Sunlight passes through Venus’ atmosphere
1 When Venus passes in front of the Sun as observed from Earth, some sunlight passes through its atmosphere before reaching Earth. This can be recorded using telescopes, then by studying the wavelengths that reach us, the formulation of the planet’s atmosphere can be determined.
Molecules absorb and reflect the light
2 The atmosphere’s molecules absorb light at specific wavelengths and reflect or bend light at other wavelengths. In this way, the molecules leave different ‘fingerprints’ on the light for astronomers to measure. Oxygen has one print, while phosphine (PH3) has another one.
Wavelengths reveal biological marker
3 Measurements made by the JCMT and ALMA telescopes show fading sunlight at a specific wavelength – 1.123mm – corresponding to phosphine (PH3) having absorbed some of the light. The high quantities are difficult to explain without the presence of life.
If we could travel back in time two billion years and then visit our neighbouring planet of Venus, we would probably find a world fairly similar to our own home planet today – maybe even with biological life on the surface. But millions of years of climate change since then have converted Venus into the red-hot
