Mars Curiosity Rover
Jet Propulsion Laboratory, Pasadena, Calif.
NASA Headquarters, Washington
The daily chatter between antennas here on Earth and those on NASA spacecraft at Mars is about to get much quieter for a few weeks.
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown / JoAnna Wendel
NASA Headquarters, Washington
Mission Status Report
Tables stored in flash memory aboard NASA’s Mars Reconnaissance Orbiter (MRO) tell locations of Earth and the sun for the past 10 years, but not their locations next year. That needs to be changed. Carefully.
The long-lived orbiter relies on these tables to recover in the event of an unplanned computer shutdown. When the spacecraft computer reboots, it checks to see where it should position the antenna for communication and, even more critically, where it should position the solar arrays for power. Flash memory is “nonvolatile” — meaning that it retains information even while the power is off — so it works well for this backup role.
The tables were loaded before the spacecraft’s Aug. 12, 2005, launch and they cover location information through July 12, 2016. To be safe, the mission team plans to begin updating them next week. Doing so will require intentionally rebooting the onboard computer during a one-week suspension of MRO’s science observations and communication relay duty. Both of NASA’s active Mars rovers will use a different NASA Mars orbiter, Odyssey, for relaying their data to Earth while MRO is out of service.
Sixteen times since launch, MRO has experienced unplanned reboots that relied on the stored tables for recovery of the spacecraft. Managers anticipate that such events will continue to happen in coming years.
“Updating what’s in the memory is essential for spacecraft safety and for extending the mission,” said MRO Project Manager Dan Johnston at NASA’s Jet Propulsion Laboratory, Pasadena, California.
To update the location tables, engineers will rewrite the entire content of the nonvolatile memory on the spacecraft. The orbiter has two identical computers for redundancy, with only one of them active at a time. Each computer has its own nonvolatile memory unavailable to the other, so the rewrite needs to be done twice. The “Side B” computer has been active since an unplanned side swap in April 2015. The plan is to rewrite that computer’s nonvolatile memory starting on Nov. 2. The procedure for “Side A” will follow in early 2016.
The contents of each computer’s 256 megabytes of nonvolatile memory include backup copies of vital computer-operation files. “It’s the fundamental operating system of the spacecraft. That’s what adds risk,” Johnston said. “Just like with your home computer: If you mess with the operating system, the computer won’t work.”
Since MRO launched, the mission team has rewritten the nonvolatile memory just once, in 2009. The Side B rewrite next week will follow procedures similar to those used successfully in 2009, but with an added safeguard. After a partial rewrite, an intentional reboot will be commanded, to confirm that the newly recorded information is usable. If it is not, sufficient information from the 2009 rewrite would still be still available as backup for a successful reboot. After confirmation that the partial rewrite is successful, the rest of the memory contents will be replaced.
Though it is already in its fourth mission extension, MRO could remain a cornerstone of NASA’s Mars Exploration Program fleet for years to come. The longevity of the mission has given researchers tools to study seasonal and longer-term changes on Mars, including recently discovered seasonal activity of salty liquid water. Among other current activities, the orbiter is examining possible landing sites for future missions to Mars and relaying communications to Earth from Mars rovers.
JPL, a division of the California Institute of Technology in Pasadena, manages the MRO Project for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems in Denver built the orbiter and supports its operations. For more information about MRO, visit: http://www.nasa.gov/mor and http://mars.nasa.gov/mro and http://mars.nasa.gov/mroMission Status Report
- Rover examines geological contact zone near ‘Marias Pass’
- Silica-rich rocks identified nearby with laser-firing instrument
- Test of rover’s drill prepares for next use on Mars rock
Approaching the third anniversary of its landing on Mars, NASA’s Curiosity Mars rover has found a target unlike anything it has studied before — bedrock with surprisingly high levels of silica. Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz.
This area lies just downhill from a geological contact zone the rover has been studying near “Marias Pass” on lower Mount Sharp.
In fact, the Curiosity team decided to back up the rover 46 meters (151 feet) from the geological contact zone to investigate the high-silica target dubbed “Elk.” The decision was made after they analyzed data from two instruments, the laser-firing Chemistry & Camera (ChemCam) and Dynamic Albedo of Neutrons (DAN), which showed higher amounts of silicon and hydrogen, respectively. High levels of silica in the rock could indicate ideal conditions for preserving ancient organic material, if present, so the science team wants to take a closer look.
“One never knows what to expect on Mars, but the Elk target was interesting enough to go back and investigate,” said Roger Wiens, the principal investigator of the ChemCam instrument from the Los Alamos National Laboratory in New Mexico. ChemCam is coming up on its 1,000th target, having already fired its laser more than 260,000 times since Curiosity landed on Mars Aug. 6, 2012, Universal Time (evening of Aug. 5, Pacific Time).
In other news, an engineering test on the rover’s sample-collecting drill on July 18 is aiding analysis of intermittent short circuits in the drill’s percussion mechanism, in preparation for using the drill in the area where the rover has been working for the past two months. The latest test did not result in any short circuits, so the team plans to continue with more tests, performed on the science targets themselves.
Before Curiosity began further investigating the high-silica area, it was busy scrutinizing the geological contact zone near Marias Pass, where a pale mudstone meets darker sandstone.
“We found an outcrop named Missoula where the two rock types came together, but it was quite small and close to the ground. We used the robotic arm to capture a dog’s-eye view with the MAHLI camera, getting our nose right in there,” said Ashwin Vasavada, the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. MAHLI is short for Mars Hand Lens Imager.
