Credit: NASA/JPL-Caltech/Cornell University/Arizona State University. Colorization by Stuart Atkinson.
Imagine if you were standing on Mars, beside the Opportunity rover, high on the summit of Cape Tribulation. You don’t have to leave too much to the imagination, thanks to imaging enthusiast Stu Atkinson. He’s put together a magnificent colorized version of Oppy’s recent panoramic view, atop the highest elevation that the rover will ever reach, perched on the west rim of Endeavour crater.
Click the image for the full view.
It’s quite the spectacular view for the rover that keeps going and going, with over 11 years of trekking across Mars. You can see haze and hills off in the distance, and a horizon that continues to beckon. According to Larry Crumpler from the MER science team, if you look closely at the image — from Oppy’s viewpoint — you can see all the way to the other side of the crater.
“We can see the rim looking north along the path to this location, and we can see far to the south, including another large impact crater that lies 10 km or so south of Endeavour,” Crumpler wrote in the rover field reports published on the New Mexico Museum of Natural History & Science’s website.
Here’s a map created by Crumpler of the Opportunity rover’s location at Cape Tribulation:
A map showing the location on the local summit of Cape Tribulation (1 m contours) and the geology up to this location. Credit: Larry Crumpler/MER Science Team/New Mexico Museum of Natural History & Science.
And here’s the black and white panorama from Arizona State Univerity:
Sol 3906, January 19, 2015. Summit panorama from Cape Tribulation from the Opportunity Mars Rover. Credit: NASA/Arizona State University.
Stu wrote poetically about the image on his website, explaining that the rover is looking down from the summit of Cape Tribulation, “with gorgeous views of the rim of Endeavour on the farside of the crater and of her tracks leading back down the hill to the great Merdiani Plain far below.”
Stu also explained his motivation for the work he does in enhancing the raw images sent from Mars:
What I try to create with my images is a vision of Mars, something that puts across – hopefully – the beauty of the planet and its landscapes. So my images are not photo-realistic, and I don’t claim them to be, but they, I hope, one person’s depiction of Mars which reflect the planet’s incredible raw beauty and nobility.
We only hope Stu, that like the rover, you keep going and going with your image processing wizardry too!
Are we seeing the convergence of a century of space science and science fiction before our eyes? Will Musk and SpaceX make 2001 Space Odyssey a reality? (Credit: NASA, Illustration, Judy Schmidt)
Truly a man for all seasons, Elon Musk’s next big thing is to build an internet for when people start arriving on Mars.
“It will be important for Mars to have a global communications network as well,” he told Bloomberg Businessweek. “I think this needs to be done, and I don’t see anyone else doing it.”
But his plan should also help bring higher speed internet to more places on Earth.
Musk’s idea is to place hundreds of satellites in orbit about 1,200 km (750 miles) above Earth, according to the article. Some satellites could be placed in lower orbit to help improve internet speeds and accessibility across Earth.
It would be an incremental process, and proceeds from the Earth internet could will help pay for the $10 billion investment in the colony and internet on Mars, Musk said.
“People should not expect this to be active sooner than five years,” he said. “But we see it as a long-term revenue source for SpaceX to be able to fund a city on Mars. … Our focus is on creating a global communications system that would be larger than anything that has been talked about to date.”
Because light travels much faster in the vacuum of space, internet connections will be improved over existing fiber optic cables. “The long-term potential is to be the primary means of long-distance Internet traffic and to serve people in sparsely populated areas,” said Musk, quoted by Businessweek.
The final chapter in the saga of a wayward Mars lander was finally revealed today, as an international team released images showing the Beagle-2 lander’s final resting place on Mars.
Flashback to Christmas Day, 2003. While most folks gathered ‘round the tree and opened presents, the UK and European Space Agency awaited a gift from space. The Beagle-2 Mars lander had been released from the European Space Agency’s Mars Express orbiter six days prior, and was coasting towards a perilous landing in Isidis Planitia and was set to phone home.
All was going according to plan, and then… silence.
It’s the worst part of any mission, waiting for a lander to call back and say that it’s safe and sound on the surface of another world. As the hours turned into days, anxious engineers used NASA’s Mars Odyssey spacecraft and the Lovell Telescope at Jodrell Bank to listen for the signal.
Beagle-2 was declared lost a few weeks later on February 6th, 2004.
But now, there’s a final twist to the tale to tell.
Beagle 2, partially deployed on the Martian surface. Credit and Copyright: HiRISE/NASA/Leicester.
The UK Space Agency, working with ESA and NASA announced today that debris from the landing site had been identified and that indicates — contrary to suspicions — that Beagle-2 did indeed make it to the surface of the Red Planet intact. New images from the Mars Reconnaissance Orbiter released today suggest that not only did Beagle-2 land, but that its airbags did indeed deploy properly and that the dish-shaped 1-meter in diameter spacecraft partially unfolded pocket-watch style after it had bounced to a stop.
