Archive for the ‘Mars’ Category

Habitability, Taphonomy, and Curiosity’s Hunt for Organic Carbon

Tuesday, December 24th, 2013

By John Grotzinger
This blog entry from John Grotzinger, the project scientist for NASA’s Curiosity Mars rover, was originally prepared for use by the Planetary Society and explains the importance of some of the rover’s findings.

Curiosity Selfie

This self-portrait of NASA’s Mars rover Curiosity combines dozens of exposures taken by the rover’s Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity’s work on Mars (Feb. 3, 2013), plus three exposures taken during Sol 270 (May 10, 2013)
› Full image and caption

It was fun for me to catch up with Emily Lakdawalla of the Planetary Society at the American Geophysical Union meeting, and to discuss our new Curiosity mission results. They focus on the discovery of an ancient habitable environment; we are now transitioning to the focused search for organic carbon. What’s great about Emily’s blog is that with her strong science background she is able to take complex mission results and translate these into something that can reach a broader and more diverse audience. I’ll try to do the same here.

Since we first reported our results on March 12, 2013, from drilling in Yellowknife Bay it has been my experience that lots of people ask questions about how the Curiosity mission, and future missions, will forge ahead to begin with looking for evidence of past life on Mars. There is nothing simple or straightforward about looking for life, so I was pleased to have the chance to address some of the questions and challenges that we find ourselves most frequently discussing with friends and colleagues. The Planetary Society’s blog is an ideal place to take the time to delve into this.

I also need to state at the outset that what you’ll read below is my opinion, as Curiosity science team member and Earth geobiologist, and not necessarily as its Project Scientist. And I have only worked on Mars science for a decade. However, I can say that many other members of the Curiosity team share this opinion, generated from their own experiences similar to mine, and it was easy for us to adopt these ideas to apply to our future mission. To a large extent, this opinion is shaped by our experience of having spent decades trying to explore the early record of life on Earth. As veterans of the Mars Exploration Rover and Curiosity missions, we have learned that while Mars has significant differences from Earth, it also has some surprising similarities that could be important in the search for evidence of ancient Martian life - a “paleobiosphere,” if you will. The bottom line is that even for Earth, a planet that teems with life, the search for ancient life is always difficult and often frustrating. It takes a while to succeed. I’ll try to explain why later on.

So here goes….

The Dec. 9, 2013, publication of the Curiosity team’s six papers in Science provides the basis for understanding a potentially habitable environment on ancient Mars. The search for habitable environments motivated building the rover, and to that end the Curiosity mission has accomplished its principal objective. This naturally leads to the questions of what’s next, and how we go about exploring for organic carbon?

To better understand where we’re coming from, it helps to break down these questions and analyze them separately. With future advocacy of missions to Mars so uncertain, and with difficult-to-grasp mission objectives located between “the search for water” (everyone got that) and “the search for life” (everyone wants NASA to get on with it), the “search for habitability” and the “search for carbon” are important intermediate steps. By focusing on them scientists can identify specific materials to study with more sophisticated future missions and instruments, or to select for sample return, or to be the target of life detection experiments.

Note: You can get access to all six of these Science papers here or here. The latter site also has the papers we published back in September. Science has a policy that allows us to post a “referrer link” to our home websites. This redirects the query to AAAS, where the paper can be downloaded without cost.

Habitability

Let’s start with “habitability.” We reported the discovery of an ancient lake, and one that formed clay minerals. The presence of clays represents more benign environmental conditions than the acid sulfates found by Spirit and Opportunity. However, clays are not the only thing needed to demonstrate habitability. The bar is high: In brief, a mission needs to demonstrate the presence of water, key elements regarded as the building blocks of life (including carbon), and a source of energy. And you need to find them all together, and at the same instant in geologic time. In turn, each one of these must be characterized further to qualify an environment as having been habitable. Finally, it’s never black and white; understanding habitability is part of a broad continuum of environmental assessment, which is why orbiters and earlier rovers and landers are important assets in this process as well.

It is also important to define what group of organisms is being imagined to have inhabited the environments - their requirements will vary. Single-celled microorganisms are a great place to start based on our understanding of the early evolution of life on Earth, which was dominated by microbes for at least the first two billion years of the planet’s history. More specifically, the Curiosity team has been focusing on the conditions of habitability relevant to “chemolithotrophs,” a group of microbes that feeds on chemical energy available in rocks.

Water.

