After a lot of hard work spanning many years, a team of scientists have discovered something surprising. They’ve found abundant bacterial life in tiny cracks in undersea volcanic rock in the Earth’s crust. The bacteria are thriving in clay deposits inside these tiny cracks.
This discovery is generating new excitement around the hope of finding life on Mars.
The building blocks of life can, and did, spontaneously assemble under the right conditions. That’s called spontaneous generation, or abiogenesis. Of course, many of the details remain hidden to us, and we just don’t know exactly how it all happened. Or how frequently it could happen.
Scientist Carl Sagan said many times that “we are star stuff,” from the nitrogen in our DNA, the calcium in our teeth, and the iron in our blood.
It is well known that most of the essential elements of life are truly made in the stars. Called the “CHNOPS elements” – carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur – these are the building blocks of all life on Earth. Astronomers have now measured of all of the CHNOPS elements in 150,000 stars across the Milky Way, the first time such a large number of stars have been analyzed for these elements.
“For the first time, we can now study the distribution of elements across our Galaxy,” says Sten Hasselquist of New Mexico State University. “The elements we measure include the atoms that make up 97% of the mass of the human body.”
Astronomers with the Sloan Digital Sky Survey made their observations with the APOGEE (Apache Point Observatory Galactic Evolution Experiment) spectrograph on the 2.5m Sloan Foundation Telescope at Apache Point Observatory in New Mexico. This instrument looks in the near-infrared to reveal signatures of different elements in the atmospheres of stars.
While the observations were used to create a new catalog that is helping astronomers gain a new understanding of the history and structure of our galaxy, the findings also “demonstrates a clear human connection to the skies,” said the team.
While humans are 65% oxygen by mass, oxygen makes up less than 1% of the mass of all of elements in space. Stars are mostly hydrogen, but small amounts of heavier elements such as oxygen can be detected in the spectra of stars. With these new results, APOGEE has found more of these heavier elements in the inner part of the galaxy. Stars in the inner galaxy are also older, so this means more of the elements of life were synthesized earlier in the inner parts of the galaxy than in the outer parts.
So what does that mean for those of us out on the outer edges of one of the Milky Way’s spiral arms, about 25,000 light-years from the center of the galaxy?
“I think it’s hard to say what the specific implications are for when life could arise,” said team member Jon Holtzman, also from New Mexico State, in an email to Universe Today. “We measure typical abundance of CHNOPS elements at different locations, but it’s not so easy to determine at any given location the time history of the CHNOPS abundances, because it’s hard to measure ages of stars. On top of that, we don’t know what the minimum amount of CHNOPS would need to be for life to arise, especially since we don’t really know how that happens in any detail!”
Holtzman added it is likely that, if there is a minimum required abundance, that minimum was probably reached earlier in the inner parts of the Galaxy than where we are.
The team also said that while it’s fun to speculate how the composition of the inner Milky Way Galaxy might impact how life might arise, the SDSS scientists are much better at understanding the formation of stars in our Galaxy.
“These data will be useful to make progress on understanding Galactic evolution,” said team member Jon Bird of Vanderbilt University, “as more and more detailed simulations of the formation of our galaxy are being made, requiring more complex data for comparison.”
“It’s a great human interest story that we are now able to map the abundance of all of the major elements found in the human body across hundreds of thousands of stars in our Milky Way,” said Jennifer Johnson of The Ohio State University. “This allows us to place constraints on when and where in our galaxy life had the required elements to evolve, a sort ‘temporal Galactic habitable zone’”.
The catalog is available at the SDSS website, so take a look for yourself at the chemical abundances in our portion of the galaxy.
Evidence of water and a warmer, wetter climate abound on Mars, but did life ever put its stamp on the Red Planet? Rocks may hold the secret. Knobby protuberances of rock discovered by the Spirit Rover in 2008 near the rock outcrop Home Plate in Gusev Crater caught the attention of scientists back on Earth. They look like cauliflower or coral, but were these strange Martian rocks sculpted by microbes, wind or some other process?
