Not really an expedition, but this seemed the most suitable board to put this in...

On the Wonders of Life show, presented by Brian Cox, he visited cenotes in Yucat?n and a Hydrogen Sulphide rich cave. Interestingly he showed that the cenotes were distributed around the edge of the Chicxulub crater.

It's on iPlayer until 5th March: http://www.bbc.co.uk/iplayer/episode/b01r1znn/Wonders_of_Life_Home/

And said:

Interestingly he showed that the cenotes were distributed around the edge of the Chicxulub crater.

Click to expand...

Yes - it was first discussed in Ring of Cenotes (sinkholes), northwest Yucatan, Mexico: Its hydrogeologic characteristics and possible association with the Chicxulub impact crater by  Eugene Perry et al in the January 1995 edition of the journal Geology.

These caves were also shown breif on a program that was on tonight about metorites.