The water of a habitable environment should be relatively fresh, or at least not contain so much salt that the relative abundance of water is so low (what chemists call “water activity”) that the osmotic pressure on cells would cause them to collapse. My favorite analog here is honey. Yes, it’s an aqueous environment but no, it’s not habitable: The sugar content is so high that microbes can’t live in it. This is why honey doesn’t spoil when not refrigerated. Salt serves the same role as sugar; too much salt inhibits life. Acidity is also important, although microbes have been shown to tolerate an extraordinary range of pH, including the very lowest values encountered in natural environments on Earth. However, more moderate pH favors a greater diversity of microorganisms, and thus more options to explore for emerging life forms. Finally, the water needs to last a long time on the surface; the longer, the better. A flow of water emerging on the surface of Mars from an underground source and boiling off in the presence of Mars’ modern low atmospheric pressure is not a good scenario for life. A stable source, such as a very ancient lake, with associated streams, and water flowing through the ground beneath it, is much better. We envision for the lake/stream/groundwater system that Curiosity discovered at Yellowknife Bay that the water could have existed for millions of years potentially. But even shorter periods are viable - the qualitative point here is that the rocks at Yellowknife Bay record more than a one-time event.

Key building blocks of life.

A conventional list of key elements for life will include “CHNOPS” - carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Previous orbiter and landed missions have provided ample evidence for H, O, and S via observations of sulfate and clay minerals, and P was measured by earlier rovers and landers. Curiosity has done the same. The tricky stuff is N and C and, along with P, they must all be “bioavailable,” which means to say they cannot be bound tightly within mineral structures that water and microbial chemical processes could not unlock. Ideally, we are looking for concentrated nitrogen- and phosphorous-bearing sedimentary rocks that would prove these elements were actually dissolved in the past water at some point, and therefore could have been available to enable microorganism metabolism. But in the interim Curiosity has been able to measure N as a volatile compound via pyrolysis (heating up rock powder in the SAM instrument), and P is observed in APXS data. We feel confident that N was available in the ancient environment, however we must infer that P was as well. Two of the Science papers, Grotzinger et al. and Ming et al., discuss this further.

Carbon is the elephant in the room. We’ll discuss organic carbon further below, but here it’s important to make one very important point: Organic carbon in rocks is not a hard-line requirement for habitability, since chemoautotrophs can make the organics they need to build cellular structures from metabolizing carbon dioxide (CO2). These organisms take up inorganic carbon as CO2 dissolved in water to build cellular structures. Organic carbon could serve as fuel if it was first oxidized to CO2, or could be used directly for biomass, or could be part of waste products. As applied to Mars it is therefore attractive to appeal directly to CO2, presumed to have been abundant in its early atmosphere. Curiosity does indeed see substantial carbon generated from the ancient lake deposits we drilled. The CO2 that was measured is consistent with some small amount of mineral carbon present in those lake mudstones. These minerals would represent CO2 in the ancient aqueous environment. Furthermore, it is possible that Martian organic sources have been mixed with inorganic sources of carbon in the mudstone; however, any organic contributions from the mudstone would be mixed with Earth-derived sources during analysis (see Ming et al. paper).

Energy.

All organisms also require fuel to live and reproduce. Here it is essential to know which kind of microorganism we’re talking about, since there are myriad ways for them to harvest energy from the environment. Chemolithotrophs derive energy from chemical reactions, for example by oxidizing reduced chemical species like hydrogen sulfide or ferrous iron. That’s why Curiosity’s discovery of pyrite, pyrrhotite, and magnetite are so important (see Vaniman et al. and Ming et al. papers). They are all more chemically reduced than their counterparts discovered during earlier missions to Mars (for example, sulfate and hematite). Chemolithotrophic microbes, if they had been present on Mars at the time of this ancient environment, would have been able to tap the energy in these reduced chemicals (such as hydrogen sulfide, or reduced iron) to fuel their metabolism. If you are interested in more detail regarding these kinds of microbial processes I can strongly recommend Nealson and Conrad (2000) for a very readable summary of the subject.

The next section describes where I think we’re headed in the future. We’ll continue to explore for aqueous, habitable environments at Mt. Sharp, and along the way to Mt. Sharp. And if we discover any, they will serve as the starting point for seeing if any organic carbon is preserved and, if so, how it became preserved.

Taphonomy

Now there’s a ten-dollar word. Taphonomy is the term paleontologists use to describe how organisms become fossilized. It deals with the processes of preservation. Investigations of organic compounds fit neatly in that category. We do not have to presume that organic compounds are of biologic origin. In fact, in studies of the Earth’s early record of life, we must also presume that any organic materials we find may be of inorganic origin - they may have nothing to do with biology. Scientific research will aim to demonstrate as conclusively as possible that the materials of interest were biogenic in origin. For Earth rocks that are billions of years old, it’s rare to find a truly compelling claim of ancient biogenic carbon. Here’s why.

On a planet that teems with life, one would presume these discoveries would be ordinary. But they aren’t, and that’s why fossils of almost any type, including organic compounds (so-called “chemofossils”), are so cool - it’s because they are rare. That’s also why taphonomy emerged as an important field of study. We need to understand how biologic materials become recorded in Earth’s rock record. It’s important in understanding modes of organism decomposition, to interpret ancient environmental conditions, and in reconstructing ancient ecosystems. But there also is one other reason that is particularly relevant for early Earth, and even more so for Mars: If you want to find something significant, you have to know where to look.