“We are very happy to learn that Beagle 2 touched down on Mars,” said ESA’s Director of Science and Robotic Exploration in a recent press release. “The dedication of the various teams in studying high-resolution images in order to find the lander is inspiring.”
So, what went wrong with Beagle-2?
At this point, no further speculation as to what caused the lander to fall silent has been forthcoming, but today’s revelation is sure to rewrite the final saga of Beagle-2.
“Not knowing what happened to Beagle-2 remained a nagging worry,” said ESA’s Mars Express project manager Rudolf Schmidt. “Understanding now that Beagle-2 made it all the way down to the surface is excellent news.”
Speculation swirled across the internet earlier this week as the UK Space Agency and ESA suggested that new information as to the fate of Beagle-2 was forthcoming, over 11 years after the incident. Back in 2004, it was suggested that Beagle-2 had encountered higher levels of dust in the Martian atmosphere than expected, and that this in turn resulted in a failure of the spacecraft’s parachutes. Presumably, the lander then failed to slow down sufficiently and crashed on the surface of Mars, the latest victim of the Great Galactic Ghoul who seems to love dining on human-built spacecraft bound for the Red Planet.
An artist’s conception of Beagle-2 fully deployed on Mars. Credit: ESA.
The loss of Beagle-2 wasn’t only a blow to the UK and ESA, but to its principal investigator Colin Pillinger as well. Pillinger was involved in the search for Beagle-2 in later years, and also played a part in the Rosetta mission to Comet 67P/Churyumov-Gerasimenko as well. Unfortunately, Pillinger passed away in May of last year from a brain hemorrhage. A portion of the western rim of Endeavour Crater currently being explored by Opportunity was named Pillinger Point in his honor.
Today’s announcement has triggered a wave of congratulations that the 11-year mystery has been solved. There have even been calls on Twitter and social media to rename the Beagle-2 site Pillinger Station.
“The history of of space exploration is marked by both success and failure,” Said Dr. David Parker, the Chief Executive of the UK Space Agency in a recent press release. “This finding makes the case that Beagle-2 was more of a success than we previously knew and undoubtedly an important step in Europe’s continuing exploration of Mars.”
Evidence of the successful landing of Beagle-2. Click here for the animated .gif version. Credit: University of Leicester/Beagle 2/NASA/University of Arizona.
Beagle-2 is about 2 metres across unfurled, and came to rest within 5 kilometres of its target location.
There have been false announcements of the discovery of Beagle-2 before. Back in late 2005, a claim was made that the lander had been spotted by Mars Global Surveyor, though later searches came to naught.
“I can imagine the sense of closure that the Beagle-2 team must feel,” Said JPL’s MRO project scientist Richard Zurek in a recent press release. “MRO has helped find safe landing sites on Mars for the Curiosity and Phoenix missions and has searched for missing craft to learn what may have gone wrong. It’s an extremely difficult task.”
MRO entered orbit in March 2006 and carries a 0.5 metre in diameter HiRISE camera capable of resolving objects just 0.3 metres across on the surface of Mars. The European Space Agency’s Mars Express orbiter that carried Beagle 2 is also still in operation, along with NASA’s aging Mars Odyssey spacecraft. These were joined in orbit by MAVEN and India’s Mars Orbiter just last year.
Beagle-2 encapsulated in the lab. All rights reserved, Beagle-2.
Of course, getting to Mars is tough, and landing is even harder. Mars has just enough atmosphere that you have to deal with it, but it’s so tenuous – 0.6% the surface pressure of Earth’s atmosphere at sea level – That it doesn’t provide a whole lot of usable drag.
To date, only NASA had successfully landed on Mars, and done it seven times – only the Mars Polar Lander failed back in 1999. The Russians fared much worse, with their most successful lander being Mars 3, which sent back only one blurry image before falling silent.
ESA and the Russian Federal Space Agency hope to amend that with the launch of the ExoMars mission next year, slated to land on Mars in 2018.
I remember waiting with millions of other space fans for word back from Beagle 2 on Christmas Day 2003. Think back to what your internet connection was like over 11 years ago, in an era before smart phones, Twitter and Facebook. We’d just come off of the spectacular 2003 Mars opposition season, which provided the orbital geometry ideal for launching a mission to the Red Planet. This window only comes around once every 26 months.
Though Beagle 2 was a stationary lander akin to the Viking and Mars Phoenix missions, it had a robotic arm and a clever battery of experiments, including ones designed to search for life. The signal it was supposed to use to call home was designed by the UK pop rock band Blur, a jingle that never came.
Alas, we’ll have to wait to see what the alien plains around Isidis Planitia actually look like, just 13 degrees north of the Martian equator. But hey, a lingering mystery of the modern age of planetary exploration was solved this week.
Still, we’re now left with a new dilemma. Does this mean we’ll have to write a sequel to our science fiction short story The Hunt for Beagle?
