After weeks in space, the inside of an astronaut’s spacesuit probably starts to smell pretty ripe. If we ever send humans to the Comet 67P, the outside of their suits may smell even worse. That’s what the Rosetta spacecraft is reporting as it gets close enough to the comet for its on-board olfactory sensors to get a whiff.
Visual images from a few weeks ago showed some small jets emanating from the so-called “neck” region of the duck-shaped comet. The latest photos show that the comet is spraying more, the jets are bigger and the emissions are coming from a much larger surface area. Comet 67P is currently 450 million km from the Sun and this activity is expected to increase dramatically once it gets to within 300 million km of it.
And how do those emissions smell? According to the latest release from the European Space Agency on measurements taken by the two mass spectrometers in the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA), it’s pretty bad. Let’s start with the hydrogen sulfide, which has the odor of rotten eggs. Add some ammonia, which is what gives barn animal urine its unique smell (and why lemon-scented cleaners are so popular). Combine with some formaldehyde, sulfur dioxide and carbon disulfide and you can’t even notice the one pleasant sniff in the mix – a little hydrogen cyanide which smells like almonds.
The good news is that the density of the molecules in the odor is pretty low, so you need more sensitive instruments than the human nose to pick it up. Even better, the aroma is a signature that will help identify and compare comets to determine where in the solar system they came from.
In space, no one can hear you scream but they can definitely smell your emissions.