of concentrated sulfuric acid droplets, and the band that entry probes are designed to sample runs from about 48 to 60 km above the surface.^[8] Near the 50 km level the temperature falls to somewhere between about 30 °C and 70 °C at roughly Earth-like pressure, which is why proposals for aerial exploration, and for cloud-borne life, concentrate on that layer rather than the ground.^[17]

The atmosphere as a whole turns about 60 times faster than the solid planet beneath it.^[13] Tracking clouds in ultraviolet and infrared images from Akatsuki, a team led by Takeshi Horinouchi showed in 2020 that the superrotation is sustained by thermal tides, waves raised by the difference in solar heating between the day and night sides. Those tides carry angular momentum toward the equator at cloud-top level, while turbulence and other waves push the opposite way at middle and high latitudes.^[13]

One basic property of the clouds is still unexplained. Something in them absorbs strongly in the ultraviolet, producing the dark markings that make cloud tracking possible in the first place, and dozens of candidate substances have been proposed over the past century. A 2024 laboratory study offered two iron-bearing sulfate minerals, rhomboclase and acid ferric sulfate, which are stable under Venusian cloud conditions and reproduce the observed absorption pattern.^[14]

Did Venus once have oceans?#

Whether Venus was ever habitable is genuinely unsettled. Climate modeling by scientists at NASA's Goddard Institute for Space Studies in 2016 found that with its slow rotation and a shallow ocean, early Venus could have kept moderate surface temperatures for as long as two billion years, with thick daytime clouds shading the surface.^[1] Emissivity data from orbit hint that the highland tesserae may be granite-like rock, which on Earth forms in the presence of water.^[16] A 2021 modeling study countered that water may never have condensed on Venus at all, with rain evaporating before reaching the hot early surface, and Earth escaping the same fate only because the faint young Sun gave it time to cool.^[2] The lack of leftover oxygen in today's atmosphere also argues against a late, rapid ocean loss.

A 2024 study approached the question from atmospheric chemistry rather than climate physics. Researchers at the University of Cambridge calculated how fast water, carbon dioxide and carbonyl sulfide break down in the atmosphere and what volcanic gases would be needed to replace them, and found the resupply consistent only with eruptions carrying at most 6 percent water, far drier than comparable terrestrial magmas. On their reading the mantle never held enough water for oceans, and Venus has been inhospitable for its entire history.^[15] Deciding between these histories requires isotopic and geologic ground truth, which is exactly what the next generation of missions is designed to collect.

The phosphine debate#

In September 2020 a team led by Jane Greaves reported phosphine gas at about 20 parts per billion in Venus's cloud deck, based on observations with the James Clerk Maxwell Telescope (JCMT) and the ALMA array. The claim drew attention because on Earth phosphine is produced mainly by anaerobic microbes and industry, and no known Venusian chemistry makes it in such quantities.^[3] Independent groups quickly challenged the result: reanalyses of the ALMA data shrank or erased the signal, and skeptics argued that an overlapping sulfur dioxide line or calibration artifacts could mimic phosphine. The discovery team reprocessed its data and maintained a weaker detection, a few parts per billion averaged over the planet rather than 20, and a long-running JCMT monitoring program has continued to report absorption consistent with phosphine that varies over time.^[3][4]

That program, JCMT-Venus, watches phosphine alongside sulfur dioxide, sulfur monoxide, HCO+ and semi-heavy water to test whether the abundance shifts with time, location, or other atmospheric conditions. Its own summary is that much about the reported phosphine remains undetermined.^[18] Greaves has separately announced a tentative detection of ammonia, another gas with no accepted Venusian source, and in 2025 proposed VERVE, a CubeSat that would travel with EnVision and then separate to map both gases from orbit.^[17]

As of 2026 there is no consensus that phosphine is present, and reviews of the controversy conclude the question must stay open until multiple independent techniques, ideally including measurements made inside the atmosphere, converge.^[3][4] The dispute has nonetheless reshaped the field, reviving serious study of whether Venus's temperate cloud layers, around 50 km up, could host any form of aerial life.