The surface of Mars is a well worn place in the Solar System, heavily pounded by countless meteor impacts. And some of these craters are hundreds of millions of years old. So it’s unusual for there to be a completely fresh impact on the surface of Mars: but that’s just what NASA scientists discovered looking through a recent batch of images returned from NASA’s Mars Reconnaissance Orbiter.
You’re looking at an image taken by the Mars Context Camera, an instrument on board the Mars Reconnaissance Orbiter. In an older photograph taken of the region in February 2012, there was just a bunch of old craters. And then, in the newer image, taken June 2014, this fresh scar on the surface of Mars is clearly visible.
No crater… then crater. Credit: NASA/JPL/UA
The crater itself is circular, but the blast of ejecta indicates that the object came in from the West, and struck the surface of Mars, blasting out a curtain of pulverized rock that covered the nearby surface. The impactor would have vaporized into a fireball of superheated rock, like a nuclear bomb exploding on the surface of Mars, while the eject blanket was shot out to the side.
This isn’t the first time spacecraft have detected new craters on Mars. In fact, the largest new crater discovered was half the length of a football field. And so far, researchers have turned up more than 400 new craters on the surface of Mars.
The Mars Context Camera has completely imaged the entire surface of Mars at least once during its 7-year mission. And with multiple passes, planetary scientists are starting to build up a picture of how the dynamic the surface of Mars can really be.
Largest new crater ever discovered. Credit: NASA/JPL/UA
And of course, planetary scientists have discovered fresh craters on other locations in the Solar System. NASA’s Lunar Impact Monitoring Program turned up a bright meteoroid impact on March 17, 2013, and follow on observations by NASA’s Lunar Reconnaissance Orbiter turned up the impact location. The monitoring program has actually turned up more than 300 impacts so far. So if you’re walking around on the Moon, watch your head.
Bright impact flash made by a foot-wide rock that struck the moon on March 17, 2013. The moon was a crescent in the evening sky at the time. The impact occurred in the dark, earthlit part of the moon away from the sun-lit crescent. Credit: NASALeft: Fresh material brought to the surface makes the new 59-foot-wide crater look like it was spray painted white. Credit: NASA/GSFC/Arizona State University. Right: The meteoroid strike occurred near the familiar crater Copernicus in the Sea of Rains (Mare Imbrium). Credit: Bob King
Artist's conception of Mars One human settlement. Credit: Mars One/Brian Versteeg
While the world’s attention last year was focused on Mars One’s audacious plan to send people on a one-way trip to the Red Planet — not everyone thinks they’ll make it — the private organization has a much closer goal in its sights: landing a robotic mission there in 2018.
The goal is also audacious. Only NASA landers have worked for more than a few moments on the Red Planet, and even the agency it has experienced many failures along the way. Mars One is hoping to succeed using the design for the Phoenix northern mission, which is being duplicated somewhat in the upcoming 2016 Insight drill mission.
“We’re very lucky to have Lockheed Martin on the contract,” said founder Bas Lansdorp in a phone interview with Universe Today. He noted the company built the Phoenix lander, and that Mars One trusts Lockheed so much that the firm is being allowed to pick its own subcontractors for the mission.
Also on that mission will likely be the winner of a Mars One university competition to send an experiment to Mars. Called Seed, the proposal would see the first seed grown on Mars. The plant (called Arabidopsis thaliana, a common feature of space studies) would grow inside an external container that would protect it from the surrounding environment. The team is composed of students from the University of Porto, MIT Portugal and the University of Madrid.
The Mars Phoenix Lander thundered off of Cape Canaveral Air Force Station’s Space Launch Complex 17 in the summer of 2007. About nine months later – it landed on the surface of Mars. Image Credit: NASA/JPL
“The Seed experiment group, they have really put a lot of effort into creating public awareness of what they are doing, and they collected a lot of votes,” Lansdorp said. While the project also had to meet stringent technical requirements, it was the efforts at public support that were an “important reason” as to why they won, he added.
But even now, their flight is not a guarantee. Seed will need to fund the development and construction of its experiment. (Flight costs are taken care of by Mars One.) Also, the group will need to pass technical milestones between now and 2018. If for some reason Seed does not make it, Mars One would instead go to one of two backup projects. These would be selected from the second- and third-place winners, which are respectively, Cyano Knights and Lettuce on Mars.
As for Mars One’s funding, the organization eventually hopes to receive money from broadcast rights and sponsorships in association with its crewed landing, which it says would take place in the 2020s. But the money required to fund a robotic mission isn’t available from that revenue source yet. Hence, the organization is seeking an upfront investment in its work to get the money ready for development.
Composite image showing the size difference between Earth and Mars. Credit: NASA/Mars Exploration
Lansdorp said Mars One already underwent an angel investment round, and the organization is now in touch with an institutional group connected to an “institutional fund”, which would also attract money from other investors. Negotiations are ongoing, so the name is not disclosed publicly yet.
The goal is to have this investment group fund the robotic mission and the crewed one. The investor’s financial return would come from the eventual broadcasting and sponsorship revenues.
