Very few road trips go exactly according to plan and that goes double for ones on Mars. At the start of its third year on the Red Planet, NASA’s Curiosity rover was slated to head for the "Pahrump Hills" for its fourth rock drilling exercise, but after encountering unexpectedly hazardous terrain, it’s making a detour to a similar site called "Bonanza King" to carry on its mission.
Curiosity may be a marvel of engineering and is frequently compared to a 4x4 because it’s the size of one, but the unmanned rover is not exactly in the same league as a Series 2 Land Rover. Terrain can be a problem and after getting the Spirit rover hopelessly stuck in soft Martian sand in 2009, NASA isn't keen to repeat the accident.
In addition, Curiosity’s aluminum wheels have been showing more signs of wear than was anticipated due to sharp rocks, and they've been slipping in the sand that it’s been traversing lately, so NASA is being very cautious. The area that Curiosity was originally scheduled to cross, called Hidden Valley, is covered from end to end and wall to wall with rippling sand and engineers weren't keen on running the risk of tackling more sand than the rover had encountered outside of the dunes of California.
So, when the nuclear-powered explorer encountered the sand in Hidden Valley, mission control had second thoughts and ordered Curiosity to back up and forget about Pahrump Hills in favor of Bonanza King. According to NASA, this is no great loss because the two areas are geologically connected. The space agency is keen to look at this particular formation because it's different from the crater floor formations encountered so far and will provide more insights into the history of the planet.
Engineers are studying Bonanza King to see if its is suitable for drilling by assessing whether or not the plates seen on the surface are loose. When drilling operations resume, NASA will study alternative routes to Curiosity’s final destination of Mount Sharpe and determine how well the rover’s wheels can handle sand ripples.
Curiosity has been on Mars for two years as it continues its mission to study the weather and geology of Mars in search of areas that could or once could have supported microbial life.