By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at https://beacon.jpl.nasa.gov/.

Viking Stereo Viewer — Photograph Number 324-1954

This interactive computer-based stereo viewing system was used to analyze Mars topography images generated by the cameras on NASA’s Viking 1 Mars lander. Two 17-inch video monitors faced a scanning stereoscope mounted between them on a table. Left and right lander camera image data were sent to the left and right monitors. Panning controls on the stereoscope helped align one image with the other to create a stereo image, 640 by 512 pixels in size. A mouse was used for finely controlled rotation of the monitors. An article about the system described a prototype mouse, used before this photo was taken in 1976. “The track ball is a baseball-sized sphere protruding from the top of a retaining box and capable of being rotated freely and indefinitely about its center …”

The resulting images could be displayed on additional monitors and were used to create contour maps and other images that aided lander surface operations. The system was developed by Stanford University and NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

By John Callas

Below are remarks made by Mars Exploration Rover Project Manager John Callas at the NASA Jet Propulsion Laboratory’s Spirit Celebration on July 19, 2011.

Artist’s concept of NASA’s Mars Exploration Rover. Image credit: NASA/JPL-Caltech

“We are here today to celebrate this great triumph of exploration, the incredible mission of this Mars rover. As bittersweet as the conclusion of Spirit’s time on Mars is for each of us, our job was to get to this day. To wear these rovers out, to leave behind no unutilized capability on the surface of Mars. For Spirit, we have done that.

What is truly remarkable is how much durability and capability Spirit had. These rovers were designed for only 90 days on the surface and one kilometer of driving distance. On her last day, Spirit had operated for 2210 Martian days, drove over 7730 meters and returned over 124 thousand images.

But it is not how long this rover lasted or how far she had driven, but how much exploration and scientific discovery she has accomplished. Spirit escaped the volcanic plains of Gusev Crater, mountaineer-ed up the Columbia Hills, survived three cold, dark Martian winters and two rover-killing dust storms, and surmounted debilitating hardware malfunctions. But out of this adversity, she made the most striking scientific discoveries that have forever changed our understanding of the Red Planet.

With the rovers originally designed only for a limited stay in the relatively comfortable environment of the Martian summer, the many years of extended operation meant these vehicles operate most of their time in the extreme environments of frigid temperatures and dark skies, well outside of their original design limits. The longevity and productivity of these rovers under such severe environmental conditions speak to the talent and dedication of the people, who designed, built, tested and operated these vehicles.

Spirit’s discoveries have changed our understanding of the Red Planet. We know now that Mars was not always a cold, dry and barren planet. That at one time liquid water flowed on it surface, sustained by a thicker atmosphere and warmer temperatures. At least, kilometer-scale lakes persisted in places. And that there were even sources of energy, hydrothermal systems, that could have supported life in this earlier habitable world.

We can’t do the impossible, make these machines operate forever. But, we have come as close to that as humans can. Spirit’s very accomplished exploration of Mars has rewritten the textbooks about the planet. Further, this rover has changed our understanding of ourselves and of our place in the Universe and approached questions of, are we alone and what is the future of this world?

But, beyond all the exploration and scientific discovery, Spirit has also given us a great intangible. Mars is no longer this distant, alien world. It is now our neighborhood. We go to work on Mars everyday.

But, let’s also remember that Spirit’s great accomplishments did not come at the expense of some vanquished foe or by outscoring some opponent. Spirit did this, we did this - to explore, to discover, to learn - for the benefit of all humankind. In that respect, these rovers represent the highest aspiration of our species.

Well done little rover. Sleep in peace. And, congratulations to you all. Thank you very much.”

By John Callas

Mars Exploration Rover Project Manager John Callas sent this letter to his team shortly after the final command was sent to the Mars rover Sprit, which operated on the surface of Mars for more than six years and made numerous scientific discoveries.

Artist’s concept of NASA’s Mars Exploration Rover. Image credit: NASA/JPL-Caltech

Dear Team,

Last night, just after midnight, the last recovery command was sent to Spirit. It would be an understatement to say that this was a significant moment. Since the last communication from Spirit on March 22, 2010 (Sol 2210), as she entered her fourth Martian winter, nothing has been heard from her. There is a continued silence from the Gusev site on Mars.

We must remember that we are at this point because we did what we said we would do, to wear the rovers out exploring. For Spirit, we have done that, and then some.

Spirit was designed as a 3-month mission with a kilometer of traverse capability. The rover lasted over 6 years and drove over 7.7 kilometers [4.8 miles] and returned over 124,000 images. Importantly, it is not how long the rover lasted, but how much exploration and discovery Spirit has done.

This is a rover that faced continuous challenges and had to fight for every discovery. Nothing came easy for Spirit. When she landed, she had the Sol 18 flash memory anomaly that threatened her survival. Scientifically, Mars threw a curveball. What was to be a site for lakebed sediments at Gusev, turned out to be a plain of volcanic material as far as the rover eye could see. So Spirit dashed across the plains in an attempt to reach the distant Columbia Hills, believed to be more ancient than the plains.

Exceeding her prime mission duration and odometry, Spirit scrambled up the Columbia Hills, performing Martian mountaineering, something she was never designed to do. There Spirit found her first evidence of water-altered rocks, and later, carbonates.

