Curiosity, Interrupted: Sun Makes Mars Go Dark
Since NASA's Mars Science Laboratory (MSL) rover Curiosity landed on the red planet, each sol (a Martian "day") of the mission sees a flood of new photographs from Aeolis Palus -- the plain inside Gale Crater where Curiosity landed on Aug. 5. In September 2012, mission controllers sent the command for Curiosity to flip open the dust cap in front of the robotic arm-mounted Mars Hand Lens Imager (MAHLI). Until that point, the semi-transparent dust cap only allowed MAHLI to make out fuzzy shapes -- although it did a great job imaging Curiosity's "head" and it is also famous for capturing Curiosity's first color photograph. But since the true clarity of MAHLI has been unleashed, we've been treated to some of the most high-resolution views of the rover, Martian landscape and, most importantly, we've seen exactly what MAHLI was designed to do: Look closely at Mars rocks and dirt, assembling geological evidence of potential past habitability of Mars.
The Business End
Curiosity is armed with 17 cameras and MAHLI is designed to capture close-up photos of geological samples and formations as the rover explores. MAHLI was designed and built by Malin Space Science Systems and is analogous to a geologist's hand lens -- only a lot more sophisticated. Its high-resolution system can focus and magnify objects as small as 12.5 micrometers (that's smaller than the width of a human hair!). This photograph captured by the rover's Mastcam shows the MAHLI lens (with dust cap in place) in the center of the end of Curiosity's instrument-laden robotic arm.
To aid its studies, MAHLI is equipped with four LEDs to light up the imager's samples.
The first photograph to be returned from MAHLI without the dust cover in place was received on Sol 33 (Sept. 8) of Curiosity's mission. Shown here is a view of the ground immediately in front of the rover. Although this photo was a test, mission scientists were able to do a very preliminary study of the large "pebble" at the bottom of the picture: "Notice that the ground immediately around that pebble has less dust visible (more gravel exposed) than in other parts of the image. The presence of the pebble may have affected the wind in a way that preferentially removes dust from the surface around it," they wrote.
How Did Lincoln Help MAHLI?
On Sol 34 (Sept. 9), MAHLI was aimed at Curiosity's calibration target. This target is intended to color balance the instrument and provide a "standard" for mission scientists to refer to. The 1909 Lincoln penny was provided by MAHLI's principal investigatory Ken Edgett. Using a penny as a calibration target is a nod to geologists' tradition of placing a coin or some other object of known scale as a size reference in close-up photographs of rocks, says the MSL mission site.
Although MAHLI will be used to examine microscopic scales, it is showing its prowess at generating some spectacular high-definition views of the rover. Shown here is a mosaic of Curiosity's three left-side dusty wheels.
Hazard Avoidance Cameras
Hazard Avoidance Cameras, or Hazcams, have become "standard issue" for the last three rovers to land on Mars. Mounted on the front and back of rovers Opportunity, Spirit and Curiosity, these small cameras provide invaluable information about the terrain and potential hazards surrounding the rovers. These cameras are not scientific cameras -- they are engineering cameras. Shown here, MAHLI has imaged the four front Hazcams on Curiosity. Interestingly, it was these cameras who returned Curiosity's first dusty image after touch down in August.
Using the flexibility of the robotic arm, MAHLI was able to check the underside of Curiosity. As the camera can focus on objects from 0.8 inch (2.1 centimeters) to infinity, MAHLI has incredible versatility allowing mission controllers to focus on the very small features of Mars to checking the health of the rover to viewing the impressive vistas beyond.
In October 2012, the Internet was abuzz with speculation about a "mystery object" lying beneath the rover during digging operations at "Rocknest." Sadly, after studying the translucent object, mission scientists deduced that it wasn't anything native to the alien environment, it was actually a piece of plastic that had fallen from Curiosity. Yes, Curiosity is littering the red planet.
The MAHLI camera was very attentive while Curiosity dug trenches in the Mars soil at "Rocknest."
In early 2013, MAHLI snapped another curious photo. This time, after driving to a rocky outcrop at a location dubbed "Yellowknife," the camera picked out what appeared to be some kind of organic-looking object embedded in the rock. Nope, it's not a Mars "flower" -- more likely it's a concentration of minerals.
In what has become an iconic photo of Curiosity, MAHLI was commanded to capture dozens of high-resolution pictures of the rover. Like an "arms length" shot you may have in your Facebook profile, Curiosity did the same, composing a mosaic of pics taken with its outstretched robotic arm.
Curiosity Cleans Up!
The Mars rover isn't only a scientific superstar, it also has a talent for cleaning. This circular pattern on a Mars rock was brushed aside by Curiosity's Dust Removal Tool (DRT), helping the rover carry out analysis of the rock surface beneath the layer of dirt.
NASA has stopped sending commands to Mars rover Curiosity and will soon follow suit for rover Opportunity, Odyssey and the Mars Reconnaissance Orbiter (MRO). But don’t worry, government cutbacks haven’t severed interplanetary communications, you can blame the sun.
Once every 26 months the orbits of Earth and Mars align in such a way that our nearest star physically gets in the way of our line of sight. Known as a “Mars solar conjunction,” from our point of view, the red planet almost passes directly behind the solar disk. This means, inevitably, communications between the planets are severely disrupted.
Curiosity mission managers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., suspended communications with the one-ton robot yesterday (April 4) so to avoid any corruption of data. They won’t recommence transmissions until May 1.
The sun’s lower atmosphere (the corona) is buzzing with highly charged particles, causing interference with radio communications that pass through it. Also, each conjunction is different, depending on orbital inclination and solar activity. The sun is currently undergoing “solar maximum” — peak activity for its approximate 11-year cycle. This conjunction will see Mars close in on the solar limb by only 0.4 degree on April 17 — a maximum period for interference.
Although receiving data from the rover isn’t too much of a problem (blocks of missing data can be requested again later), sending commands, only for the data to become corrupted on the way to Mars, could be a serious issue for the health of the mission.
Commands to the NASA orbiters will also be suspended from April 9 to 26. The MRO has been switched to a “record only” mode whereas the veteran Odyssey will continue to transmit throughout the conjunction — although NASA is expecting the inevitable data drop-outs particularly around April 17. Operations of the European Mars Express satellite, which has been orbiting Mars since 2003, will also be affected.
“For the entire conjunction period, we’ll just be storing data on board (the Mars Reconnaissance Orbiter),” said JPL’s Reid Thomas, MRO Deputy Mission Manager. The orbiter is expected to accumulate 40 gigabits of science data from its own instruments and 12 gigabits of data from Curiosity, which will all be downloaded to Earth around May 1.
“This is our sixth conjunction for Odyssey,” said Chris Potts, Odyssey mission manager at JPL. “We have plenty of useful experience dealing with them, though each conjunction is a little different.” Odyssey has been orbiting Mars since 2001.
“The biggest difference for this 2013 conjunction is having Curiosity on Mars,” added Potts.
Although NASA won’t be transmitting, Curiosity will be sending regular “beeps” to Earth to reassure us that it’s OK. “We will maintain visibility of rover status two ways,” said Torsten Zorn, conjunction planning leader for Curiosity’s JPL engineering operations team. “First, Curiosity will be sending daily beeps directly to Earth. Our second line of visibility is in the Odyssey relays.”
Curiosity landed inside Gale Crater on Aug. 5, 2012, and has already made groundbreaking (literally) progress in the hunt of evidence for past (and present) habitability of the red planet. This communications blackout is the first time Curiosity will be alone.
Image: Diagram showing the configuration of a Mars solar conjunction. Credit: NASA/JPL-Caltech