SPACE – Why deep space would smell quite bad

If you could smell deep space, it wouldn’t be a very pleas­ant ex­pe­ri­ence at all. JOEL F. HOOPER re­ports.

Cosmos - - Digest -

Smell is per­haps our most mys­te­ri­ous sense, per­haps be­cause it can trig­ger mem­o­ries and link us to spe­cific times and places. So it’s not sur­pris­ing that we of­ten won­der what dis­tant and ex­otic places would smell like – think of the fre­quent men­tion of odour in Gul­liver’s Trav­els, or Pro­fes­sor Farnsworth’s Smell-o-scope in Fu­tu­rama.

Thus, set­ting aside the prac­ti­cal prob­lems of try­ing to take a lung­ful of vac­uum, what would it be like to get a whiff of the sparse gases and par­ti­cles that oc­cupy deep space?

If we turn our nose to Sagit­tar­ius B2, a cloud of gas about 390 light years from the cen­tre of the Milky Way, we would en­counter a host of ol­fac­tory de­lights. Al­most ev­ery chem­i­cal that has been de­tected in space can be found there.

Among the smellier com­po­nents of Sagit­tar­ius B2 is hy­dro­gen sul­fide (H2S), of­ten de­scribed as rot­ten-egg gas.

This chem­i­cal can be de­tected at around 10 bil­lion mol­e­cules per cu­bic cen­time­tre by the hu­man nose, and can cause death in high con­cen­tra­tions. At its most dense, the Sagit­tar­ius cloud con­tains only about one mil­lion mol­e­cules per cu­bic cen­time­tre, about 10,000 times be­neath the hu­man thresh­old.

We might also en­counter hy­dro­gen cyanide (HCN), an­other deadly gas, though this one smells of bit­ter almonds. Chemists in the early 20th cen­tury used to smoke cig­a­rettes while work­ing with this chem­i­cal, be­cause a re­lease of hy­dro­gen cyanide would change the flavour of the to­bacco and act as an early warn­ing sign of any leak.

There are also much more agree­able odours in space. Ethyl for­mate be­longs to a class of mol­e­cules called es­ters, which of­ten have sweet and fruity aro­mas. It is one of the chem­i­cals re­spon­si­ble for the smell of rasp­ber­ries.

Space is also home to com­pounds called pol­yaro­matic hy­dro­car­bons, flat mol­e­cules made up of rings of car­bon atoms. These chem­i­cals were named “aro­matic” by early chemists be­fore their struc­ture was known, due to the strong smells they pro­duce. Their fra­grances range from faintly pleas­ant to the strong smell of coal tar. A study pub­lished re­cently in The Astro­phys­i­cal Jour­nal found they are present in much higher con­cen­tra­tions than pre­vi­ously thought, es­pe­cially in older gal­ax­ies.

The main dif­fer­ence be­tween the gases of space and those in our own at­mos­phere is the abun­dance of oxy­gen on Earth, mean­ing that many smelly chem­i­cals based on sul­fur or phos­pho­rus ex­ist here in their milder, ox­i­dised forms. We must con­clude, there­fore, that a deep whiff of space gas would prob­a­bly smell clos­est to rot­ting garbage, fish or flatulence.



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