Posts Tagged ‘Red Planet’

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.


Slice of History: Viking Stereo Viewer

Tuesday, December 4th, 2012

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 ViewerViking 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.


Landing Curiosity - NASA’s Next Mars Rover

Sunday, August 5th, 2012

By Doug Ellison

Follow the excitement as NASA prepares to land, Curiosity, its most technically advanced rover ever on Mars. JPL Visualization Producer Doug Ellison shares live, behind-the-scenes action from the mission control room at NASA’s Jet Propulsion Laboratory in Pasadena, Calif..

Artist's concept of NASA's Mars rover Curiosity

TOUCHDOWN

Monday, August 6, 2012 1:13:26 AM

Welcome to Gale Crater. “Adam…you’re a genius!” I shout to Adam Steltzner. He pauses. Stops. Turns around. “I’m not a genius — I just work with a team of them.”

Thanks for the ride

Sunday, August 5, 2012 10:04:10 PM

The EDL Phase Lead, Adam Steltzner, has just thanked the cruise team for their 350-million-mile ride. “Curiosity is in fantastic shape, she’s here because you guys got her here. See you on Mars.”

Go Curiosity. And break out the peanuts.

Mars really has us now.

Sunday, August 5, 2012 10:03:56 PM

Ten thousand and sixty three. Sixty four. Sixty five. As quick as you can count it, our speed towards Mars is accelerating.

Mars is about half the diameter of Earth, but only about 10 percent as heavy as Earth. Even so — on its surface, gravity is about 38 percent that of Earth. In the next 28 minutes, we will gain another 3,000 miles per hour until Curiosity, heatshield ready, slams into the top of the Martian atmosphere.

40 billion to 1

Sunday, August 5, 2012 9:15:28 PM

A quiet approach to Mars as we watch a tiny plot of a graph. The X-band frequency that Curiosity is currently transmitting is a frequency of more than 8 Gigahertz — 8 billion cycles per second. As it rotates, that tiny little graph shows that frequency moving up and down, by about 0.2 Hz. One part in 40 billion. That little bounce up and down is the rotation of the spacecraft, two revolutions per minute. We have that accuracy because we’re bouncing a radio signal from the ground, up to spacecraft and back again. But that signal, after a final poll, will be going away.

Systems Go. Power Go. Thermal Go. Propulsion Go. Nav Go. Uplink Go. Avionics Go. Flight. Software Go. Fault Protection Go. Chief Engineer Go. EDL FLight System Go. Data Management Go. GDS Go. Telecom Go. ACS Go. EDL Activity Lead Go. ACE Go.

“You are clear to bring down the uplink.” So in just over 13 minutes time, Curiosity will no longer have that amazing signal to bounce back - and our little squiggly 1-in-40-billion line will be gone. We will just hear the spacecraft’s own transmitter from more than 150 million miles.

Curiosity is truly on her own.

A Final Check

Sunday, August 5, 2012 8:44:21 PM

This full poll of the flight team is a lengthy and exhaustive tour of the rover, the cruise stage and all the systems. My favorite call is from the chief engineer:

“We are green across the board”

That’s the word from Rob Manning — a veteran of four successful Mars landings. When Rob says things are green, you know you’re in good shape. If you were hoping to spend some time exploring the martian moon Deimos on your way to Gale Crater — please alight the rover now, we just crossed its orbit. Now there are 16,000 miles to go.

Calm before the Storm

Sunday, August 5, 2012 8:32:58 PM

Things got a little quiet in the control room. People heading out for some food before we get down to the business of landing on Mars. It takes huge team to watch over a spacecraft as complex, and activites and intricate as a Mars landing. As they get back to their consoles, they do a comm check to make sure they can all hear each other. Systems. Power. Thermal. Prop. Nav. Uplink. Flight Software. Fault Protection. EO Team Chief. GDS. Telecom. EDL Comm. ACS … the calls, and acronyms, go on and on. Now they are all back on console, the whole team is about to do a full system poll.

Can you hear me?

Sunday, August 5, 2012 7:59:37 PM

Between now and landing, Curiosity will use a total of eight antennas. The Deep Space Network is now listening to a medium-gain antenna transmitting on X-Band on the cruise stage. During entry, two low gain antennas on the back of the spacecraft continue that signal of “tones.” There are also low-gain antennas on the descent stage and the rover. However, Earth will have set at this time.

Meanwhile, a UHF antenna on the backshell, followed by another on the descent stage and finally one on the rover, will continue to transmit telemetry during landing. This data will be received by Mars Odyssey and Mars Reconnaissance Orbiter. Odyssey will relay it straight to Earth so we can track landing. Mars Reconnaissance Orbiter records everything it hears and sends it back a few hours later. Mars Express will also record just the pitch of this signal as a final backup.

The ground stations at the Canberra, Australia Deep Space Communications Complex will follow us the whole way — direct from the rover ’til Earth sets behind it — and from Odyssey and Mars Reconnaissance Orbiter as well. All the way to the ground, a complex system of systems will be trying to keep that tenuous link between Earth and Mars alive.

Nominal!