When analyzed by Spirit’s mini-TES (Mini-Thermal Emission Spectrometer), they proved to be made of nearly pure silica (SiO2), a mineral that forms in hot, volcanic environments. Rainwater and snow seep into cracks in the ground and come in contact with rocks heated by magma from below. Heated to hundreds of degrees, the water becomes buoyant and rises back toward the surface, dissolving silica and other minerals along the way before depositing them around a vent or fumarole. Here on Earth, silica precipitated from water leaves a pale border around many Yellowstone National Park’s hot springs.
Both at Yellowstone, the Taupo Volcanic Zonein New Zealand and in Iceland, heat-loving bacteria are intimately involved in creating curious bulbous and branching shapes in silica formations that strongly resemble the Martian cauliflower rocks. New research presented at the American Geophysical Union meeting last month by planetary geologist Steven Ruff and geology professor Jack Farmer, both of Arizona State University, explores the possibility that microbes might have been involved in fashioning the Martian rocks, too.
A sizzling visit to El Tatio’s geysers
The researchers ventured to the remote geyser fields of El Tatio in the Chilean Atacama Desert to study an environment that may have mimicked Gusev Crater billions of years ago when it bubbled with hydrothermal activity. One of the driest places on Earth, the Atacama’s average elevation is 13,000 feet (4 km), exposing it to considerably more UV light from the sun and extreme temperatures ranging from -13°F to 113°F (-10° to 45°C). Outside of parts of Antarctica, it’s about as close to Mars as you’ll find on Earth.
Ruff and Farmer studied silica deposits around hot springs and geysers in El Tatio and discovered forms they call “micro-digitate silica structures” similar in appearance and composition to those on Mars (Here’s a photo). The infrared spectra of the two were also a good match. They’re still analyzing the samples to determine if heat-loving microbes may have played a role in their formation, but hypothesize that the features are “micro-stromatolites” much like those found at Yellowstone and Taupo.
Stromatolites form when a sticky film of bacteria traps and cements mineral grains to create a thin layer. Other layers form atop that one until a laminar mound or column results. The most ancient stromatolites on Earth may be about 3.5 billion years old. If Ruff finds evidence of biology in the El Tatio formations in the punishing Atacama Desert environment, it puts us one step closer to considering the possibility that ancient bacteria may have been at work on Mars.
Silica forms may originate with biology or from non-biological processes like wind, water and other environmental factors. Short of going there and collecting samples, there’s no way to be certain if the cauliflower rocks are imprinted with the signature of past Martian life. But at least we know of a promising place to look during a future sample return mission to the Red Planet. Indeed, according to Ruff, the Columbia Hills inside Gusev Crater he short list of potential sites for the 2020 Mars rover.
Steve Ruff paper comparing El Tatio with an early hot springs environment in Gusev Crater
Doesn’t it feel like the Universe is perfectly tuned for life? Actually, it’s a horrible hostile place, delivering the bare minimum for human survival.
Consider that incomprehensible series of events that brought you to this moment. In a way that we still don’t understand, a complex mix of chemicals came together in just the right combination to kick off the evolution of life.
Generation after generation of bacteria, insects, fish, lizards, mammals and eventually humans somehow successfully found a buddy and passed along their genetic material to another generation. Clever humans invented computers, the internet, YouTube, and somehow you found your way to this exact video, to hear these words. Whoa.
It’s amazing to consider the Universe we live in, and how it’s perfectly tuned for life. If just a single variable was a little bit different, life as we know it probably wouldn’t exist. Gravity might be a repulsive force. Pokemons might catch you.
Doesn’t it feel like the Universe was created especially for us? I mean, didn’t I already tell you that we’re all the center of the Universe?
I’m sad to say, but this couldn’t be further from the truth. The reality is that the Universe is 100% completely inhospitable. Well, apart from a thin layer on the surface of our Earth, but that’s got to be a rounding error. A fraction of a fraction of a fraction of the teeniest percent of the volume of the Universe. The rest of the Universe is bunk.
If I was plucked out of our cozy environment and dropped into the near vacuum of pretty much anywhere else, the only resource would be a handful of hydrogen atoms. And what can you do with a few hydrogen atoms? Nothing. It might even give Bear Grylls a run for his money. He might have a little more trouble on a star’s surface, crisping up in a heartbeat.
