Venus is almost the same size as Earth, made of roughly the same stuff, and sits just one planet closer to the Sun. It is also the most hostile place in the inner Solar System: a surface hot enough to melt lead, pressed under an atmosphere as heavy as the ocean at 900 metres deep, under clouds of sulfuric acid. After a long gap, three major missions are now heading back, and the question they're asking has become unexpectedly interesting.
What Makes Venus Hostile
The defining fact about Venus is its atmosphere. It is 96.5 percent carbon dioxide, about 90 times denser at the surface than Earth's, and traps heat so efficiently that the surface temperature barely varies between day and night or equator and poles. At roughly 465 °C, it is hotter than Mercury's dayside — despite being nearly twice as far from the Sun — purely because of the greenhouse effect.
Above the surface, three distinct cloud decks of sulfuric acid droplets wrap the planet from about 48 to 70 km altitude. Those clouds are highly reflective, which is why Venus is the brightest natural object in the night sky after the Moon. They also hide the surface completely from visible light. Every map of the Venusian surface ever made has come from radar, either from orbit (NASA's Magellan in the early 1990s) or from the short-lived Soviet Venera landers.
Venus rotates backwards relative to its orbit and does so extraordinarily slowly. A Venusian solar day is 117 Earth days; its sidereal rotation is 243 Earth days, longer than its 225-day year. The atmosphere, by contrast, super-rotates around the planet in about four Earth days, a mystery that is still not fully explained.
Why We Stopped Going
The Soviet Venera programme in the 1970s and 1980s is still the only series of missions that landed anything on the Venusian surface. Venera 7 transmitted for 23 minutes from the surface in 1970; Venera 13 and 14 lasted a bit over two hours each in 1982 and returned the only colour photographs ever taken from the ground. Every lander stopped working within hours — not because the electronics failed, but because the environment cooked them and crushed their pressure vessels.
After Magellan's global radar map in 1990–1994, NASA essentially turned away from Venus for a generation. ESA's Venus Express (2005–2014) and JAXA's Akatsuki (still operating in orbit as of 2025) kept atmospheric science going, but no new surface missions were approved. The reasons were partly engineering — Venus is genuinely hard — and partly that Mars offered a more forgiving target for the same budgets.
Why We're Going Back
Three things changed the calculation. First, planetary scientists now think Venus may have been habitable for billions of years, with liquid water oceans and a milder climate, before something — a runaway greenhouse? Massive volcanic resurfacing? — pushed it across a threshold. Understanding that transition matters for every rocky exoplanet we will ever characterise, because a planet in the habitable zone that went the way of Venus looks very different from one that went the way of Earth.
Second, a 2020 paper reported phosphine in the Venusian cloud deck. Phosphine on rocky planets is, on Earth, a biosignature; no known non-biological process produces it in the quantities claimed. The result has been contested, partially retracted, partially re-asserted, and remains unresolved. Independent confirmation requires instruments that fly through the clouds, not telescopes on Earth.
Third, the engineering for short-duration surface and atmospheric missions has improved enough that a new generation of spacecraft can actually do useful work at Venus without needing to survive indefinitely.
The Next Missions
Three major missions are now in development, representing the first serious return to Venus in over three decades.
- DAVINCI (NASA). A descent probe that will fall through the Venusian atmosphere on parachutes, sampling gases and imaging the surface as it goes, before an unsurvivable surface impact. The mission's central goal is to measure noble gas and trace gas abundances accurately enough to test the "was Venus habitable?" question directly.
- VERITAS (NASA). An orbiter carrying synthetic aperture radar and a near-infrared imager, building a topographic and compositional map of the surface at resolutions Magellan could not reach. VERITAS is the mission that should finally settle whether Venus is still volcanically active on human timescales.
- EnVision (ESA). A complementary ESA orbiter focused on subsurface sounding, atmospheric composition, and high-resolution imaging of targeted regions. EnVision and VERITAS are explicitly designed to produce datasets that complement each other.
All three have had schedule slips. NASA delayed VERITAS's launch once and DAVINCI's profile has been revised. The current working expectation puts first arrivals in the late 2020s or early 2030s. Dates will slip again. The programme direction will not.
Could Humans Ever Go?
Not to the surface. The atmosphere is not survivable by any life-support technology on any reasonable horizon. But Venus has one remarkable feature that shows up in speculative crewed-mission studies: at an altitude of about 50 km, the atmospheric pressure is roughly 1 bar, the temperature is room temperature, and the air, while thick with carbon dioxide and sulfuric acid droplets, is otherwise an ordinary-density environment. A balloon filled with ordinary Earth air would float in it.
That has led to concepts for airship habitats in the Venusian cloud layer — the best-known being NASA's HAVOC study. These are not current programmes, and they do not solve the acid-cloud problem, but they establish that a crewed Venus mission is not physically impossible the way a crewed Jupiter mission is.
See the terraforming and long-term colonisation articles for where speculative Venus thinking fits into the broader picture.
What Venus Is Really For
The short version: Venus is the comparison planet. Mars tells us what happens when a small world loses its atmosphere to space. Venus tells us what happens when a world roughly our size keeps its atmosphere and cooks under it. Exoplanet catalogues already contain thousands of planets that are some version of one or the other. Figuring out which is which, and why, is only possible by studying the two nearby examples in detail. The Venus missions of the late 2020s are the first serious step in that programme since before the Space Shuttle retired.