The Universe has proven to be far more intriguing in its composition than we knew it to be. It is a dark Universe where 23% of its mass-energy density is made up of weakly interacting (and, as yet, undetected) non-baryonic particles (a.k.a. dark matter) and 73% is as yet unknown physics (a.k.a. dark energy) that is driving an accelerated expansion. To shed new light on these mysteries, we combine the gravitational lensing power of 25 massive galaxy clusters with HST's enhanced panchromatic imaging capabilities (WFC3 and the restored ACS) to test structure formation models with unprecedented precision. We have dubbed our program CLASH, which stands for:

Cluster Lensing And Supernova survey with Hubble.