To explore for organics on Mars, three things have to go right. First, you need to have an enrichment of organics in the primary environment where organic molecules accumulate, which is large enough so that your instrument could detect them. Second, the organics have to survive the degrading effects associated with the conversion of sediment to rock. Third, they must survive further degradation caused by exposure of rock to cosmic radiation at Mars’ surface. Even if organics were once present in Martian sediment, conversion to rock and exposure to cosmic radiation may degrade the organics to the point where they can’t be detected.

Organics degrade in two main ways. The first is that during the conversion of sediment to rock, organics may be chemically altered. This generally happens when layers of sediment are deposited one on top of the other, burying earlier-deposited layers. As this happens, the buried sediment is exposed to fluids that drive lithification - the process that converts sediment to rock. Sediments get turned into rocks when water circulates through their pores, precipitating minerals along the linings of the pores. After a while the sediment will no longer feel squishy and it becomes rigid - lithified.

During the process of lithification, a large amount of water may circulate through the rock. It can amount to hundreds, if not thousands, of times the volume of the pore space within the rock. With so much water passing through, often carrying other chemicals with it, any organics that come into contact with the water may be broken down. Chemically, this occurs because organics are reduced substances and many chemicals dissolved in water are oxidizing. Those two chemical states don’t sit well together, and this tends to drive chemical reactions. Simply put, organics could be broken down to the point where the originally organic carbon is converted into inorganic carbon dioxide, a gas that can easily escape the lithifying sediment. Water on Mars may be a good thing for habitability but it can, paradoxically, negatively affect the preservation of organics.

Now, if any organics manage to escape this first step in degradation, then they are still subject to further degradation when the rock is exhumed and exposed to the surface of Mars. There it will be bombarded by cosmic radiation. I won’t go into the details here, but that is also bad news for organics because the radiation tends to break apart organic molecules through a process called ionization. The upper few meters of a rock unit is the most susceptible; below that the radiation effect rapidly dies away. Given enough time the organics could be significantly degraded.

The Hassler et al. paper just published in Science reports that the surface radiation dose measured by Curiosity could, in 650 million years, reduce the concentration of small organic molecules, such as amino acids, by a factor of 1000, all other factors being equal. That’s a big effect - and that’s why we were so excited as a team when we figured out how to measure the cosmogenic exposure age of rocks we drilled (see Emily’s blog and the Farley et al. paper). This gives us a dependable way to preferentially explore for those rocks that have been exposed for the shortest period of time. Furthermore, it is unlikely that organics would be completely eliminated due to radiation effects and the proof of this is that a certain class of meteorites - the carbonaceous chondrites - have been exposed to radiation in space for billions of years and yet still retain complex organics. This provides hope that at least some types of organics should be preserved on Mars.

Being able to account for the radiation history of rocks that Curiosity might drill is a very big step forward for us in the search for organic molecules. It is a big step forward in learning how to explore for past life on Mars (if it ever existed there). Now we have the right tools to guide the search for rocks that might make the best targets for drilling. Coupled with our other instruments that measure the chemistry and mineralogy of the rocks, to help select those that might have seen the least alteration of organics during burial, we have a pretty good sense of what we need to do next. That’s because we have been through this before on Earth.

Magic Minerals

Over the years Emily has written many blogs dedicated to the discovery of interesting minerals on Mars. There are many reasons for this, but I’ll suggest one more that may grow in importance in years to come.

Believe it or not, the story starts with none other than Charles Darwin. In pondering the seemingly instantaneous appearance of fossils representing complex and highly differentiated organisms in Cambrian-age rocks (about 500 million years ago), Darwin recognized this as a major challenge to his view of evolution. He explained the sudden appearance of fossils in the record by postulating that Cambrian organisms with no known antecedents could be explained by “record failure” - for some unknown reason, older rocks simply didn’t record the emergence and evolution of life’s beginning. Conditions weren’t suitable to preserve organisms as fossils.

Most of that story goes on in the direction of evolutionary biology, and we’ll skip that, rather focusing instead on learning more about taphonomy. What is important for Mars was the discovery of minerals that could preserve evidence of early microorganisms on Earth. (For a good read on Precambrian paleobiology, try Andy Knoll’s “Life on a Young Planet: The First Three Billion Years of Evolution on Earth.”)

We now know that pre-Cambrian time represents about 4 billion years of Earth’s history, compared to the 540 million years represented by Cambrian and younger rocks that Darwin had studied. (See Emily’s blog on the Geologic time scale.) We also know now that the oldest fossil microbes on Earth are about 3.5 billion years old, and that in between there is a compelling, but very sparse record of the fossil organisms that Darwin had anticipated. However, what’s even more remarkable is that it took 100 years to prove this. And this was with hundreds, maybe thousands, of geologists scouring the far corners of the Earth looking for evidence.

