  Cloud computing is a powerful new technology that is widely used in the
business world. Recently, we have been investigating the benefits it offers to
scientific computing. We have used three workflow applications to compare the
performance of processing data on the Amazon EC2 cloud with the performance on
the Abe high-performance cluster at the National Center for Supercomputing
Applications (NCSA). We show that the Amazon EC2 cloud offers better
performance and value for processor- and memory-limited applications than for
I/O-bound applications. We provide an example of how the cloud is well suited
to the generation of a science product: an atlas of periodograms for the
210,000 light curves released by the NASA Kepler Mission. This atlas will
support the identification of periodic signals, including those due to
transiting exoplanets, in the Kepler data sets.