Aims of the robotic mission include testing some of the technologies that the crew would later take advantage of, such as extracting water from the planet’s underground and testing solar panels on the Martian surface.
Panorama of the Opportunity rover's view near the summit of Cape Tribulation on Mars in January 2015. Credit: NASA/JPL-Caltech/Stu Atkinson
As the Opportunity rover struggles with ongoing problems to its Flash memory, the plucky Martian machine — almost at its 11th anniversary of operations on the Red Planet — has reached the summit of a crater rim, providing spectacular views of the area below.
The Jet Propulsion Laboratory is readying a fix to the rover’s memory, which is required to store images overnight while the rover sleeps. Controllers are still getting the data by making daily downloads before the sleep period, but it is having an effect on operations.
“The fix for the flash memory requires a change to the rover’s flight software, so we are conducting extensive testing to be sure it will not lead to any unintended consequences for rover operations,” stated John Callas, project manager for Opportunity at the Jet Propulsion Laboratory.
The Opportunity rover views the peak of “Cape Tribulation” on Mars in January 2015. Credit: NASA/JPL-Caltech/Stu Atkinson
Computer World has a few details on the upcoming memory format. What’s worrying controllers is not so much the immense distance to the Red Planet — they are used to those sorts of procedures in this long mission — but more the danger of introducing a software update that could make the rover stop talking to Earth. So there are frequent simulations going on as NASA prepares a fix, which is reported to be taking place within a week if possible.
A rough panorama of the Opportunity rover’s surroundings on Mars based on three images taken on Sol 3,861 in December 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. Panorama: Elizabeth Howell
But Opportunity’s treks on Mars continue. The rover is now atop the Endeavour Crater’s rim at a spot nicknamed “Cape Tribulation”, named after one of the locations the explorer James Cook visited with HMS Endeavour during his New Zealand and Australia mission between 1769 and 1771.
This location is the highest point Opportunity reached during its 40-month exploration of Endeavour Crater. It’s sitting on a height roughly 440 feet (135 meters) above the plains and, after two lengthy drives Monday and Tuesday (Jan. 5 and Jan. 6) its odometer is currently at 25.8 miles (41.6 kilometers).
Opportunity’s next destination is called “Marathon Valley”, a spot that could have minerals soaked with water in the past (at least, according to pictures obtained from orbit). By the time the rover gets there, it should have passed a marathon’s worth of driving on the Red Planet.
We’ve seen volcanoes or geysers erupting on the moons of Io and Enceladus. Volcanic remnants remain on Mars and the Moon. But it’s tough for rovers to get inside these challenging environments.
So NASA’s Jet Propulsion Laboratory is trying out a new robot here on Earth to one day, they hope, get inside volcanoes elsewhere in the Solar System.
The series is called VolcanoBot. The first prototype was tested last year inside the the active Kilauea volcano in Hawaii, and a second is set for further work later this year.
As you can see in the picture below, VolcanoBot has a set of small wheels and a host of electronics inside. The goal is to create 3-D maps of the environments in which they roam. And early results are showing some promise, NASA noted in a press release: VolcanoBot discovered the fissure it was exploring did not completely close up, which is something they did not expect.
The Jet Propulsion Laboratory’s VolcanoBot 1 inside a lava tube at the Kilauea volcano in Hawaii. Credit: NASA/JPL-Caltech
“We don’t know exactly how volcanoes erupt. We have models but they are all very, very simplified. This project aims to help make those models more realistic,” stated Carolyn Parcheta, a NASA postdoctoral fellow at the Jet Propulsion Laboratory in California who is leading the research.
“In order to eventually understand how to predict eruptions and conduct hazard assessments, we need to understand how the magma is coming out of the ground,” she added. “This is the first time we have been able to measure it directly, from the inside, to centimeter-scale accuracy.”
The research will continue this year with VolcanoBot 2, which has less mass, less size and has an advanced “vison center” that can turn about.
Artist’s impression of the Cassini spacecraft making a close pass by Saturn’s inner moon Enceladus to study plumes from geysers that erupt from giant fissures in the moon’s southern polar region. Copyright 2008 Karl Kofoed/NASA. Click for full size version.
Parcheta’s research recently attracted the attention of visitors to National Geographic’s website, who voted her #2 in a list of “great explorers” on the Expedition Granted campaign.
Remember that this is early-stage research, with no missions outside of Earth yet assigned. But this is a small step — or roll, in this case — to better understanding how volcanoes work generally, whether on our own planet or other locations.
The James Webb Space Telescope, scheduled for launch in 2018 may be the first to be capable of detecting biomarker gasses in the atmospheres of extrasolar planets. When an exoplanet passes between its star and Earth, an event called a transit, light that has passed through the planet’s atmosphere can be detected from a vantage point near Earth. When light passes through the exoplanet’s atmosphere, some wavelengths are absorbed and others transmitted. By analyzing the transmitted light spectrum, astronomers can learn the composition of the planet’s atmosphere. Astrobiologists hope to find biomarker gasses indicating the metabolic waste products of life. The oxygen in Earth’s atmosphere is a waste product of photosynthesis in plants and bacteria. The Webb telescope may be capable of conducting this test for planets larger than Earth (super-earths) transiting small stars. Space telescopes capable of conducting such research on a larger scale have been delayed by budget cuts.
