The other hypothesis is that the dose is an act of blatant favouritism, aimed primarily at sons by mothers who are attempting to pull a fast one on their potential daughters-in-law.

ECONOMIST: Animal behaviour

"The thing that really struck the science team about this image is that you would really be forgiven for thinking that NASA was trying to pull a fast one on you and we actually put a rover out in the Mojave Desert and took a picture -- a little L.A. smog coming in there, " he said.

CNN: Mars rover captures nearby rocket 'footprint'