It has been suggested that dust storms on Mars might generate electric fields large enough to produce lightning-like electrical discharges, and a recent study reported evidence of such lightning. If lightning does occur on Mars, it could present a hazard for spacecraft or manned missions to the planet. However, Gurnett et al. report that a 5-year search using a radar receiver on board the Mars Express spacecraft found no evidence of lightning at frequencies between 4.0 and 5.5 megahertz, although there were two major dust storms and many smaller storms during the time period. The search does not rule out the possibility of lighnting on Mars at substantially higher or lower frequencies.