Into a black hole? Surface of a neutron star? Near an exploding supernova? Please enjoy the crushing pressures and hellish temperatures of Venus, or the freezing irradiated surface of Mars.
Earth itself is mostly a deathtrap. Travel down a few kilometers and you’d bake and crush from the rising temperatures of the Earth’s interior. Travel up and the air gets thin, cold and killy. In fact, without our technology heating, cooling, or helping us breathe, we wouldn’t last more than a few days on most of the planet.
When you think about the landscape of time, we even live in a brief thumbnail of a moment when Earth is hospitable. Over the next few billion years, the Sun is going to heat up to the point that the surface of Earth will resemble the surface of Venus. And then the last hospitable hidey-hole in the entire Universe, that we know of, will wink out. The Universe is as inhospitable as it could possibly be. That is, without being completely inhospitable.
Especially when you consider the timeframes, and the long future when all the stars have died, where there’s nothing but black holes and frozen matter, and the Universe finally ditches that rounding error, and becomes 100% purely inhospitable.
Cosmologists use a term known as the anthropic principle to explain this very special moment we find ourselves in. There’s the greater anthropic principle that says the Universe wouldn’t be here without us to observe it, but that seems nutty and egotistical.
The lesser anthropic principle says that if the Universe turned out any differently, we wouldn’t be here to observe it.
Imagine you threw a dart out the window of an airplane and it landed in a tiny spot on the surface of the Earth. What were the chances that it would land there? Almost zero. What a lucky spot.
You can imagine all kinds of other even more inhospitable Universes, where the conditions were never good enough for life to evolve, and so intelligent civilizations could never even ask the question, “Is Our Universe Perfect for Life.”
So when you look out across a meadow in the springtime. The birds are chirping, and there’s new growth everywhere, don’t forget about the boiling rock magma beneath your feet, the frigid air and then vacuum above your head, and the whole Universe of burning, radiating, impacting objects trying their best to kill you.
Of all the extreme environments in the Universe, which ones do you find most fascinating? Tell us in the comments below.
In addition to being the birthplace of humanity and the cradle of human civilization, Earth is the only known planet in our Solar System that is capable of sustaining life. As a terrestrial planet, Earth is located within the Inner Solar System between between Venus and Mars (which are also terrestrial planets). This place Earth in a prime location with regards to our Sun’s Habitable Zone.
Earth has a number of nicknames, including the Blue Planet, Gaia, Terra, and “the world” – which reflects its centrality to the creation stories of every single human culture that has ever existed. But the most remarkable thing about our planet is its diversity. Not only are there an endless array of plants, animals, avians, insects and mammals, but they exist in every terrestrial environment. So how exactly did Earth come to be the fertile, life-giving place we all know and love?
Earth is the only planet in our Solar System where life is known to exists. Note the use of the word “known”, which is indicative of the fact that our knowledge of the Solar System is still in its infancy, and the search for life continues. However, from all observable indications, Earth is the only place in our Solar System where life can – and does – exist on the surface.
This is due to a number of factors, which include Earth’s position relative to the Sun. Being in the “Goldilocks Zone” (aka. habitable zone), and the existence of an atmosphere (and magnetosphere), Earth is able to maintain a stable average temperature on its surface that allows for the existence of warm, flowing water on its surface, and conditions favorable to life.
The average temperature on the surface of Earth depends on a number of factors. These include the time of day, the time of year, and where the temperatures measurements are being taken. Given that the Earth experiences a sidereal rotation of approximately 24 hours – which means one side is never always facing towards the Sun – temperatures rise in the day and drop in the evening, sometimes substantially.
And given that Earth has an inclined axis (approximately 23° towards the Sun’s equator), the Northern and Southern Hemispheres of Earth are either tilted towards or away from the Sun during the summer and winter seasons, respectively. And given that equatorial regions of the Earth are closer to the Sun, and certain parts of the world experience more sunlight and less cloud cover, temperatures range widely across the planet.
However, not every region on the planet experiences four seasons. At the equator, the temperature is on average higher and the region does not experience cold and hot seasons in the same way the Northern and Southern Hemispheres do. This is because the amount of sunlight the reaches the equator changes very little, although the temperatures do vary somewhat during the rainy season.