Credit: NASA
In the movie “Avatar”, we could tell at a glance that the alien moon Pandora was teeming with alien life. Here on Earth though, the most abundant life is not the plants and animals that we are familiar with. The most abundant life is simple and microscopic. There are 50 million bacterial organisms in a single gram of soil, and the world wide bacterial biomass exceeds that of all plants and animals. Microbes can grow in extreme environments of temperature, salinity, acidity, radiation, and pressure. The most likely form in which we will encounter life elsewhere in our solar system is microbial.
Astrobiologists need strategies for inferring the presence of alien microbial life or its fossilized remains. They need strategies for inferring the presence of alien life on the distant planets of other stars, which are too far away to explore with spacecraft in the foreseeable future. To do these things, they long for a definition of life, that would make it possible to reliably distinguish life from non-life.
Unfortunately, as we saw in the first installment of this series, despite enormous growth in our knowledge of living things, philosophers and scientists have been unable to produce such a definition. Astrobiologists get by as best they can with definitions that are partial, and that have exceptions. Their search is geared to the features of life on Earth, the only life we currently know.
In the first installment, we saw how the composition of terrestrial life influences the search for extraterrestrial life. Astrobiologists search for environments that once contained or currently contain liquid water, and that contain complex molecules based on carbon. Many scientists, however, view the essential features of life as having to do with its capacities instead of its composition.
In 1994, a NASA committee adopted a definition of life as a “self-sustaining chemical system capable of Darwinian evolution”, based on a suggestion by Carl Sagan. This definition contains two features, metabolism and evolution, that are typically mentioned in definitions of life.
Metabolism is the set of chemical processes by which living things actively use energy to maintain themselves, grow, and develop. According to the second law of thermodynamics, a system that doesn’t interact with its external environment will become more disorganized and uniform with time. Living things build and maintain their improbable, highly organized state because they harness sources of energy in their external environment to power their metabolism.
Plants and some bacteria use the energy of sunlight to manufacture larger organic molecules out of simpler subunits. These molecules store chemical energy that can later be extracted by other chemical reactions to power their metabolism. Animals and some bacteria consume plants or other animals as food. They break down complex organic molecules in their food into simpler ones, to extract their stored chemical energy. Some bacteria can use the energy contained in chemicals derived from non-living sources in the process of chemosynthesis.
In a 2014 article in Astrobiology, Lucas John Mix, a Harvard evolutionary biologist, referred to the metabolic definition of life as Haldane Life after the pioneering physiologist J. B. S. Haldane. The Haldane life definition has its problems. Tornadoes and vorticies like Jupiter’s Great Red Spot use environmental energy to sustain their orderly structure, but aren’t alive. Fire uses energy from its environment to sustain itself and grow, but isn’t alive either.
Despite its shortcomings, astrobiologists have used Haldane definition to devise experiments. The Viking Mars landers made the only attempt so far to directly test for extraterrestrial life, by detecting the supposed metabolic activities of Martian microbes. They assumed that Martian metabolism is chemically similar to its terrestrial counterpart.
One experiment sought to detect the metabolic breakdown of nutrients into simpler molecules to extract their energy. A second aimed to detect oxygen as a waste product of photosynthesis. A third tried to show the manufacture of complex organic molecules out of simpler subunits, which also occurs during photosynthesis. All three experiments seemed to give positive results, but many researchers believe that the detailed findings can be explained without biology, by chemical oxidizing agents in the soil.
In 1976, two Viking spacecraft landed on Mars. The image is of a model of the Viking lander, along with astronomer and pioneering astrobiologist Carl Sagan. Each lander was equipped with life detection experiments designed to detect life based on its metabolic activities. These activities were assumed to be chemically similar to those of Earthly organisms. The three experiments included: 1) The labeled release experiment, in which radioactively labeled organic nutrients were added to Martian soil. If organisms were present, it was assumed that their metabolism would involve breaking down the nutrients for their energy content and releasing labeled carbon dioxide as a waste product. 2) The gas exchange experiment, in which Martian soil was provided with nutrients and light and monitored for the release of oxygen. On Earth, organisms that capture the energy of sunlight through the process of photosynthesis, like plants and some bacteria, release oxygen as a waste product. 3) The pyrolytic release experiment, in which Martian soil was placed in a chamber with radioactively labeled carbon dioxide. If there were organisms in the soil that photosynthesized like those on Earth, their metabolic processes would take up the gas and use the energy of sunlight to manufacture more complex organic molecules. Radioactive carbon would be given off when those more complex molecules were broken down by heating the sample. All three experiments produced what seemed like positive results. However, most scientists rejected this interpretation because the details of many of the results could be explained by supposing that there were chemical oxidizing agents in the soil instead of life, and because Viking failed to detect organic materials in Martian soil. This interpretation, especially for the labeled release experiment, remains controversial to this day and may need to be revisited based on recent findings. Credits: NASA/Jet Propulsion Laboratory, Caltech
Some of the Viking results remain controversial to this day. At the time, many researchers felt that the failure to find organic materials in Martian soil ruled out a biological interpretation of the metabolic results. The more recent finding that Martian soil actually does contain organic molecules that might have been destroyed by perchlorates during the Viking analysis, and that liquid water was once abundant on the surface of Mars lend new plausibility to the claim that Viking may have actually succeeded in detecting life. By themselves, though, the Viking results didn’t prove that life exists on Mars nor rule it out.
