  Space-based instruments provide new and, in some cases, unique opportunities
to search for dark matter. In particular, if dark matter comprises sterile
neutrinos, the x ray detection of their decay line is the most promising
strategy for discovery. Sterile neutrinos with masses in the keV range could
solve several long-standing astrophysical puzzles, from supernova asymmetries
and the pulsar kicks to star formation, reionization, and baryogenesis. The
best current limits on sterile neutrinos come from Chandra and XMM-Newton.
Future advances can be achieved with a high-resolution x-ray spectrometry in
space.
