On August 5, 2012, at 10:32 pm PDT, a landing signal that had been sent 14 minutes earlier from the surface of Mars finally reached Earth, confirming that the robotic explorer Curiosity had successfully touched down.
That was after the vehicle traveled through the vacuum of space for nine months, plunged through the Martian atmosphere at 13,000 mph, and slowed down to about 900 mph via a 60-foot wide parachute. Then, Curiosity’s rocket-powered sky crane gently lowered the 1-ton rover to planet’s dusty red surface.
Celebrating Curiosity in Tucson
At that moment, here at the Lunar and Planetary Laboratory in the Michael J. Drake Building at the University of Arizona, attendees at an event hosted by Dean Joaquin Ruiz and the College of Science watched the landing via a real-time video feed from the Jet Propulsion Laboratory control room. All in attendance marveled at the dazzling display of technological prowess.
The event evoked memories of other great UA Mars mission successes, such as the 2005 HiRISE High Resolution Imaging Science Experiment and the 2008 Phoenix Mars Mission.
While the crowd rejoiced, three UA community members got to celebrate the triumph personally, for their hands and minds helped shape – and will continue to shape – the 2-year interplanetary expedition.
The 6-wheeled Curiosity rover, about the size of a compact car, carries 10 scientific instruments. UA investigators are working directly on two of them.
Fingers in the Soil
Robert Downs, PhD, professor of geosciences, is co-investigator working on the chemistry and mineralogy instrument that will analyze powdered rock and soil samples delivered by Curiosity’s robotic arm. His assistant on the project is Shaunna Morrison, a graduate student in the geosciences and rare earth mineralogy.
Downs and Morrison, NASA-designated PDLs or “payload downlink leads,” are members of the science team in charge of the CheMin instrument. CheMin, short for chemistry and mineralogy, is the first X-ray diffractometer ever sent to space, said Downs.
“It works by shooting X-rays at a rock sample, which interact with the electrons in the rock and send back signals that are like fingerprints,” Downs explains. “It's the standard for identifying minerals, just what you would do in a lab here on Earth.”
Once CheMin finishes analyzing a rock sample, which can take up to 10 hours, Curiosity will send the data to Earth, where Downs and Morrison will be among those who gather the data and interpret them.
Searching for Water
Simultaneously, William V. Boynton, PhD, of the Lunar and Planetary Laboratory, is working on the Dynamic Albedo of Neutrons instrument, known as DAN, which will shoot neutrons into the ground and measure how they are scattered. Neutrons that collide with hydrogen atoms bounce off with a characteristic decrease in energy. By measuring the energies of the reflected neutrons, DAN will detect the fraction that was slowed in these collisions and therefore detect the amount of hydrogen present.
Because water contains hydrogen in exact proportions, scientists will use the data from DAN to formulate measurements of the distribution of water and ice in the upper 1 to 2 meters of the Martian soil.
Eyes in the Sky
The instantly famous image of Curiosity’s descent, snapped about 1 minute before touchdown, was taken by the High-Resolution Imaging Science Experiment (HiRISE), the UA-operated camera aboard the Mars Reconnaissance Orbiter, which arrived at the Red Planet in 2006. Since that time, HiRISE has been taking the highest-resolution images and 3-D stereograms of the planet’s surface ever captured.
"We have been planning this for some time," said Alfred McEwen, a professor in the University of Arizona Lunar and Planetary Laboratory and principal investigator of HiRISE. "We gradually adjusted MRO's orbit to make sure it would be right over Curiosity as it landed, and that put us in a great position for this image. It came back exactly as we expected in terms of brightness and contrast. The parachute looked beautiful, nice and sharp, fully inflated and working perfectly."
The snap shot required months of preparations to make sure the two spacecraft, traveling in directions perpendicular to each other and at several miles per second in the case of MRO, wouldn't miss each other. McEwen said it would have been great to have the descent image in color, but because HiRISE's color channel has a narrower field of view than the black and white channels, that wasn't possible under the circumstances.
"It's a good thing our field of view wasn’t very much narrower or we could have missed it entirely," McEwen said.
Morrison said of the celebration, "I felt so fortunate to be a part of such an important moment! Everyone, including myself, was so excited - the energy in the room was incredible!"
But now that the dust is settling, a new sense of purpose has set in amongst the scientists as the ground mission gets underway.
“There is a carnival excitement here, and it’s easy to get caught up in it,” Downs said on August 6, the day after touchdown. “But the real work is ahead. Tomorrow, my shift is 11:00 pm - 6:00 am. So, I suspect that I will feel tired.”
Over the next 2 years, Curiosity will take a slow, plodding road trip, venturing 12 miles from its landing site and collect, grind and analyze about 70 samples of soil and rock.
Asked if he expected to find any mineral on Mars that does not occur on Earth, Downs said, “I don't know. Probably not, but I hope there is something new. Just for the challenge, you know?”