The big breakthrough came in 1954 with the discovery of the “Gunflint microbiota” along the shores of Lake Superior in southern Canada. A University of Wisconsin economic geologist, Stanley Tyler, discovered microscopic threads of what we now understand to be fossil bacteria in a kind of rock called “chert”. Chert is a microcrystalline material formed of the mineral quartz, or silicon dioxide, which precipitates very early in waters that contain microbial colonies. It forms so early that it turns the sediment almost instantly into rock, and any microbes become entombed in a mineral so stable it resists all subsequent exposure to water, and the oxidizing chemicals dissolved in water, for billions of years.

As it turned out, this was the Rosetta stone that helped decipher the code to the field of pre-Cambrian paleontology. It took almost 10 years for the discovery to be fully appreciated (the initial report in Science was viewed with much skepticism), but once it was confirmed, in the mid-1960s, the field exploded. Once geologists and paleontologists knew what to search for, they were off to the races. Since that initial discovery, other magic minerals have been found that preserve ancient microbes, sometimes with spectacular fidelity. But chert is still the mineral of choice, and I never pass by it in the field without collecting some.

We don’t know yet what magic minerals exist on Mars that could have trapped and preserved organics. Clays and sulfates hold promise, and that’s why we’re so interested in them. Silica, perhaps similar to terrestrial chert, has been observed from orbit at a few places on Mars, and in Spirit rover data from Gusev crater. The great thing about Gale crater as a landing site is that we have so many choices in this trial-and-error game of locating a mineral that can preserve organic carbon.

The figure below provides some sense of the impact of this discovery. It is modified from a similar figure published in a very nice summary by Bill Schopf, a Professor of Paleontology at UCLA. Bill also was a very early participant in this race for discovery and has made a number of very significant contributions to the field.

chart

In studying Mars, the importance of this lesson in the search for life preserved in the ancient rock record of Earth cannot be overstated. Curiosity’s discovery of a very Earth-like ancient habitable environment underscores this point. With only one or two rovers every decade, we need to have a search paradigm: something to guide our exploration, something to explain our inevitable failures. If life ever evolved on Mars, we need to have a strategy to find it. That strategy begins with the search for organics, and regardless of their origin - abiotic or biotic, indigenous to Mars or not - they are important tracers for something more significant. Curiosity cannot see microfossils, but it can detect organic compounds. And just as with microfossils on Earth, we first have to learn where organics on Mars might be preserved. So that’s what we’re going to try and do.


Mariner 4 Taught Us to See

Friday, August 30th, 2013
The first 'image' of Mars from NASA's Mariner 4
Mission team members for NASA’s Mariner 4 spacecraft, incredibly anxious to see the first up-close photograph of Mars, devised a way to see the image before it made its way to Earth by color-coding binary code on strips of ticker tape. The resulting collage became known as “the first image of Mars.” Image credit: NASA/JPL-Caltech

In today’s universe, it seems unimaginable that a planetary spacecraft would leave the comfort of its terrestrial perch without some kind of imaging system on board. But in the early 1960s, as NASA’s Jet Propulsion Laboratory was reveling in the success of its first planetary mission to Venus and setting its sights on Mars — a destination whose challenges would unfurl themselves much more readily than they had with Venus — for some scientists, the question of camera or none was still just that, a question.

Bud Schurmeier, project manager for NASA’s Ranger missions, a few years ago recalled, “There were a lot of scientists who said, ‘Pictures, that’s not science. That’s just public information.’ Over the years, that attitude has changed so markedly, and so much information has been obtained just from the photographs.”

The recent passing of former JPL Director and career-long planetary imaging advocate Bruce C. Murray, 81, is a reminder of how different our understanding of the planets — and our appreciation of them — would be without space-based cameras.

This truth was evident as early as 1965, when NASA’s Mariner 4, carrying an imaging system designed by a young Murray and his colleagues, arrived at Mars. It marked the world’s first encounter with the Red Planet, a remarkable achievement in itself. But for an anxious press, public and mission team, the Holy Grail lay in catching that first glimpse of Mars up-close.

It was a waiting game that was too much for some. For everyone, in fact:


This is a clip from the JPL-produced film The Changing Face of Mars about the laboratory’s early attempts to explore the Red Planet. Credit: NASA’s Jet Propulsion Laboratory

What resulted became known as “The first image of Mars.” And in many ways it symbolizes — more than any of the actual 22 photographs captured by Mariner 4 — how significant this opportunity to truly “see” Mars had been.