Most of the methane in Earth’s atmosphere is released by living organisms or their remains. Subterranean bacterial ecosystems that use chemosynthesis as a source of energy are common, and they produce methane as a metabolic waste product. Unfortunately, there are also non-biological geochemical processes that can produce methane. So, once more, Martian methane is frustratingly ambiguous as a sign of life.
Extrasolar planets orbiting other stars are far too distant to visit with spacecraft in the foreseeable future. Astrobiologists still hope to use the Haldane definition to search for life on them. With near future space telescopes, astronomers hope to learn the composition of the atmospheres of these planets by analyzing the spectrum of light wavelengths reflected or transmitted by their atmospheres. The James Webb Space Telescope scheduled for launch in 2018, will be the first to be useful in this project. Astrobiologists want to search for atmospheric biomarkers; gases that are metabolic waste products of living organisms.
Once more, this quest is guided by the only example of a life-bearing planet we currently have; Earth. About 21% of our home planet’s atmosphere is oxygen. This is surprising because oxygen is a highly reactive gas that tends to enter into chemical combinations with other substances. Free oxygen should quickly vanish from our air. It remains present because the loss is constantly being replaced by plants and bacteria that release it as a metabolic waste product of photosynthesis.
Traces of methane are present in Earth’s atmosphere because of chemosynthetic bacteria. Since methane and oxygen react with one another, neither would stay around for long unless living organisms were constantly replenishing the supply. Earth’s atmosphere also contains traces of other gases that are metabolic byproducts.
In general, living things use energy to maintain Earth’s atmosphere in a state far from the thermodynamic equilibrium it would reach without life. Astrobiologists would suspect any planet with an atmosphere in a similar state of harboring life. But, as for the other cases, it would be hard to completely rule out non-biological possibilities.
Besides metabolism, the NASA committee identified evolution as a fundamental ability of living things. For an evolutionary process to occur there must be a group of systems, where each one is capable of reliably reproducing itself. Despite the general reliability of reproduction, there must also be occasional random copying errors in the reproductive process so that the systems come to have differing traits. Finally, the systems must differ in their ability to survive and reproduce based on the benefits or liabilities of their distinctive traits in their environment. When this process is repeated over and over again down the generations, the traits of the systems will become better adapted to their environment. Very complex traits can sometimes evolve in a step-by-step fashion.
Mix named this the Darwin life definition, after the nineteenth century naturalist Charles Darwin, who formulated the theory of evolution. Like the Haldane definition, the Darwin life definition has important shortcomings. It has trouble including everything that we might think of as alive. Mules, for example, can’t reproduce, and so, by this definition, don’t count as being alive.
Despite such shortcomings, the Darwin life definition is critically important, both for scientists studying the origin of life and astrobiologists. The modern version of Darwin’s theory can explain how diverse and complex forms of life can evolve from some initial simple form. A theory of the origin of life is needed to explain how the initial simple form acquired the capacity to evolve in the first place.
The chemical systems or life forms found on other planets or moons in our solar system might be so simple that they are close to the boundary between life and non-life that the Darwin definition establishes. The definition might turn out to be vital to astrobiologists trying to decide whether a chemical system they have found really qualifies as a life form. Biologists still don’t know how life originated. If astrobiologists can find systems near the Darwin boundary, their findings may be pivotally important to understanding the origin of life.
Can astrobiologists use the Darwin definition to find and study extraterrestrial life? It’s unlikely that a visiting spacecraft could detect to process of evolution itself. But, it might be capable of detecting the molecular structures that living organisms need in order to take part in an evolutionary process. Philosopher Mark Bedau has proposed that a minimal system capable of undergoing evolution would need to have three things: 1) a chemical metabolic process, 2) a container, like a cell membrane, to establish the boundaries of the system, and 3) a chemical “program” capable of directing the metabolic activities.
Here on Earth, the chemical program is based on the genetic molecule DNA. Many origin-of-life theorists think that the genetic molecule of the earliest terrestrial life forms may have been the simpler molecule ribonucleic acid (RNA). The genetic program is important to an evolutionary process because it makes the reproductive copying process stable, with only occasional errors.