The average surface temperature on Earth is approximately 14°C; but as already noted, this varies. For instance, the hottest temperature ever recorded on Earth was 70.7°C (159°F), which was taken in the Lut Desert of Iran. These measurements were part of a global temperature survey conducted by scientists at NASA’s Earth Observatory during the summers of 2003 to 2009. For five of the seven years surveyed (2004, 2005, 2006, 2007, and 2009) the Lut Desert was the hottest spot on Earth.
However, it was not the hottest spot for every single year in the survey. In 2003, the satellites recorded a temperature of 69.3°C (156.7°F) – the second highest in the seven-year analysis – in the shrublands of Queensland, Australia. And in 2008, the Flaming Mountain got its due, with a yearly maximum temperature of 66.8°C (152.2°F) recorded in the nearby Turpan Basin in western China.
Meanwhile, the coldest temperature ever recorded on Earth was measured at the Soviet Vostok Station on the Antarctic Plateau. Using ground-based measurements, the temperature reached a historic low of -89.2°C (-129°F) on July 21st, 1983. Analysis of satellite data indicated a probable temperature of around -93.2 °C (-135.8 °F; 180.0 K), also in Antarctica, on August 10th, 2010. However, this reading was not confirmed by ground measurements, and thus the previous record remains.
All of these measurements were based on temperature readings that were performed in accordance with the World Meteorological Organization standard. By these regulations, air temperature is measured out of direct sunlight – because the materials in and around the thermometer can absorb radiation and affect the sensing of heat – and thermometers are to be situated 1.2 to 2 meters off the ground.
Comparison to Other Planets:
Despite variations in temperature according to time of day, season, and location, Earth’s temperatures are remarkably stable compared to other planets in the Solar System. For instance, on Mercury, temperatures range from molten hot to extremely cold, due to its proximity to the Sun, lack of an atmosphere, and its slow rotation. In short, temperatures can reach up to 465 °C on the side facing the Sun, and drop to -184°C on the side facing away from it.
Venus, thanks to its thick atmosphere of carbon dioxide and sulfur dioxide, is the hottest planet in our Solar System. At its hottest, it can reach temperatures of up to 460 °C on a regular basis. Meanwhile, Mars’ average surface temperature is -55 °C, but the Red Planet also experiences some variability, with temperatures ranging as high as 20 °C at the equator during midday, to as low as -153 °C at the poles.
On average though, it is much colder than Earth, being just on the outer edge of the habitable zone, and because of its thin atmosphere – which is not sufficient to retain heat. In addition, its surface temperature can vary by as much as 20 °C due to Mars’ eccentric orbit around the Sun (meaning that it is closer to the Sun at certain points in its orbit than at others).
Since Jupiter is a gas giant, and has no solid surface, an accurate assessment of it’s “surface temperature” is impossible. But measurements taken from the top of Jupiter’s clouds indicate a temperature of approximately -145°C. Similarly, Saturn is a rather cold gas giant planet, with an average temperature of -178 °Celsius. But because of Saturn’s tilt, the southern and northern hemispheres are heated differently, causing seasonal temperature variation.
Uranus is the coldest planet in our Solar System, with a lowest recorded temperature of -224°C, while temperatures in Neptune’s upper atmosphere reach as low as -218°C. In short, the Solar System runs the gambit from extreme cold to extreme hot, with plenty of variance and only a few places that are temperate enough to sustain life. And of all of those, it is only planet Earth that seems to strike the careful balance required to sustain it perpetually.
Variations Throughout History:
Estimates on the average surface temperature of Earth are somewhat limited due to the fact that temperatures have only been recorded for the past two hundred years. Thus, throughout history the recorded highs and lows have varied considerably. An extreme example of this would during the early history of the Solar System, some 3.75 billion years ago.
At this time, the Sun roughly 25% fainter than it is today, and Earth’s atmosphere was still in the process of formation. Nevertheless, according to some research, it is believed that the Earth’s primordial atmosphere – due to its concentrations of methane and carbon dioxide – could have sustained surface temperatures above freezing.