Now, nearly 50 years after Mariner 4’s arrival at Mars, imaging systems are an integral piece of our quest to understand the planets and the universe beyond, playing key roles in scientific investigations, spacecraft navigation and public support for missions. It’s because of that first image that we can now look at that red dot in the night sky and picture what has become our new reality of Mars:

Curiosity's first billion pixel panorama
This image is a portion of a billion-pixel panorama from NASA’s Mars rover Curiosity that combines 900 images taken by the rover from Oct. 5 through Nov. 16, 2012 from its “Rocknest” site on Mars. Image credit: NASA/JPL-Caltech
› Explore the full panorama

Mission Control to Mars: Launching the Next Mars Rover

Monday, November 28th, 2011

By Rob Manning

In the wee morning hours of Nov. 26, 2011, scientists and engineers gathered in the mission control room at NASA’s Jet Propulsion Laboratory to help launch the next Mars rover, Curiosity. The mission’s chief engineer, Rob Manning, shares the developing story from the control room as tensions and excitement for a mission eight years in the making reached all new heights.

NASA's Mars Science Laboratory spacecraft, sealed inside its payload fairing atop the United Launch Alliance Atlas V rocket
NASA’s Mars Science Laboratory spacecraft, sealed inside its payload fairing atop the United Launch Alliance Atlas V rocket, launched on Nov. 26 from Kennedy Space Center in Florida.

5:45 a.m. PST (L-01:17:00)
I drove in this morning at 4:30 a.m. As usual, I was greeted by the cheery guards at the gate along with a small family of local deer, who keep sentry over a small patch of greenery at NASA’s Jet Propulsion Laboratory.

I quickly march into JPL’s mission control area to find the first shift quietly following the prelaunch procedure in sync with the Assembly, Test and Launch Operations (ATLO) procedure. They had been on station since 1:30 a.m. I tried that procedure at last week’s launch rehearsal and found the hour a bit unpleasant. Today, I am working on the Anomaly Response Team (ART) for post-launch anomalies. This means that if all goes well, I will have little to do but cheer when NASA’s Mars Science Laboratory rover launches. I have my own console where I can monitor both the spacecraft and listen to the voice nets (there are 10 of them!).

There are about 30 people here. Usually there are not as many, but today we have two people for every subsystem: power, thermal, propulsion, systems, fault protection, attitude control and management. I can hear the JPL ATLO test conductor, Art Thompson, at NASA’s Kennedy Space Center in Florida double check that the right sequence files have been sent. One in particular has commands that tell the rover when to automatically transition into “eclipse” mode. This software mode puts the entire vehicle into the configuration needed for the period prior to separation from the Centaur. In particular this mode turns on the descent stage and cruise stage tank heaters. This timer should be set about 15 minutes after launch, which is planned for 7:02 am PST today. It is an absolute time so they have to send a new time every time we have a new launch attempt. The voice net that is the most interesting is the launch vehicle’s fueling operations. I have not heard that one before. They are more than 50 percent of the way through fueling!

It is fun to see the crowd here. No dress code, but some have come in ties, others with pink mohawks. Nice combo. Professionals all. The peanuts have already made the rounds.

6:15 a.m. (L-00:47:00)
Brian Portock, today’s flight director at JPL, just finished the launch poll of the room to see if everyone is go for transition to launch mode. This is a command to the rover that will put everything on the rover into a mode that is used for the first 15 minutes of flight. In particular, the heaters are all put into a launch and cruise configuration. We expect that the cruise stage heaters will be on more than off due to the air conditioning needed to keep the spacecraft cool (hot generators, you know).

6:29 a.m. (L-00:33:00)
Arm pyros! Once these relays are closed, they will be that way for the next 8.5 months.

6:32 a.m. (L-00:30:00)
The data rate is lowered to launch nominal to 200 bits per second. This will allow the rover’s data to flow to both the ground (via wires to the power van at the foot of the launch pad that provides power to the rover before launch) and to the launch vehicle where it will be available throughout launch (very cool). The JPL management showed up. Charles Elachi is behind me. My old friend and JPL Chief Engineer Brian Muirhead is here with his family.

6:40 a.m. (L-00:22:00)
The flight director is doing the launch poll for the team here at JPL: “All stations at JPL report go.” ATLO is going through its poll at lightening speed. All stations go. This is going fast! The weather guys report of scattered skies at 5,000 feet looks good. I am getting excited.

6:47 a.m. (L-00:15:00)
We lost the flow of data from MSL via the Atlas Space Flight Operations Center (ASOC) land lines, but they switch it to the radio path from the launch vehicle, and it starts flowing again.

7:00 a.m. (L-00:02:00)
All Quiet. Peanuts going around the room again … everyone is excited!

7:01 a.m. (L-00:01:20)
Everything is armed …

7:01 a.m. (L-00:00:30)
GO ATLAS! GO CENTAUR!

7:03 a.m. (L+00:01:00)
GO, GO, GO!

