Highly Allochthonous

One of the main risks of our media-saturated world is that although events can make it onto our TV and computer screens with unrivaled speed, this does not necessarily mean we have any idea of what's actually going on, which often leads to the speculation getting a bit out of hand. Last weeks extra-terrestrial events in Peru are a case in point. Meteorite impact? Yes - the coincidence of a previously unnoticed hole and something falling from the sky close to where it appeared made that reasonably likely. Alien contagion about to wipe us all out? Only in the dreams of the nuttiest panspermia advocates. If the meteorite had happened to be a carbonaceous chondrite, then it was vaguely possible that something non-biological from the meteorite, within the gases emanating from the impact site, was causing nausea and headaches amongst the locals. However, by far the most reasonable, if the most mundane, explanation, was the one offered by the BBC, who actually bothered to ask someone who might know what they're talking about:

A local journalist, Martine Hanlon, told the BBC experts did not believe the meteor would make anybody sick, but they did think a chemical reaction caused by its contact with the ground could release toxins such as sulphur and arsenic.

And, lo and behold, that's pretty much the right explanation, according to a Peruvian geologist who went to have a look:

The illness was the result of inhaling arsenic fumes, according to Luisa Macedo, a researcher for Peru's Mining, Metallurgy, and Geology Institute (INGEMMET), who visited the crash site.

The meteorite created the gases when the object's hot surface met an underground water supply tainted with arsenic, the scientists said.

Numerous arsenic deposits have been found in the subsoils of southern Peru, explained Modesto Montoya, a nuclear physicist who collaborated with the team. The naturally formed deposits contaminate local drinking water.

"If the meteorite arrives incandescent and at a high temperature because of friction in the atmosphere, hitting water can create a column of steam," added José Ishitsuka, an astronomer at the Peruvian Geophysics Institute, who analyzed the object.

Hopefully no-one is too disappointed that humanity is not going to have it's blood crystallised....