Both DNA and RNA are biopolymers; long chainlike molecules with many repeating subunits. The specific sequence of nucleotide base subunits in these molecules encodes the genetic information they carry. So that the molecule can encode all possible sequences of genetic information it must be possible for the subunits to occur in any order.
Steven Benner, a computational genomics researcher, believes that we may be able to develop spacecraft experiments to detect alien genetic biopolymers. He notes that DNA and RNA are very unusual biopolymers because changing the sequence in which their subunits occur doesn’t change their chemical properties. It is this unusual property that allows these molecules to be stable carriers of any possible genetic code sequence.
DNA and RNA are both polyelectrolytes; molecules with regularly repeating areas of negative electrical charge. Benner believes that this is what accounts for their remarkable stability. He thinks that any alien genetic biopolymer would also need to be a polyelectrolyte, and that chemical tests could be devised by which a spacecraft might detect such polyelectrolyte molecules. Finding the alien counterpart of DNA is a very exciting prospect, and another piece to the puzzle of identifying alien life.
Deoxyribonucleic acid (DNA) is the genetic material for all known life on Earth. DNA is a biopolymer consisting of a string of subunits. The subunits consist of nucleotide base pairs containing a purine (adenine A, or guanine G) and a pyrimidine (thymine T, or cytosine C). DNA can contain nucleotide base pairs in any order without its chemical properties changing. This property is rare in biopolymers, and makes it possible for DNA to encode genetic information in the sequence of its base pairs. This stability is due to the fact that each base pair contains phosphate groups (consisting of phosphorus and oxygen atoms) on the outside with a net negative charge. These repeated negative charges make DNA a polyelectrolyte. Computational genomics researcher Steven Benner has hypothesized that alien genetic material will also be a polyelectrolyte biopolymer, and that chemical tests could therefore be devised to detect alien genetic molecules. Credit: Zephyris
In 1996 President Clinton, made a dramatic announcement of the possible discovery of life on Mars. Clinton’s speech was motivated by the findings of David McKay’s team with the Alan Hills meteorite. In fact, the McKay findings turned out to be just one piece to the larger puzzle of possible Martian life. Unless an alien someday ambles past our waiting cameras, the question of whether or not extraterrestrial life exists is unlikely to be settled by a single experiment or a sudden dramatic breakthrough. Philosophers and scientists don’t have a single, sure-fire definition of life. Astrobiologists consequently don’t have a single sure-fire test that will settle the issue. If simple forms of life do exist on Mars, or elsewhere in the solar system, it now seems likely that that fact will emerge gradually, based on many converging lines of evidence. We won’t really know what we’re looking for until we find it.
S. Tirard, M. Morange, and A. Lazcano, (2010), The definition of life: A brief history of an elusive scientific endeavor, Astrobiology, 10(10):1003-1009.
Artist's conception of the futuristic Hypersonic Inflatable Aerodynamic Decelerator (HIAD) entering the atmosphere of Mars. Credit: NASA
Assuming we can get humans all the way to Mars, how the heck do we land them on the Red Planet? The challenge is the atmosphere of Mars is very thin, making parachutes tricky. Heavier payloads require unique ideas to get them on the surface, such as the wild ride we saw for the Curiosity rover.
Since humans and their cargo would have much more mass, one of the ideas NASA is exploring is something called the Hypersonic Inflatable Aerodynamic Decelerator (HIAD). And here’s the surprising thing — it looks a little like those donut toys that small children play with.
“In a real spacecraft, a connected stack of donut rings would be inflated before entering a planet’s atmosphere to slow the vehicle for landing,” NASA wrote in an update last June. “The spaceship would look a lot like a giant cone with the space donuts assembled, similar to a child’s stacking ring toy. The stacked-cone concept would allow NASA to land heavier payloads to the surface of the planet than is currently possible, and could eventually be used to deliver crews.”
The concept has been heavily highlighted in the media this week, but what is less spoken about is the uncertainty of the project. The June update came after NASA performed structural testing on a prototype in NASA Armstrong’s Flight Loads Laboratory for seven months in 2013 and 2014. And that was the end of a three-year project under NASA’s Game-Changing Technology program.
What project officials hope for is that they will win a proposal to do more work in 2016. If that works out, they’ll perform more testing on the project. NASA says the technology could be available for use as soon as 2020, but we’ll have to see how things work out.
The principal investigator for its materials and structure is Anthony Calomino, who is with NASA Langley. You can find more information on HIAD on this website.
The Hypersonic Inflatable Aerodynamic Decelerator prototype undergoes structural tests at NASA Armstrong’s Flight Loads Laboratory in this undated photo. Tests took place in 2013 and 2014. Credit: NASA
In December, 2014 researchers in the Mars Science Laboratory Project announced that they had made the first definitive detection of organic materials on the surface of Mars. The sample was taken on May 19, 2013 from a rock that mission controllers named “Cumberland”. The Curiosity Mars rover drilled a hole 1.6 cm wide and 6.6 cm deep in the Martian rock. Powered rock from the hole was delivered to the rover’s Sample Analysis at Mars (SAM) instrument for analysis. The scientists drew their conclusions only after months of careful analysis. The identity and complexity of the organic substances remains uncertain, because they may have been altered by perchlorates that were also present in the rock, when the material was heated for analysis. The Viking Mars landers of 1976 had earlier failed to detect organic materials on Mars.