7:06 a.m. (L+00:04:00)
Fairing falls off! Wind on MSL ;)

7:07 a.m. (L+00:05:00)
Rob Zimmerman, our power systems engineer, reports power on solar arrays! 3.3 x 2 = 6. 7 amps! The spacecraft is still power-negative for a while which means that the battery is still discharging. We need more sunlight - very soon.

7:11 a.m. (L+00:09:00)
Getting intermittent data from the rover via the Centaur. So far, no computer reboots!

7:12 a.m. (L+00:10:00)
The ATLO test conductor reports that they are done building and launching MSL (hey, it took ‘em long enough! ;) ). We all cheer and smile. They are supporting the cruise team now.

7:14 a.m. (L+00:12:00)
We’ve reached the end of the first burn (MECO1). All is well. Eighteen minutes to second burn. Battery is charging at 4.3 amps for each battery — very good.

7:17 a.m. (L+00:15:00)
The eclipse-mode transition should be done; don’t know yet. Got it. The tank heaters should be on now; They are. Batteries are still charging at 95 percent state of charge (SOC).

7:35 a.m. (L+00:33:00)
Waiting for telemetry from over Africa …

7:36 a.m. (L+00:34:00)
It’s five minutes to MECO2, pushing out of Earth orbit. Heavy rover! KEEP PUSHING! Mars awaits.

7:39 a.m. (L+00:37:00)
The spacecraft is nearly out of Earth orbit, six minutes until separation from Centaur upper stage. Everyone is relaxed, but there’s not a lot of data from the rover. It still says it is in launch mode — missed the data that said eclipse.

7:42 a.m. (L+00:40:00)
MECO2. next is turn to separation attitude and spin up. Separation! We get a beautiful view of MSL spinning away from us — in the right attitude and the right direction! (› See Video)

The
Video: The Mars Science Laboratory spacecraft separates from the upper stage of its Atlas V launch vehicle and heads on its way to Mars.
› See video

7:53 a.m. (L+00:51:00)
We have lock from NASA’s Deed Space Network in Canberra, Australia!

8:07 a.m. (L+01:05:00)
Data-slowing coming … All looks good, batteries at 98 percent. The rover is now in cruise mode. The heaters are on and cycling as designed. The spacecraft is spinning at 2.5 rotations per minute with only 1 degree of nutation (or swaying) — that is not a lot. The Atlas and Centaur did a fantastic job! The generator is working.

8:26 a.m. (L+01:24:00)
Now let’s try the uplink (sweep). Sweep is working! We have strong signals both ways. We are getting two-way Doppler - navigation says that the frequency is just a few hertz off so we had a very nominal injection to solar orbit. We can command!

Everyone is relaxed and trying to see if there is anything that looks wrong, but so far, nothing. Everything is fine. This is weird. Our bird is on its way - it’s where it belongs. We are happy to be in a completely new mode. No more last-minute fixes (to anything but the software). We have a lot to do, but at least our bird is on its way.


Comments on The Remarkable Spirit Rover

Wednesday, July 20th, 2011

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
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.”


A Heartfelt Goodbye to a Spirited Mars Rover

Wednesday, May 25th, 2011

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
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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Out of This World? The Mars Climate Change Mystery

Tuesday, February 15th, 2011

By Erik Conway, writing for My Big Fat Planet

Mars

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.


Over the Hills and through the Sand: Six Years of Driving on Mars

Thursday, December 31st, 2009
John Wright
John Wright

I almost didn’t get to drive the rovers.

As one of the five developers of the software used to build the command sequences and rehearse and visualize the rover activities, I really wanted to be one of the people using it in flight. Unfortunately, only three members of the team were selected to be Rover Planners (a job title we believe was chosen in place of Rover Drivers to make the job sound very boring and reduce competition for it). I was not one of them.

I was originally slated to be a downlink analyst looking at the telemetry from the rover to assess the driving and arm operations. This entailed months of training to learn how to run somebody else’s software, a much more difficult task than using your own. Fortunately for me, and unfortunately for someone else, a position opened up on the Rover Planner team and I was transferred over. This entailed more months of training to learn the procedures, but the fuse was very short since Spirit was careening towards its landing. The fact that I knew the software tools already was the saving grace that allowed me to be ready to go on landing day.

Looking back on these six years, I’m tired, but amazed, when I think about how much we’ve accomplished and continue to accomplish. During the prime mission, I remember hearing Steve Squyres say how much we would like Spirit to go explore the hills in the distance but that we would never get there. Well, we have driven to the top of those hills and down the other side.

I remember when Opportunity drove into Purgatory and the Rover Planners immediately said that we needed to back out of the sand dune. After months of testbed activities and review, the decision was made to back out of the sand dune. I can remember looking over at Scott Maxwell, another Rover Planner, and saying to each other “This is so cool!!” (We still say that).