Venera landings and early exploration#

Venus was the proving ground of early planetary flight. NASA's Mariner 2 performed the first successful planetary flyby in December 1962 and confirmed the scorching surface. The Soviet Union then mounted the Venera program, the only campaign ever to operate landers there, and ten of its probes reached the surface and transmitted from it.^[19] Venera 7 achieved the first survivable landing on another planet on December 15, 1970, transmitting for about 23 minutes; Venera 9 returned the first photographs from another planet's surface in October 1975; and Venera 13, on March 1, 1982, sent color panoramas and analyzed a drilled soil sample, enduring 127 minutes in an environment it was designed to survive for half an hour. The twin Vega missions of 1985 added balloons, deployed on June 11 and June 15, that drifted through the temperate cloud layer on the night side and returned data for 46.5 hours each.^[20] No lander has ever lasted longer than about two hours on the surface.

Magellan and the mapped surface#

NASA's Magellan orbiter radar-mapped 98 percent of Venus between 1990 and 1994, revealing tens of thousands of volcanoes, long lava channels, crumpled tessera highlands, and fewer than 1,000 impact craters, implying the surface is only a few hundred million years old.^[21] The counts have since been sharpened. A catalogue published in 2023 identified about 85,000 volcanic edifices in the Magellan images, roughly 99 percent of them less than 5 km across and most too small for earlier surveys to have caught.^[23] The crater database now holds 967 features accepted as impact structures, scattered almost at random, which is what makes the surface read as uniformly young rather than patchily old.^[22] Tessera terrain, the deformed highland material thought to be the oldest surface on the planet, covers about 8 percent of it.^[16]

The European Space Agency's Venus Express orbiter (2006-2014) and JAXA's Akatsuki (2015-2025) studied the atmosphere and its superrotation. Akatsuki went quiet during a spell of low-precision attitude control at the end of April 2024; recovery attempts failed, the spacecraft had long outlived its design life, and JAXA closed the mission on September 18, 2025, leaving the planet unattended.^[9] Europe's Jupiter-bound Juice spacecraft swung past Venus on August 31, 2025 for a gravity assist, but the thermal environment forced its remote sensing instruments off, so it returned no observations of the planet.^[40]

Volcanism and a still-active interior#

Magellan's three-decade-old archive keeps producing evidence that Venus is geologically alive. In 2023, researchers comparing radar images taken eight months apart in 1991 found a vent on the north flank of a shield volcano in the Maat Mons system that had changed shape and grown by roughly half between February and October, the first direct sign of an eruption in progress.^[24] A second study, published in Nature Astronomy in 2024, compared radar passes from 1990 and 1992 and found brightening consistent with fresh lava covering about 30 km² at Sif Mons and about 45 km² in western Niobe Planitia, averaging 3 to 20 m deep. Its authors argued that Venus may be volcanically active on a scale comparable to Earth.^[25]

Interior motion also shows in the gravity field. A 2025 analysis paired Magellan gravity and topography data across 75 coronae, the circular fracture rings that are one of Venus's signature landforms, and found buoyant mantle material beneath 52 of them. Individual coronae record different processes: surface material pushed down into the mantle, dense lithosphere dripping away, and plumes driving volcanism.^[26] A catalogue presented in 2026 had grown to 741 coronae and treats them as the product of several mechanisms rather than one, with the caveat that existing gravity data is too coarse to detect much of the activity that may be there.^[27]

In February 2026 a group at the University of Trento reported the first radar evidence of a lava tube on Venus: a conduit roughly a kilometer wide beneath the shield volcano Nyx Mons, identified from a collapse pit and estimated to extend at least 45 km, with a roof at least 150 m thick and a void at least 375 m deep.^[28] The size estimate depends on simplified assumptions about the tube's geometry, and commentators outside the team have noted that confirming these are skylights into lava tubes would require exploring the openings directly.^[29]

Upcoming missions#

Five missions to Venus are in development as of August 2026, and none has launched: two NASA missions, a European radar orbiter, an Indian orbiter, and a privately funded atmospheric entry probe.