The rover had reached this area after a steep climbed a 20-foot (6-meter) hill. Near the top of the climb, the ChemCam instrument fired its laser at the target Elk, and took a spectral reading of its composition.
“ChemCam acts like eyes and ears of the rover for nearby objects,” said Wiens.
The rover had moved on before analyzing the Elk data, so the rover performed a U-turn to get more data. Upon its return, the rover was able to study a similar target, “Lamoose,” up close with the MAHLI camera and the arm-mounted Alpha Particle X-ray Spectrometer (APXS).
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission now is to look at successively higher layers of Mount Sharp.
The U.S. Department of Energy’s Los Alamos National Laboratory developed ChemCam in partnership with scientists and engineers funded by the French national space agency. Russia’s space agency provided Curiosity’s DAN instrument. JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA’s Science Mission Directorate in Washington.
Martian weather and soil conditions that NASA’s Curiosity rover has measured, together with a type of salt found in Martian soil, could put liquid brine in the soil at night.
Perchlorate identified in Martian soil by the Curiosity mission, and previously by NASA’s Phoenix Mars Lander mission, has properties of absorbing water vapor from the atmosphere and lowering the freezing temperature of water. This has been proposed for years as a mechanism for possible existence of transient liquid brines at higher latitudes on modern Mars, despite the Red Planet’s cold and dry conditions.
New calculations were based on more than a full Mars year of temperature and humidity measurements by Curiosity. They indicate that conditions at the rover’s near-equatorial location were favorable for small quantities of brine to form during some nights throughout the year, drying out again after sunrise. Conditions should be even more favorable at higher latitudes, where colder temperatures and more water vapor can result in higher relative humidity more often.
“Liquid water is a requirement for life as we know it, and a target for Mars exploration missions,” said the report’s lead author, Javier Martin-Torres of the Spanish Research Council, Spain, and Lulea University of Technology, Sweden, and a member of Curiosity’s science team. “Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes.”
- Conditions that might produce liquid brine in Martian soil extend closer to the equator than expected
- Perchlorate salt in soil can pull water molecules from the atmosphere and act as anti-freeze
- Presence of brine would not make Curiosity’s vicinity favorable for microbes
The weather data in the report published today in Nature Geosciences come from the Cuirosity’s Rover Environmental Monitoring Station (REMS), which was provided by Spain and includes a relative-humidity sensor and a ground-temperature sensor. NASA’s Mars Science Laboratory Project is using Curiosity to investigate both ancient and modern environmental conditions in Mars’ Gale Crater region. The report also draws on measurements of hydrogen in the ground by the rover’s Dynamic Albedo of Neutrons (DAN) instrument, from Russia.
“We have not detected brines, but calculating the possibility that they might exist in Gale Crater during some nights testifies to the value of the round-the-clock and year-round measurements REMS is providing,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, Pasadena, California, one of the new report’s co-authors.
Curiosity is the first mission to measure relative humidity in the Martian atmosphere close to the surface and ground temperature through all times of day and all seasons of the Martian year. Relative humidity depends on the temperature of the air, as well as the amount of water vapor in it. Curiosity’s measurements of relative humidity range from about five percent on summer afternoons to 100 percent on autumn and winter nights.
Air filling pores in the soil interacts with air just above the ground. When its relative humidity gets above a threshold level, salts can absorb enough water molecules to become dissolved in liquid, a process called deliquescence. Perchlorate salts are especially good at this. Since perchlorate has been identified both at near-polar and near-equatorial sites, it may be present in soils all over the planet.
Researchers using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter have in recent years documented numerous sites on Mars where dark flows appear and extend on slopes during warm seasons. These features are called recurring slope lineae, or RSL. A leading hypothesis for how they occur involves brines formed by deliquesence.
“Gale Crater is one of the least likely places on Mars to have conditions for brines to form, compared to sites at higher latitudes or with more shading. So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations, perhaps enough to explain RSL activity,” said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, Tucson, also a co-author of the new report.
In the 12 months following its August 2012 landing, Curiosity found evidence for ancient streambeds and a lakebed environment more than 3 billion years ago that offered conditions favorable for microbial life. Now, the rover is examining a layered mountain inside Gale Crater for evidence about how ancient environmental conditions evolved. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory and Mars Reconnaissance Projects for NASA’s Science Mission Directorate, Washington.
For more information about Curiosity, visit:
“NASA science activities have provided a wave of amazing findings related to water in recent years that inspire us to continue investigating our origins and the fascinating possibilities for other worlds, and life, in the universe,” said Ellen Stofan, chief scientist for the agency. “In our lifetime, we may very well finally answer whether we are alone in the solar system and beyond.”
Perhaps the most surprising water worlds are the five icy moons of Jupiter and Saturn that show strong evidence of oceans beneath their surfaces: Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn.
On Mars, NASA spacecraft have found clear evidence that the Red Planet had water on its surface for long periods in the distant past. NASA’s Curiosity Mars Rover discovered an ancient streambed that existed amidst conditions favorable for life as we know it.
Understanding the distribution of water in our solar system tells us a great deal about how the planets, moons, comets and other bodies formed 4.5 billion years ago from the disk of gas and dust that surrounded our sun. The space closer to the sun was hotter and drier than the space farther from the sun, which was cold enough for water to condense. The dividing line, called the “frost line,” sat around Jupiter’s present-day orbit. Even today, this is the approximate distance from the sun at which the ice on most comets begins to melt and become “active.” Their brilliant spray releases water ice, vapor, dust and other chemicals, which are thought to form the bedrock of most worlds of the frigid outer solar system.