An independent panel of scientists slammed the $2.5 billion Curiosity Mars rover's management team in a report released Wednesday, saying the mission's plan "lacked scientific focus and detail."

Artist's concept of the Curiosity rover. Credit: NASA/JPL-Caltech
 
The review board accused the rover's ground team of inadequately using the rover for science and ranked Curiosity's scientific merit near the bottom of a list of missions under consideration for extensions.

The biennial senior review issues recommendations to NASA on whether the agency should grant funding to continue operating probes beyond their primary missions. The missions up for extensions this year were Curiosity, the Cassini spacecraft orbiting Saturn, the Opportunity Mars rover, the Lunar Reconnaissance Orbiter, the Mars Reconnaissance Orbiter, the Mars Odyssey probe, and U.S. contributions to the European-led Mars Express orbiter at the red planet.

NASA awarded two-year extensions to all of the missions except Cassini, which was promised three years of funding until it is scheduled for a controlled crash into Saturn in 2017.

"The senior review committee came back and said unequivocally that these are all extremely important missions," said Jim Green, director of NASA's planetary science division. "They really are a big bang for a buck because they're in place and making great measurements, and we don't have to launch them. They're really cost-effective for the American people."

But Curiosity, one of NASA's most recognizable science missions, was ranked near the bottom of the senior review report's ratings. Cassini's proposal for a mission extension received the best grade from the senior review.

The 15-person senior review was chaired by Clive Neal, a professor in engineering and Earth sciences from the University of Notre Dame.

In a letter to Green, Neal wrote that the review board found holes in the proposal submitted by Curiosity rover scientists, saying that the senior review found the rover's mission plan "lacked scientific focus and detail."

Neal wrote that the panel was surprised by the weakness of the Curiosity extended mission proposal.

"The proposal lacked specific scientific questions to be answered, testable hypotheses, and proposed measurements and assessment of uncertainties and limitations," Neal wrote.

According to the letter, Curiosity's project scientist was not present during the board's meetings to answer questions about the mission in person.

"This left the panel with the impression that the team felt they were too big to fail and that simply having someone show up would suffice," Neal wrote. "The panel strongly urges NASA [Headquarters] to get the Curiosity team focused on maximizing high-quality science that justifies the capabilities of and capital investment in Curiosity."

Curiosity received about $60 million for operations in 2014, making it the most costly operating planetary science mission along with Cassini.

The report charged Curiosity's science team of inadequately utilizing the rover's scientific capabilities, such as the ability to detect life-supporting minerals in Martian soil.

The two-year mission plan submitted by Curiosity scientists called for the rover to collect eight rock samples with its drill for delivery into the craft's internal scientific laboratory, a miniaturized suite of spectrometers and chemistry instruments to measure the rock powder's make-up.

"The panel viewed this as a poor science return for such a large investment in a flagship mission," Neal wrote.

In the board's findings, the review scientists wrote that Curiosity's science team did not detail how the rover's cameras would identify rock targets for close-up scrutiny.

Since it landed Aug. 6, 2012, Curiosity has logged more than 8 kilometers, or 5 miles, driving across the floor of Gale Crater, a 96-mile-wide impact basin.

Curiosity is driving toward Mount Sharp, a three-mile-high peak thought to harbor clays and sulfates pointing to the red planet's ancient past. Officials expect the rover to arrive at the base of the mountain before the end of the year.

Scientists say the clays formed in the presence of water, making the deposits ripe for investigations focusing on probing the red planet's potential for hosting primitive life when Mars was warmer and wetter.

Balancing the rover's drives with periodic stops for science, a question often discussed within Curiosity's own science team, was also identified as a key issue by the review board. The push-pull dilemma of whether to explore a variety of geologic formations or thoroughly analyze fewer regions is at the crux of the debate.

"The panel is deeply concerned that observations in the clays, which may be more relevant to the habitability question, could be cut short because traverse distance will take precedence over scientific analyses," Neal wrote.

Curiosity's prime mission lasted one Martian year, a milestone reached in late June. NASA needed to give approval for the rover to continue operating beyond this month.

"It was unclear from both the proposal and presentation that the prime mission science goals had been met," Neal wrote. "In fact, it was unclear what exactly these were."

Bill Knopf, NASA's lead program executive for operating planetary science missions, told a NASA advisory committee Wednesday that the space agency agreed that Curiosity's management team should focus more on scientific activities.

NASA asked Curiosity mission officials at the Jet Propulsion Laboratory to come up with a new plan that prioritizes in-depth geologic research and analytical sampling, such as the drilling of rocks, according to Knopf.

Follow Stephen Clark on Twitter: @StephenClark1.