NASA's two Venus missions have survived one cancellation attempt and are facing a second. The administration's fiscal 2026 budget request proposed ending both, but the appropriations act passed in January 2026 restored them, providing 99 million dollars to keep the DAVINCI descent-probe mission moving.^[5][6] The fiscal 2027 request, released in April 2026, goes further: it would cancel DAVINCI and VERITAS, end NASA's contribution to ESA's EnVision, and close the agency's Venus technology line, removing NASA from Venus exploration altogether. No other destination in the solar system is zeroed out that completely in the request.^[30] A budget request is a proposal rather than law, and Congress reversed the equivalent cuts a year earlier, but as of August 2026 the missions have no funding in the administration's plan.

DAVINCI will measure noble gases and the deuterium ratio all the way down and photograph the tesserae up close. Its roughly one-meter probe is designed to be the first to descend through the Venusian atmosphere since the Vega landers of 1985, and sampling the clouds on the way down is the most direct route to settling the phosphine question.^[16][31] The launch is set for the early 2030s and no earlier than 2031.^[31] VERITAS, which will map topography and surface composition globally at resolutions Magellan could not reach, restarted engineering work in October 2024 after a stand-down forced by staffing problems at the Jet Propulsion Laboratory; principal investigator Sue Smrekar has put the target at June 2031 while acknowledging a real possibility of slipping to late 2032.^[32]

ESA's EnVision, adopted in January 2024, is set to launch on an Ariane 6 in November 2031, with backup opportunities in 2032 and 2033. It will spend 15 months cruising and 11 months aerobraking into a quasi-polar orbit between 220 and 510 km, then pair radar imaging and a subsurface sounder with atmosphere-watching spectrometers for a nominal four Earth years.^[7] Thales Alenia Space signed the spacecraft construction contract in January 2025.^[33] The mission's radar, VenSAR, is a NASA contribution, which is what turns the US budget fight into a European problem too.^[34] ESA has said it retains the technical capability to build such instruments in Europe if it has to, while stressing that it is still working with NASA.^[35]

ISRO's Venus Orbiter Mission, also called Shukrayaan, was approved by India's union cabinet on September 18, 2024 at a cost of about 12.4 billion rupees and is aimed at a March 2028 launch. It will study the atmosphere, the surface and subsurface, and the Sun's influence on the atmosphere, and its science goals include a search for phosphine.^[36] China has not approved a Venus orbiter, but a Venus atmosphere sample return sits in the second phase, covering 2028 to 2035, of the long-term space science roadmap that the Chinese Academy of Sciences, CNSA and the human spaceflight office published in October 2024.^[37]

The first of the new wave may still be private. Rocket Lab, working with an MIT science team led by Sara Seager, plans to send a probe of about 20 kg on an Electron-launched Photon cruise stage.^[38] The probe carries a single instrument, an autofluorescing nephelometer, and would get roughly five minutes inside the cloud layer between 48 and 60 km to search droplets for organic molecules.^[8] The schedule has slipped repeatedly, from an original 2023 date to a January 2025 window that was missed, and the team has since been working toward a 2026 launch; the probe had not flown as of early August 2026.^[8][38]

Venus in Earth's sky#

Venus orbits the Sun at an average distance of about 108 million km (0.72 AU), inside Earth's orbit, so it never appears far from the Sun and is seen as a morning or evening object rather than overhead at midnight.^[10] Roughly twice a century it crosses the solar disc as a small black dot. Transits come in pairs eight years apart, separated by gaps of 105.5 and then 121.5 years; the most recent pair fell on June 8, 2004 and June 6, 2012, and the next is due on December 11, 2117.^[39]

