In the last few years NASA has built and launched two world-class climate satellites, both of which promised invaluable new data on the natural and human influences on Earth's changing climate. Neither of them, however, will ever deliver the data that climate scientists so eagerly expected from them. Both spacecraft, in fact, are at the bottom of the ocean, having succumbed to nearly identical rocket mishaps that prevented them from reaching orbit.

The latest incident occurred in the wee morning hours of March 4, just after the Glory spacecraft lifted off atop a Taurus XL rocket from Vandenberg Air Force Base in California. About three minutes into the flight the protective nose cone, or fairing, enshrouding Glory failed to separate from the rocket as commanded, and the entire assembly came tumbling back to Earth. That is just what happened in February 2009, when NASA's Orbiting Carbon Observatory (OCO) blasted off on board another Taurus XL rocket and came crashing down in the waters off Antarctica.

"All indications are that the satellite and rocket are in the southern Pacific ocean somewhere," NASA launch director Omar Baez said of Glory in a somber March 4 news conference following the liftoff. Given the comparable launch weights of Glory and the OCO and the similarity of the malfunction, Glory may have ended up in close proximity to its fellow climate satellite. "Physics says it's likely in the same spot or close to it," Baez said.

Glory was to monitor the intensity of solar energy reaching Earth's upper atmosphere and to measure airborne atmospheric particles that affect how much of that energy reaches the surface. Those measurements would have reduced uncertainties in models that project future climate trends and helped to sort out how much climate influence man-made aerosols such as soot and smoke have compared with natural sources such as sea spray and airborne soil particles.

"It would have made important measurements for the understanding of Earth as a system," Mike Luther of NASA Headquarters said in the press conference. Climate modeler Gavin Schmidt of the NASA Goddard Institute for Space Studies, writing at the blog RealClimate, called Glory one of the most important satellites in ages. Its ability to not only measure aerosols but to distinguish between different kinds of aerosols would have been unique, Schmidt wrote. "It may seem surprising, but despite many different attempts [so far], almost all remote sensing of aerosols from space is only capable of detecting the total optical depth of all aerosols," he wrote. "Because we can't easily distinguish what's what from space, we don't have good global coverage of exactly how much of the aerosol is anthropogenic, and how much is natural."

At the moment, NASA has no plans for a replacement, says NASA spokesperson Steve Cole. In the case of OCO, NASA was able to fund a replacement mission, now in development for a 2013 launch. "Judging by what happened with OCO two years ago, it will take many months to make a decision as to which path to pursue," Cole says.

Orbital Sciences Corp., which operates the Taurus XL, said that it had made significant changes to the system that triggers the separation of the fairing from the rocket since the 2009 OCO mishap. "We went so far as to completely change out the initiation system, and in the intervening years that system flew three times," Orbital Sciences's executive vice president, Ronald Grabe, said at the news conference. "We went into this flight really feeling that we had nailed the fairing issue."

Luther said that NASA had been comfortable using the Taurus XL again. "We felt going in that we had an acceptable level of risk," he said. "Clearly we missed something." He added that the mishap might affect the launch of the replacement Orbiting Carbon Observatory, OCO 2, which is also scheduled to ride into orbit on a Taurus XL. "We'll have to evaluate the outcome of this investigation and adjust our plans appropriately," Luther said.