The environment for Spirit was always harsher than for Opportunity. The winters are deeper and darker. And Gusev is much dustier than Meridiani. Spirit had an ever-increasing accumulation of dust on her arrays. Each winter became harder than the last.

It was after her second Earth year on Mars when Spirit descended down the other side of the Columbia Hills that she experienced the first major failure of the mission, her right-front wheel failed. Spirit had to re-learn to drive with just five wheels, driving mostly backwards dragging her failed wheel. It is out of this failure that Spirit made one of the most significant discoveries of the mission. Out of lemons, Spirit made lemonade.

Each winter was hard for Spirit. But with ever-accumulating dust and the failed wheel that limited the maximum achievable slope, Spirit had no options for surviving the looming fourth winter. So we made a hard push toward some high-value science to the south. But the first path there, up onto Home Plate, was not passable. So we went for Plan B, around to the northeast of Home Plate. That too was not passable and the clock was ticking. We were left with our last choice, the longest and most risky, to head around Home Plate to the west.

It was along this path that Spirit, with her degraded 5-wheel driving, broke through an unseen hazard and became embedded in unconsolidated fine material that trapped the rover. Even this unfortunate event turned into another exciting scientific discovery. We conducted a very ambitious extrication effort, but the extrication on Mars ran out of time with the fourth winter and was further complicated by another wheel failure.

With no favorable tilt and more dust on the arrays, Spirit likely ran out of energy and succumbed to the cold temperatures during the fourth winter. There was a plausible expectation that the rover might survive the cold and wake up in the spring, but a lack of response from the rover after more than 1,200 recovery commands were sent to rouse her indicates that Spirit will sleep forever.

But let’s remember the adventure we have had. Spirit has climbed mountains, survived rover-killing dust storms, rode out three cold, dark winters and made some of the most spectacular discoveries on Mars. She has told us that Mars was once like Earth. There was water and hot springs, the conditions that could have supported life. She has given us a foundation to further explore the Red Planet and to understand ourselves and our place in the universe.

But in addition to all the scientific discoveries Spirit has given us in her long, productive rover life, she has also given us a great intangible. Mars is no longer a strange, distant and unknown place. Mars is now our neighborhood. And we all go to work on Mars every day. Thank you, Spirit. Well done, little rover.

And to all of you, well done, too.

Sincerely,
John

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By Erik Conway, writing for My Big Fat Planet

Mars has been a grand scientific mystery ever since the first modern images were beamed back from the Mariner 4 spacecraft in 1965. Those snapshots showed a moon-like, cratered surface — not what we expected. Scientists had assumed that Mars would have an Earth-like atmosphere, composed mainly of nitrogen and with traces of carbon dioxide and water vapor. What they found instead was a cold desert world, one that possessed a thin wisp of an atmosphere containing only carbon dioxide.

Subsequent missions to the Red Planet detected tiny amounts of water vapor in Mars’ atmosphere, and better images began to unveil what looked like river channels and deltas on the surface. Indeed, spacecraft launched in the late 1990s and 2000s found water on Mars in the form of ice, bound into the planet’s soil and in great underground deposits. Water used to flow on the surface of Mars. But how? And where did it all go?

At first sight, the facts defy logic. According to astronomers, the sun used to be dimmer (i.e. colder) than it is now, meaning that Mars (and Earth) should have been colder in the past, not warmer. But observations tell us that it was clearly warmer and wetter on Mars in the past — not colder and more frozen. How did Mars buck the trend and stay toasty in the past? The most likely answer is that it used to have some sort of “super greenhouse effect” going on, the like of which we see on Venus. On Venus, the thick carbon-dioxide-based atmosphere traps the sun’s heat, resulting in surface temperatures that are hot enough to melt lead. Scientists think that early Mars also had a thick, carbon-dioxide-rich atmosphere that provided warming.

That said, in a recent talk at the American Geophysical Union conference in San Francisco, Mars specialist Bruce Jakosky of the University of Colorado pointed out that heat-trapping carbon dioxide alone would not have been sufficient to make Mars warm enough and wet enough to match our observations. Carbon dioxide’s ability to trap heat would have at some point “saturated”, or maxed out. Other greenhouse gases, like methane or ammonia, might have helped trap more heat near the surface of Mars — but they would not have been sufficient either because the sun’s ultraviolet radiation would have destroyed them far too quickly. Ergo, some sort of ultraviolet-absorbing layer high in Mars’ atmosphere would have been needed to help trap the heat. (The Earth’s ozone layer, which dates back to somewhere between 2 and 2.7 billion years ago, performs this service for us now.)

There is, as yet, no evidence of the necessary chemicals on Mars to do this. Jakosky didn’t draw any firm conclusions about how the warmer Mars could have existed. But he did lay out possible future investigations that might help uncover parts of this mystery a little more clearly. One of those includes the MAVEN mission to Mars, scheduled for launch in 2013, which will study how Mars’ atmosphere and climate has changed over time.

As Jakosky has said, in some ways, Mars is a very Earth-like planet. By looking at conditions on other worlds, we can gain insights into how, and why, our own climate is changing here on planet Earth.

You can read more about the Mars Science Laboratory rover here. Scheduled for launch in the fall of 2011, the Curiosity rover will help determine whether Mars has in the past, or does today, harbor life.

This post was written for “My Big Fat Planet,” a blog hosted by Amber Jenkins on NASA’s Global Climate Change site.