References#

1. NASA Climate Modeling Suggests Venus May Have Been Habitable - NASA Goddard Institute for Space Studies.
2. A new Climate Model Suggests That Venus Never had Oceans - Universe Today.
3. Life on Venus? - PMC / National Institutes of Health.
4. Source of phosphine on Venus, an unsolved problem - Frontiers in Astronomy and Space Sciences.
5. NASA's Budget Woes Are Over, For Now - Sky & Telescope.
6. NASA's ambitious 'decade of Venus' exploration may bank on 1 probe - Space.com.
7. Envision factsheet - European Space Agency.
8. Venus Life Finder (VLF) - Gunter's Space Page.
9. Venus Climate Orbiter "AKATSUKI" Operation Completed - JAXA, September 18, 2025.
10. Venus: Facts - NASA Science.
11. Venus was wet: a measurement of the ratio of deuterium to hydrogen - Donahue, Hoffman, Hodges and Watson, Science 216, 1982, via NASA Technical Reports Server.
12. Venus has almost no water: a new study may reveal why - ScienceDaily, reporting Chaffin et al., Nature, May 2024.
13. How waves and turbulence maintain the superrotation of Venus' atmosphere - ISAS / JAXA, April 2020, on Horinouchi et al., Science.
14. Mysterious missing component in the clouds of Venus revealed - University of Cambridge, January 2024, on Jiang et al., Science Advances.
15. Researchers deal a blow to theory that Venus once had liquid water on its surface - University of Cambridge, December 2024, on Constantinou, Shorttle and Rimmer, Nature Astronomy.
16. DAVINCI Science - NASA Science.
17. Life on Venus? UK probe could reveal the answer - Royal Astronomical Society, July 2025.
18. JCMT-Venus: monitoring phosphine and other molecules in Venus's atmosphere - East Asian Observatory / James Clerk Maxwell Telescope.
19. Venera - NASA Goddard Space Flight Center.
20. Vega balloon data - NASA Planetary Data System, Atmospheres Node.
21. Magellan - NASA Science.
22. Venus Magellan Impact Crater Database - US Geological Survey, Astrogeology Science Center.
23. A comprehensive map of the volcanoes on Venus, all 85,000 of them - SpaceNews, March 2023, on Hahn and Byrne, JGR Planets.
24. NASA's Magellan Data Reveals Volcanic Activity on Venus - NASA Jet Propulsion Laboratory, March 2023, on Herrick and Hensley, Science.
25. Ongoing Venus Volcanic Activity Discovered With NASA's Magellan Data - NASA Jet Propulsion Laboratory, May 2024, on Sulcanese et al., Nature Astronomy.
26. NASA's Magellan Mission Reveals Possible Tectonic Activity on Venus - NASA Jet Propulsion Laboratory, May 2025, on Cascioli et al., Science Advances.
27. Bizarre Venus surface formations puzzle planetary scientists - Phys.org, May 2026, on work presented at EGU 2026.
28. First evidence of a subsurface lava tube on Venus - Phys.org, February 2026, on Bruzzone et al., Nature Communications.
29. New evidence points to Venusian lava tubes, and they're really big - Eos, American Geophysical Union, March 2026.
30. The FY 2027 NASA budget request - The Planetary Society, April 2026.
31. DAVINCI, a return to Venus' clouds - The Planetary Society.
32. VERITAS Venus mission seeks to avoid further delays - SpaceNews, November 2024.
33. Signed and sealed: Envision can move towards construction - European Space Agency, January 2025.
34. Then There Were 3: NASA to Collaborate on ESA's New Venus Mission - NASA Jet Propulsion Laboratory.
35. ESA studying impacts of proposed NASA budget cuts - SpaceNews, June 2025.
36. India approves moon sample return, Venus orbiter, space station module and reusable launcher - SpaceNews, September 2024.
37. Venus atmosphere sample return noted in China's long-term space science roadmap - SpaceNews, October 2024.
38. Rocket Lab and MIT's Venus Life Finder mission - The Planetary Society.
39. 2012 Transit of Venus - NASA Goddard Space Flight Center.
40. Juice team resolves anomaly on approach to Venus - European Space Agency, August 2025.