Some of my favorite memories are of giving talks to school kids about what I do, though one of my saddest was being asked by one of the kids, an honor student, if the moon landings were faked. I especially enjoyed calling up Car Talk and asking the guys how to keep our electric vehicle running through the winter on Mars. I laugh when I think about a recent talk I had with Scott when the right front wheel of Spirit seemed to work again after four years of being dragged around. Scott said he didn’t know if we were driving with six wheels or only five. Immediately I jumped in, Dirty Harry-style, with, “I know what you’re thinking punk. Are we driving with six wheels or only five? To tell the truth, I don’t know myself. The question you have to ask yourself is, ‘Do I feel lucky?’ Well, do ya’, punk?”

As we work on getting Spirit out of the current sand trap, I feel manic-depressive about our chances. One day I am sure we will have no problem but the next day I am equally convinced that all is lost. This is about the toughest situation we have ever had to get out of. When we are stuck, it seems as if we are always running out of daylight, which translates to power. It happened at Tyrone, it happened at Tartarus, and it has happened at Troy.

Hmmm, maybe we should stop giving names to locations that start with T.


Got Water?

Tuesday, May 19th, 2009
Sue Smrekar
by Sue Smrekar
Deputy Project Scientist - Mars Reconnaissance Orbiter

A theme of Mars exploration is “Follow the Water,” since understanding the history of water on our planetary neighbor will help us understand if there were environments favorable for life to occur and how climate has changed over time. This is because all life on Earth requires water and we assume the same applies elsewhere in the universe. The Mars Reconnaissance Orbiter has made numerous discoveries that have provided new insights into past wet environments on Mars, water vapor in the planet’s current atmosphere and ice in the subsurface. However, so far, liquid water remains elusive.

The Shallow Radar, or “SHARAD” instrument is the only one on the Mars orbiter that was designed with a goal of discovering liquid water below Mars’ surface. This ground-penetrating radar instrument, which was supplied by the Italian Space Agency, transmits a radar signal at approximately 20 megahertz, and receives any radar waves that bounce off the surface or subsurface layers. The radar instrument has sufficient strength to see layers to a depth of about one kilometer (a little more than one-half mile), and even deeper in the polar caps. Layers in the subsurface reflect the radar wave if there is sufficient contrast in their dielectric properties (their bulk electrical properties), as for example between dry sand and ice-filled sand. Water is a much better conductor than other geologic materials, and thus should be readily detected if present.

Image taken from NASA's Mars Reconnaissance Orbiter
This image from NASA’s Mars Reconnaissance Orbiter shows gully channels in a crater in the southern highlands of Mars.The gullies emanating from the rocky cliffs near the crater’s rim (upper left) show meandering and braided patterns typical of water-carved channels. Image credit: NASA/JPL/University of Arizona

Of all the features believed to be formed by water on Mars, we have found only two gullies known to have recent flows – within the last 5-10 years. Gullies are narrow channels that emanate from cliff walls, starting well below the local ground surface. Dr. Michael Malin used the Mars Orbital Camera on Mars Global Surveyor to repeatedly image these features because of their fresh, unweathered appearance. These efforts led to the discovery of the two relatively new gullies.

To date, the Shallow Radar instrument’s observations of dozens of regions containing gullies show no evidence of liquid water. Since slopes of the cliffs where the two new gullies occur are extremely steep, some scientists put forth an alternate hypothesis in which dry debris tumbling downhill could have formed the latest channels. Yet many of the features observed at these and other gullies strongly suggest that liquid water had at least some role in carving the channels. These channels may have formed when a past climate change caused subsurface ice to melt. Or perhaps liquid water was trapped in a past aquifer. But for now, liquid water, if it exists today on Mars, remains out of reach of the Mars Reconnaissance Orbiter.


Growing Up With the Mars Rovers

Tuesday, January 20th, 2009
Ashley Stroupe
by Ashley Stroupe
Robotics Engineer

I am not supposed to be here, working with the Mars Exploration Rovers. There wasn’t supposed to be a Mars Rover here for me to work on. I arrived at JPL less than a month before Spirit’s landing in January 2004. Long before I earned the privilege of working on such a project, the three-month mission (six if we were lucky) would be completed. Robots are intricate machines, and Mars is a harsh place. Neither Spirit nor Opportunity should be here - and, as a result, neither should I be here to talk about them. Five years on Mars - inconceivable! But somehow, Spirit, Opportunity and I are celebrating our fifth anniversaries within a few weeks of each other. We’ve grown up together, in a way.