Sunday, August 5, 2012 5:58:00 PM

“Nominal” sounds like a very boring word, but in the world of spaceflight, nominal is engineer for “awesome.” Thanks to the Deep Space Network, we know just how nominal everything is. Deep Space Station 43, a 70-meter-diameter antenna in Tidbindilla, Austraila is currently receiving a steady stream of data at 2,000 bits per second that informs the engineers how all their subsystems are doing. Attitude control, thermal performance, power systems, avionics, propulsion, communication, the list is long. The flight team (meet them all here: www.gigapan.com/gigapans/110926) just took a poll, and all subsystems are nominal. The MEDLI instrument is now powered up, and healthy. It’s talking to the flight computer, and the power system can see it drawing just 300 milliamps. It will record first-of-its-kind data on temperature, pressure and other readings through Curiosity’s heatshield during entry. This data will help us understand how the heatshield behaves and can help us make them better for the future. As MEDLI lives on the inside of the heatshield, it is thrown overboard when the heatshield is separated about six miles above the surface. Its data will be safely stored on the rover to be downlinked after landing.

Spin

Sunday, August 5, 2012 1:15:54 PM

When you’re a spacecraft it’s important to know which way you’re facing. If you know which way you’re facing, you know which way Earth is, so you can talk to home; which way the sun is, so you can get power on a solar array; and if you’re Curiosity, you know which way Mars is. There are two ways spacecraft typically orient themselves. One is called “three-axis stabilized,” which means the spacecraft uses thrusters and reaction wheels to keep itself pointed the right way. You may have heard about trouble with reaction wheels on the Mars Odyssey orbiter recently (it carries a spare just in case, and we’re now using it). Curiosity (as well as its older sisters Spirit and Opportunity, and Juno right now on its way to Jupiter) just spin their way through deep space. They point in one direction and spin, like a top. That spin stops the spacecraft wandering off and pointing somewhere else. Curiosity, all the way till after we wave goodbye to its cruise stage about 17 minutes before landing, spins at 2 rpm. During its 253-day cruise, Curiosity will have spun more than 720,000 times. It’s enough to give a rover a headache.

Three Degrees

Sunday, August 5, 2012 1:05:01 PM

I’ve arrived “on lab” (JPL-speak for “at the office”) to check up on our computer running Eyes on the Solar System (http://eyes.nasa.gov) that will be fed to NASA Television tonight. Looking up in the control room — I see we’ve just crossed 80,000 miles to go. Less than four- times the distance from Earth to our geostationary communication satellites. Mars is about 4,200 miles in diameter - so with a little high school trig, we can calculate that Mars would appear 3 degrees across to Curiosity. That’s six times larger than the size of the full moon from Earth. This time yesterday, Curiosity was only 170 mph slower than it is now. In the next 10 hours as it falls to Mars it gains another 5,000. As an astronaut onboard Apollo 13 said to mission control on their way home, “The world’s getting awful big in the window.”

The Runners Up

Friday, August 3, 2012 11:15:00 AM

Adam Steltzner (MSL EDL phase lead) is a great speaker and real highlight of today’s NASA Social event. A fantastic question from the audience asked what ideas for landing Curiosity were rejected.

The runner-up: airbags. There isn’t a fabric that we know of strong enough to handle the impact loads that a 899-kg rover would create. Good enough for the 180-kg of Spirit and Opportunity, but it just can’t get scaled up to something as big as Curiosity.

Third place: Put the rover on top of the rockets. The problem there is that the rover is so heavy, and the propellant tanks so large, that you would have a very tall vehicle prone to toppling over on touchdown.

It may look a little crazy — but the skycrane actually makes a lot of sense.

Speed Up, Slow Down

Thursday, August 2, 2012 5:12:47 PM

The art of flying between the planets is a balancing act of gravity, velocity, trajectory and timing. These variables come to a thrilling climax on Sunday evening as Curiosity reaches the Red Planet.

Launched into a trajectory around the sun in November 2011, Curiosity is currently in a solar orbit that just reaches the orbit of Mars. That trajectory means that, from the perspective of the sun, by noon Pacific time on August 1 Curiosity was travelling at 47,500 miles per hour. Yet Mars is travelling at more than 53,000 mph — some 5,500 mph faster than Curiosity. Left alone, Curiosity would soon begin a slow cruise back towards the orbit of Earth, while Mars would carry on along its own, faster trajectory.

But breathtaking accuracy by the navigation team guiding Curiosity means that Mars will be at the right place Sunday to pick up Curiosity. The planet’s gravity will speed up the spacecraft by 13,000 mph (as viewed from the sun) until their speeds match and Curiosity is safely on the surface. On the freeway of interplanetary navigation, Curiosity is the bug, and Mars is the windshield. To get ready for a martian year of exploration, you’ve got to take a big hit.

Welcome to the Landing Blog

Thursday, August 2, 2012 5:12:16 PM

Welcome to the Curiosity landing blog. I’m Doug Ellison, a visualization producer here at JPL. Our group is responsible for many of the graphics you will see that show how Curiosity has made its way to Mars, and what it will do when it gets there.

The landing animation was a nine-month-long project of obsessing over details of every piece of the spacecraft and its adventure. We’ve launched a special version of Eyes on the Solar System at http://eyes.nasa.gov that lets you ride with Curiosity all the way to the surface. We’ve become so familiar with the spacecraft and what it does that we even surprise the mission team themselves sometimes!

On landing night, I’ll be in our mission control (the “Dark Room”) keeping you up to date with some of the goings-on as Curiosity approaches Mars. Until then I’ll post a few little factoids about Curiosity, its trip to Mars, and its epic landing at Gale Crater.