Earth has also undergone periodic climate shifts in the past 2.4 billion years, including five major ice ages – known as the Huronian, Cryogenian, Andean-Saharan, Karoo, and Pliocene-Quaternary, respectively. These consisted of glacial periods where the accumulation of snow and ice increased the surface albedo, more of the Sun’s energy was reflected into space, and the planet maintained a lower atmospheric and average surface temperature.
These periods were separated by “inter-glacial periods”, where increases in greenhouse gases – such as those released by volcanic activity – increased the global temperature and produced a thaw. This process, which is also known as “global warming”, has become a source of controversy during the modern age, where human agency has become a dominant factor in climate change. Hence why some geologists use the term “Anthropocene” to refer to this period.
When talking about the temperatures of planets, there is a major difference between what is measured at the surface and what conditions exist within the planet’s interior. Essentially, the temperature gets cooler the farther one ventures from the core, which is due to the planet’s internal pressure steadily decreasing the father out one goes. And while scientists have never sent a probe to our planet’s core to obtain accurate measurements, various estimates have been made.
For instance, it is believed that the temperature of the Earth’s inner core is as high as 7000 °C, whereas the outer core is thought to be between 4000 and 6000 °C. Meanwhile, the mantle, the region that lies just below the Earth’s outer crust, is estimated to be around 870 °C. And of course, the temperature continues to steadily cool as you rise in the atmosphere.
In the end, temperatures vary considerably on every planet in our Solar System, due to a multitude of factors. But from what we can tell, Earth is alone in that it experiences temperature variations small enough to achieve a degree of stability. Basically, it is the only place we know of that it is both warm enough and cool enough to support life. Everywhere else is just too extreme!
At one time or another, all science enthusiasts have heard the late Carl Sagan’s infamous words: “We are made of star stuff.” But what does that mean exactly? How could colossal balls of plasma, greedily burning away their nuclear fuel in faraway time and space, play any part in spawning the vast complexity of our Earthly world? How is it that “the nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies” could have been forged so offhandedly deep in the hearts of these massive stellar giants?
Unsurprisingly, the story is both elegant and profoundly awe-inspiring.
All stars come from humble beginnings: namely, a gigantic, rotating clump of gas and dust. Gravity drives the cloud to condense as it spins, swirling into an ever more tightly packed sphere of material. Eventually, the star-to-be becomes so dense and hot that molecules of hydrogen in its core collide and fuse into new molecules of helium. These nuclear reactions release powerful bursts of energy in the form of light. The gas shines brightly; a star is born.
The ultimate fate of our fledgling star depends on its mass. Smaller, lightweight stars burn though the hydrogen in their core more slowly than heavier stars, shining somewhat more dimly but living far longer lives. Over time, however, falling hydrogen levels at the center of the star cause fewer hydrogen fusion reactions; fewer hydrogen fusion reactions mean less energy, and therefore less outward pressure.
At a certain point, the star can no longer maintain the tension its core had been sustaining against the mass of its outer layers. Gravity tips the scale, and the outer layers begin to tumble inward on the core. But their collapse heats things up, increasing the core pressure and reversing the process once again. A new hydrogen burning shell is created just outside the core, reestablishing a buffer against the gravity of the star’s surface layers.
While the core continues conducting lower-energy helium fusion reactions, the force of the new hydrogen burning shell pushes on the star’s exterior, causing the outer layers to swell more and more. The star expands and cools into a red giant. Its outer layers will ultimately escape the pull of gravity altogether, floating off into space and leaving behind a small, dead core – a white dwarf.
Heavier stars also occasionally falter in the fight between pressure and gravity, creating new shells of atoms to fuse in the process; however, unlike smaller stars, their excess mass allows them to keep forming these layers. The result is a series of concentric spheres, each shell containing heavier elements than the one surrounding it. Hydrogen in the core gives rise to helium. Helium atoms fuse together to form carbon. Carbon combines with helium to create oxygen, which fuses into neon, then magnesium, then silicon… all the way across the periodic table to iron, where the chain ends. Such massive stars act like a furnace, driving these reactions by way of sheer available energy.
