As any travel agent knows, it’s all about the weather. Accommodations may be luxurious and the food exquisite, but future daytrippers to Mars will require predictable climes for successful missions, scientists with NASA’s Langley Research Center said yesterday. Even with timely forecasts from on-the-scene orbiters circling the Red Planet, NASA was still surprised by the elements as the rovers Spirit and Opportunity came in for their landings.