I have been working with the rovers for almost four and a half of their five years. I’ve discovered that Spirit and Opportunity are more than just a couple of robots or tools - they are a grand vision, a shared dream. A dream so powerful and so compelling that even those who come late to it, as I did, are fully invested. I look around at the room as I write this and I see people who have been here from the beginning (or even before the beginning from Pathfinder days in 1997) and I see the newest generations - those I have helped to train and with whom I have shared the vision. This dream is large enough for all of us.

spirit
This is a partial view of a spectacular image from Spirit atop “Husband Hill.” The rover tracks were my “first” on Mars.
Full image

Most engineers build a product and give it to the user. But those of us working on the Mars program are lucky enough to continue working with the scientists and get a real sense of the great purpose of what we do. We are an integral part of contributing to our understanding of the universe around us. I often step back and realize how truly fortunate I am, working on this amazing project with these remarkable, talented people.

This team of people is a family, and the rovers are our children. And, like parents of adult children who have moved away, we worry, we try to keep them safe, we try to teach them what we know and we give them guidance. Sometimes they listen and sometimes they don’t. But together, we’ve made amazing discoveries. Once Mars was a warmer place, a wetter place, a more Earthlike place - something we could only infer indirectly before. And it’s still a beautiful place with strangely colored sunsets that remind us we’re looking at another world.

Now, experience has matured us. And aged us. We have faced a lot of challenges. Racing to find places to survive harsh Martian winters, climbing mountains and crater walls, riding out dust storms, and working around arthritic body parts (broken wheels and failing arm joints). There have been sleepless nights and new gray hairs. But as Spirit and Opportunity begin long journeys to new places, we remember our starry-eyed youth and still nothing seems entirely out of reach. Five years on Mars? That’s just the beginning.


On the Road Again

Monday, October 6th, 2008
stroupe
by Ashley Stroupe
Robotics Engineer

The Mars Exploration Rovers, Spirit and Opportunity, have been exploring the geology of Mars for nearly five years - well beyond their expected lifetime of three to six months. In that time they have made amazing discoveries, most importantly finding proof that Mars was once a much wetter planet that may have been capable of supporting life. Spirit has been exploring a region around a small mountain range that seems to have once had hot water or steam, the very kind of place life might have originated on Earth. Opportunity has been investigating craters in the plains that provide views deep underground and show evidence of flowing water in the ancient past.

I am a roboticist at JPL, and just one member of the large team of people who work together to enable Spirit and Opportunity to explore. My work focuses on getting robots to do things intelligently, both by developing software for robot autonomy and by operating our two spacecraft on the surface of Mars.

Spirit and Opportunity have become like old friends to the operations team. Every day we are anxious to hear the latest news and see the snapshots taken from the new places they are visiting. Working with the rovers never gets routine as each new location brings new circumstances and new problems to solve.

spirit
The white-capped Von Braun hill in the distance is Spirit’s next destination.

The challenges of operating Spirit and Opportunity have continued to grow and change as they age, and we have had to develop new ways of driving and operating the robotic arm as capabilities decrease. We are discovering how to operate these rovers in ways for which they were never designed. The discovery process requires a lot of imagination and a lot of practice, both on Earth with our engineering rover and on Mars. It’s this kind of completely new and unanticipated problem that is the most fun for engineers like myself to solve.

Both rovers are now starting to show their old age of 4¾ years (that’s at least 300 in rover-years!), and some parts do not function quite as well as they used to. Spirit has to drive more slowly and constantly monitor her progress to make sure she is staying on the right path to compensate for a broken right front wheel that tends to dig into the soil. Opportunity has limited reach with her instrument arm due to a failed shoulder joint, and has to approach science targets in a very precise way. Despite these limitations, both rovers are now about to embark on difficult journeys which will require them to set new milestones and we will need to learn new ways of driving yet again.

After surviving a very difficult winter, Spirit is soon going to be heading south toward some interesting geological features: a hill called von Braun and a depression called Goddard. Scientists hope investigating these unique features will provide insights into the Martian past. They are looking for additional evidence of hot springs or steam vents that have been hinted at by other observations in this region. Based on comparisons to similar locations on Earth (like deep sea vents), this could be an ideal place for life. Reaching these exciting features requires a long drive through sandy terrain in a very short period of time before next winter arrives. This will mean pushing Spirit to new levels of performance.

endurance
Opportunity is getting ready to head for “Endeavour” crater, having finished up its study of “Victoria.”

Opportunity is finishing up her observations of the 800-meter Victoria crater and then will begin a 12-kilometer, two-year odyssey toward a huge crater (about 22 kilometers across) to the southeast. As this means more than doubling the total distance Opportunity has driven in her lifetime, we are excited to be developing new methods to make record distance drives safely. This will require relying on the rover’s onboard autonomy to keep her safe more than ever before as we drive each day well past what we can see.

Spirit and Opportunity’s story of continued exploration - boldly striking out after one new goal after another, far beyond their design lifetimes - is a genuinely inspiring one. It’s as if Magellan circumnavigated the Earth, then paused and said, ‘You know, that’s not good enough. Let’s go to the moon, too.’