But this energy is a finite resource. Once the star’s core becomes a solid ball of iron, it can no longer fuse elements to create energy. As was the case for smaller stars, fewer energetic reactions in the core of heavyweight stars mean less outward pressure against the force of gravity. The outer layers of the star will then begin to collapse, hastening the pace of heavy element fusion and further reducing the amount of energy available to hold up those outer layers. Density increases exponentially in the shrinking core, jamming together protons and electrons so tightly that it becomes an entirely new entity: a neutron star.
At this point, the core cannot get any denser. The star’s massive outer shells – still tumbling inward and still chock-full of volatile elements – no longer have anywhere to go. They slam into the core like a speeding oil rig crashing into a brick wall, and erupt into a monstrous explosion: a supernova. The extraordinary energies generated during this blast finally allow the fusion of elements even heavier than iron, from cobalt all the way to uranium.
The energetic shock wave produced by the supernova moves out into the cosmos, disbursing heavy elements in its wake. These atoms can later be incorporated into planetary systems like our own. Given the right conditions – for instance, an appropriately stable star and a position within its Habitable Zone – these elements provide the building blocks for complex life.
Today, our everyday lives are made possible by these very atoms, forged long ago in the life and death throes of massive stars. Our ability to do anything at all – wake up from a deep sleep, enjoy a delicious meal, drive a car, write a sentence, add and subtract, solve a problem, call a friend, laugh, cry, sing, dance, run, jump, and play – is governed mostly by the behavior of tiny chains of hydrogen combined with heavier elements like carbon, nitrogen, oxygen, and phosphorus.
Other heavy elements are present in smaller quantities in the body, but are nonetheless just as vital to proper functioning. For instance, calcium, fluorine, magnesium, and silicon work alongside phosphorus to strengthen and grow our bones and teeth; ionized sodium, potassium, and chlorine play a vital role in maintaining the body’s fluid balance and electrical activity; and iron comprises the key portion of hemoglobin, the protein that equips our red blood cells with the ability to deliver the oxygen we inhale to the rest of our body.
So, the next time you are having a bad day, try this: close your eyes, take a deep breath, and contemplate the chain of events that connects your body and mind to a place billions of lightyears away, deep in the distant reaches of space and time. Recall that massive stars, many times larger than our sun, spent millions of years turning energy into matter, creating the atoms that make up every part of you, the Earth, and everyone you have ever known and loved.
We human beings are so small; and yet, the delicate dance of molecules made from this star stuff gives rise to a biology that enables us to ponder our wider Universe and how we came to exist at all. Carl Sagan himself explained it best: “Some part of our being knows this is where we came from. We long to return; and we can, because the cosmos is also within us. We’re made of star stuff. We are a way for the cosmos to know itself.”
On Tuesday, December 16, 2014, NASA scientists attending the American Geophysical Union Fall Meeting in San Francisco announced the detection of organic compounds on Mars. The announcement represents the discovery of the missing “ingredient” that is necessary for the existence – past or present – of life on Mars.
Indeed, the extraordinary claim required extraordinary evidence – the famous assertion of Dr. Carl Sagan. The scientists, members of the Mars Science Lab – Curiosity Rover – mission, worked over a period of 20 months to sample and analyze Martian atmospheric and surface samples to arrive at their conclusions. The announcement stems from two separate detections of organics: 1) ten-fold spikes in atmospheric Methane levels, and 2) drill samples from a rock called Cumberland which included complex organic compounds.
Methane, of the simplest organic compounds, was detected using the Sample Analysis at Mars instrument (SAM). This is one of two compact laboratory instruments embedded inside the compact car-sized rover, Curiosity. Very soon after landing on Mars, the scientists began to use SAM to periodically measure the chemical content of the Martian atmosphere. Over many samples, the level of Methane was very low, ~0.9 parts per billion. However, that suddenly changed and, as scientists stated in the press conference, it was a “wow” moment that took them aback. Brief daily spikes in Methane levels averaging 7 parts per billion were detected.
The detection of methane at Mars has been claimed for decades, but more recently, in 2003 and 2004, independent research teams using sensitive spectrometers on Earth detected methane in the atmosphere of Mars. One group led by Vladimir Krasnopolsky of Catholic University, and another led by Dr. Michael Mumma from NASA Goddard Space Flight Center, detected broad regional and temporal levels of Methane as high as 30 parts per billion. Those announcements met with considerable skepticism from the scientific community. And the first atmospheric measurements by Curiosity were negative. However, neither group backed down from their claims.
