Is There Life on Venus?
The short answer
Maybe, but only in the clouds, and nobody knows yet. In 2020 astronomers reported a gas there called phosphine. In nature, it comes from places where microbes live without oxygen, such as swamp mud and penguin colonies. About 50 km (30 miles) up, the air pressure is close to Earth's. Later checks found less phosphine, or none.
What the telescopes saw
Astronomer Jane Greaves and her team first saw the signal in 2017 with the James Clerk Maxwell Telescope in Hawaii. It was a small dip in the light from Venus, at the wavelength phosphine absorbs. The team checked it with ALMA in Chile in 2019 and announced it on September 14, 2020.
On Earth, phosphine comes from factories and from places where microbes live without oxygen, such as marshes, lakes and sludge. In one Antarctic study, soils in a penguin colony gave off the most. The team named life as one possible cause, next to chemistry nobody understands yet.
Why the clouds and not the ground
At the ground, the air presses down about 90 times harder than ours. That's like being more than 930 m (3,000 ft) under water. It's about 465 °C (870 °F), well above the 327.5 °C (621.5 °F) where lead melts. Ten Soviet landers made it down. The toughest, Venera 13, sent data for 127 minutes.
Higher up, it gets milder. Near 50 km (31 miles) the pressure matches Earth's, though it's still about 75 °C (167 °F). By 55 km (34 miles) it's about 27 °C (81 °F), like a summer day. Venus's air is 96.5 percent carbon dioxide, which is heavier than the nitrogen and oxygen we breathe. So a balloon of plain air would float there, with about half the lift helium gives on Earth.
Then the checks came in
ALMA's data had a calibration problem. After it was fixed, the team's own ALMA figure fell to about 1 to 4 parts per billion, averaged over the planet. The 2020 headline figure, about 20 parts per billion, came from the Hawaii telescope. In November 2021, SOFIA, a flying telescope, looked three times and found none. A University of Washington team argued in 2021 that the signal was more likely ordinary sulfur dioxide, coming from about 80 km (50 miles) up or higher, far above the clouds.
The original team says it has seen phosphine again since then. Others say newer evidence does not support it. No probe that could settle it is on its way yet. NASA's planned Venus missions, DAVINCI and VERITAS, were saved from cancellation by Congress but have not launched.
Key numbers
| What | Number | Source |
|---|---|---|
| Phosphine reported in the clouds in 2020 | about 20 molecules in every billion | MIT News, 2020 |
| Phosphine in the team's reprocessed ALMA data | about 1 to 4 parts per billion, averaged over the planet | Greaves et al. 2021, Nature Astronomy (reanalysis) |
| SOFIA's search, three flights in November 2021 | none found, with an upper limit of 0.8 parts per billion between 75 and 110 km up | Cordiner et al. 2022, SOFIA |
| Air pressure at the surface | 92 bar, about 90 times Earth's | NASA NSSDC, Venus fact sheet |
| Water depth on Earth with the same squeeze | more than 930 m (3,000 ft) | NASA, Venus facts |
| Surface temperature | about 465 °C (870 °F) | NASA NSSDC, Venus fact sheet |
| Melting point of lead | 327.5 °C (621.5 °F) | WikiJournal of Science, Lead |
| Soviet landers that reached the surface | 10 | Astronomy.com, spacecraft that landed on Venus |
| Longest any lander lasted on the surface | 127 minutes (Venera 13) | Guinness World Records, longest time survived on Venus |
| Air 50 km (31 miles) up | about 1.07 atmospheres and 75 °C (167 °F) | Wikipedia, Atmosphere of Venus (VIRA table) |
| Air 55 km (34 miles) up | about 27 °C (81 °F) | Wikipedia, Atmosphere of Venus (VIRA table) |
| Lift of plain Earth air near 50 km | about 0.5 kg per cubic meter, about half what helium lifts on Earth | Landis 2003, NASA Technical Reports Server |
What the film simplifies
- The film says that in nature phosphine is made by microbes. Factories make it too, and nobody has yet shown which microbe makes it or how. It is linked to places where microbes live without oxygen.
- "About thirty miles up" is where the pressure matches Earth's, but it's still about 75 °C (167 °F) there. The summer day warmth comes near 55 km (34 miles). NASA's own page gives 30 to 70 °C (86 to 158 °F) at 50 km.
- Ten Soviet landers made it down, but one of them, Vega 1, switched on its surface experiments early, about 20 km up, and sent almost no science from the ground. Venera 13 ran for at least 127 minutes. Its signal ended when the spacecraft relaying it flew out of range.
- The film lists only the doubts. The lower amount came from the original team's own reanalysis, and since 2022 that team reports seeing phosphine again. The film also skips where the signal comes from: the team placed it in the clouds, and the sulfur dioxide papers place it above 80 km.
- Rocket and the penguin are cartoon. Greaves has said her team never suggested penguins on Venus. The penguin is drawn as an Adélie, which nests in the colony that was studied, though gentoos are the most common penguins there.
- The film lines up the ten landers on one stretch of ground. On Venus they lie far apart, spread across the planet.
At a glance
Runtime 1 minute 3 seconds · Topics: Venus, Life beyond Earth, Atmospheres, Telescopes · Captions on YouTube · Full script below
Test yourself
The ground on Venus is about 465 °C (870 °F). Why do scientists look for life in the clouds instead?
Answer
About 50 km up the air pressure matches Earth's, and near 55 km the temperature is about 27 °C (81 °F), like a summer day. At the ground the air presses about 90 times harder than ours and is hot enough to melt lead.
Why would a balloon full of plain Earth air float in the clouds of Venus?
Answer
Venus's air is 96.5 percent carbon dioxide, which is heavier than the nitrogen and oxygen in our air. So our air is a lifting gas there, with about half the lift helium has on Earth.
Finding phosphine on Venus would not prove there is life there. Give two reasons from this page.
Answer
Phosphine could also come from chemistry nobody understands yet, and on Earth factories make it, so life is only one possible cause. Also, later checks lowered the amount, found none at all, or said the signal was sulfur dioxide.
The script
Host: In 2020, astronomers reported a possible sign of life on Venus.
Rocket: Aliens! I'm gonna meet 'em first!
Host: Astronomer Jane Greaves had spotted a gas in its clouds:
Host: phosphine. In nature, it's made by microbes in swamp mud... and penguin poop.
Rocket: So I brought an expert!
Host: On the ground, the air presses down ninety times harder than ours. Like half a mile under the sea.
Rocket: Worth it!
Host: And it's 870 degrees. Lead melts.
Rocket: Still worth it!
Host: Ten Soviet landers made it down. The toughest lasted about two hours.
Rocket: Two hours? I'll stay all day!
Rocket: NOT worth it!
Host: But about thirty miles up, the air pressure is like Earth's.
Host: A few miles higher, it's as warm as a summer day.
Host: Our air is lighter than Venus's, so a bubble of it floats, like a helium balloon.
Rocket: So the aliens live up here too!
Host: Then other astronomers checked. Some found nothing, and some say it's a different gas.
Host: So is there life on Venus? Nobody knows yet.
Rocket: Sure there is. I brought some!
Sources
- Phosphine announced in Venus's clouds on September 14, 2020, at about 20 molecules per billion, with the James Clerk Maxwell Telescope in Hawaii and ALMA in Chile.MIT News, 2020
- The detection paper; the authors give unknown photochemistry or geochemistry, or life, as possible causes.Greaves et al. 2020, Nature Astronomy
- Cardiff University release: a possible sign of life on Venus; phosphine on Earth made only industrially or by microbes.Cardiff University via ScienceDaily, 2020
- JCMT observed Venus in 2017 and ALMA in 2019; the original team reports seeing phosphine again; the editor's note says newer evidence does not support it.The Planetary Society, Life on Venus updates
- Greaves's team observed Venus with the James Clerk Maxwell Telescope in Hawaii in June 2017.Yale Scientific, Jane Greaves
- On Earth phosphine is linked to microbes in places without oxygen, such as wetlands, marshes, lakes, sludges and penguin colonies, and is also made industrially; how microbes make it is unknown.Phosphine as a Biosignature Gas in Exoplanet Atmospheres, 2019
- Soils in an Antarctic penguin colony give off the most phosphine.Zhu et al. 2014, penguin colony soils
- Phosphine on Earth comes from microbes, swamps and penguin guano.The Register, 2020
- Phosphine on Earth comes from microbes, swamps and penguin guano.Astronomy.com, phosphine on Venus
- Surface pressure 92 bar, surface temperature 464 °C, air 96.5 percent carbon dioxide.NASA NSSDC, Venus fact sheet
- Hot enough to melt lead; pressure like more than 930 m (3,000 ft) under water; about 50 km (30 miles) up the pressure is similar to Earth's surface and it is 30 to 70 °C (86 to 158 °F).NASA, Venus facts
- Lead melts at 327.5 °C (621.5 °F).WikiJournal of Science, Lead
- Ten Soviet landers reached the surface of Venus.Astronomy.com, spacecraft that landed on Venus
- Venera 13 survived 127 minutes on the surface.Guinness World Records, longest time survived on Venus
- Venera 13 and the first colour images from the surface.Space.com, Venera 13
- About 50 km up is the most Earthlike environment in the solar system other than Earth; breathable air is a lifting gas there, with about half the lift helium has on Earth.Landis 2003, NASA Technical Reports Server
- Temperature and pressure by height: 50 km about 75 °C and 1.07 atmospheres, 55 km about 27 °C.Wikipedia, Atmosphere of Venus (VIRA table)
- After a calibration issue, the reprocessed ALMA data give about 1 to 4 parts per billion averaged over the planet; the JCMT detection was about 20 parts per billion.Greaves et al. 2021, Nature Astronomy (reanalysis)
- SOFIA found no phosphine in three flights in November 2021, upper limit 0.8 parts per billion between 75 and 110 km.Cordiner et al. 2022, SOFIA
- The signal is more likely ordinary sulfur dioxide, from 50 or more miles up, far above the clouds.University of Washington News, 2021
- Phosphine and sulfur dioxide lines can't be separated in the data.Villanueva et al. 2021
- Congress saved NASA's DAVINCI and VERITAS missions from cancellation.Sky & Telescope, NASA's budget woes are over for now