The sudden detection of ten-fold spikes in methane levels in Gale crater is not inconsistent with the earlier remote measurements from Earth. The high seasonal concentrations were in regions that do not include Gale Crater, and it remains possible that the Curiosity measurements are of a similar nature but due to some less active process than exists at the regions identified by Dr. Mumma’s team.
The NASA scientists at AGU led by MSL project scientist Dr. John Grotzinger emphasized that they do not yet know how the methane is being generated. The process could be biological or not. There are abiotic chemical processes that could produce methane. However, the MSL SAM detections were daily spikes and represent an active real on-going process on the red planet. This alone is a very exciting aspect of the detection.
The team presented slides to describe how methane could be generated. With the known low background levels of methane at ~ 1 part per billion, an external cosmic source, for example micro-meteoroids entering the atmosphere and releasing organics which is then reduced by sunlight to methane, could be ruled out. The methane source must be of local origin.
The scientists illustrated two means of production. In both instances, there is some daily – or at least periodic – activity that is releasing methane from the subsurface of Mars. The source could be biological which is accumulated in subsurface rocks then suddenly released. Or an abiotic chemistry, such as a reaction between the mineral olivine and water, could be the generator.
The subsurface storage mechanism of methane proposed and illustrated is called clathrate storage. Clathrate storage involves lattice compounds that can trap molecules such as methane which can subsequently be released by physical changes in the clathrate, such as solar heating or mechanical stresses. Through press Q&A, the NASA scientists stated that such clathrates could be preserved for millions and billions of years underground.
The second discovery of organics involved more complex compounds in surface materials. Also since arriving at Mars, Curiosity has utilized a drilling tool to probe the interiors of rocks. Grotzinger emphasized how material immediately at the surface of Mars has experienced the effects of radiation and the ubiquitous soil compound perchlorate reducing and destroying organics both now and over millions of years. The detection of no organics in loose and exposed surface material had not diminished NASA scientists’ hopes of detecting organics in the rocks of Mars.
Drilling was performed on several selected rocks and it was finally a mud rock called Cumberland that revealed the presence of organic compounds more complex than simple methane. The scientists did emphasize that what exactly these organic compounds are remains a mystery because of the confounding presence of the active chemical perchlorate which can quickly breakdown organics to simpler forms.
The detection of organics in the mud rock Cumberland required the drilling tool and also the scoop on the multifaceted robotic arm to deliver the sample into the SAM laboratory for analysis. To detect methane, SAM has an intake valve to receive atmospheric samples.
Dr. Grotzinger described how Cumberland was chosen as a sample source. The rock is called a mud stone which has undergone a process called digenesis – the metamorphosis of sediment to rock. Grotzinger emphasized that fluids will move through such rock during digenesis and perchlorate can destroy organics in the process. Such might be the case for many metamorphic rocks on the Martian surface. The panel of scientists showed a comparison between rock samples measured by SAM. Two in particular – from the rock “John Klein” and the Cumberland rock — were compared. The former showed no organics as well as other rocks that were sampled; but Cumberland’s drill sample from its interior did reveal organics.
The analysis of the work was painstaking – harking back to the Sagan statement. The importance of discovering organics on Mars could not be understated by the panel of scientists and Grotzinger called these two discoveries as the lasting legacy of the Mars Curiosity Rover. Furthermore, he stated that the discovery and analysis methods will go far to guide the choice of instruments and their use during the Mars 2020 rover mission.
The discovery of organics completes the necessary set of “ingredients” for past or present life on Mars: 1) an energy source, 2) water, and 3) organics. These are the basic requirements for the existence of life as we know it. The search for life on Mars is still just beginning and the new discoveries of organics is still not a clear sign that life existed or is present today. Nevertheless, Dr. Jim Green, introducing the panel of scientists, and Dr. Grotzinger both emphasized the magnitude of these discoveries and how they are tied into the objectives of the NASA Mars program — particularly now with the emphasis on sending humans to Mars. For the Mars Curiosity rover, the journey up the slopes of Mount Sharp continues and now with greater earnestness and a continued search for rocks similar to Cumberland.