Credits: NASA/Jet Propulsion Laboratory, Caltech
How can astrobiologists find extraterrestrial life? In everyday life, we usually don’t have any problem telling that a dog or a rosebush is a living thing and a rock isn’t. In the climatic scene of the movie ‘Europa Report’ we can tell at a glance that the multi-tentacled creature discovered swimming in the ocean of Jupiter’s moon Europa is alive, complicated, and quite possibly intelligent.
But unless something swims, walks, crawls, or slithers past the cameras of a watching spacecraft, astrobiologists face a much tougher job. They need to devise tests that will allow them to infer the presence of alien microbial life from spacecraft data. They need to be able to recognize fossil traces of past alien life. They need to be able to determine whether the atmospheres of distant planets circling other stars contain the tell-tale traces of unfamiliar forms of life. They need ways to infer the presence of life from knowledge of its properties. A definition of life would tell them what those properties are, and how to look for them. This is the first of a two part series exploring how our concept of life influences the search for extraterrestrial life.
What is it that sets living things apart? For centuries, philosophers and scientists have sought an answer. The philosopher Aristotle (384-322 BC) devoted a great deal of effort to dissecting animals and studying living things. He supposed that they had distinctive special capacities that set them apart from things that aren’t alive. Inspired by the mechanical inventions of his times, the Renaissance philosopher Rene Descartes (1596-1650) believed that living things were like clockwork machines, their special capacities deriving from the way their parts were organized.
In 1944, the physicist Erwin Schrödinger (1887-1961) wrote What is Life? In it, he proposed that the fundamental phenomena of life, including even how parents pass on their traits to their offspring, could be understood by studying the physics and chemistry of living things. Schrödinger’s book was an inspiration to the science of molecular biology.
Living organisms are made of large complicated molecules with backbones of linked carbon atoms. Molecular biologists were able to explain many of the functions of life in terms of these organic molecules and the chemical reactions they undergo when dissolved in liquid water. In 1955 James Watson and Francis Crick discovered the structure of deoxyribonucleic acid (DNA) and showed how it could be the storehouse of hereditary information passed from parent to offspring.
While all this research and theorizing has vastly increased our understanding of life, it hasn’t produced a satisfactory definition of life; a definition that would allow us to reliably distinguish things that are alive from things that aren’t. In 2012 the philosopher Edouard Mahery argued that coming up with a single definition of life was both impossible and pointless. Astrobiologists get by as best they can with definitions that are partial, and that have exceptions. Their search is conditioned by our knowledge of the specific features of life on Earth; the only life we currently know.
Here on Earth, living things are distinctive in their chemical composition. Besides carbon, the elements hydrogen, nitrogen, oxygen, phosphorus, and sulfur are particularly important to the large organic molecules that make up terrestrial life. Water is a necessary solvent. Since we don’t know for sure what else might be possible, the search for extraterrestrial life typically assumes its chemical composition will be similar to that of life on Earth.
Making use of that assumption, astrobiologists assign a high priority to the search for water on other celestial bodies. Spacecraft evidence has proven that Mars once had bodies of liquid water on its surface. Determining the history and extent of this water is a central goal of Mars exploration. Astrobiologists are excited by evidence of subsurface oceans of water on Jupiter’s moon Europa, Saturn’s moon Enceladus, and perhaps on other moons or dwarf planets. But while the presence of liquid water implies conditions appropriate for Earth-like life, it doesn’t prove that such life exists or has ever existed. Jupiter’s icy moon Europa appears to host liquid water, an essential condition for life as we know it on Earth. Its surface is covered with a crust of water ice. The Voyager and Galileo spacecraft have provided evidence that under this icy crust, there is an ocean of saltwater, containing more liquid water than all the oceans of Earth. Europa’s interior is heated by gravitational tidal forces exerted by giant Jupiter. This heat energy may drive volcanism, hydrothermal vents, and the production of chemical energy sources that living things could make use of. Interaction between materials from Europa’s surface and the ocean environment beneath could make available carbon and other chemical elements essential for Earth-like life. Credits: NASA/Jet Propulsion Laboratory, SETI Institute
Organic chemicals are necessary for Earth-like life, but, as for water, their presence doesn’t prove that life exists, because organic materials can also be formed by non-biological processes. In 1976, NASA’s two Viking landers were the first spacecraft to make fully successful landings on Mars. They carried an instrument; called the gas chromatograph-mass spectrometer, that tested the soil for organic molecules.
Even without life, scientists expected to find some organic materials in the Martian soil. Organic materials formed by non-biological processes are found in carbonaceous meteorites, and some of these meteorites should have fallen on Mars. They were surprised to find nothing at all. At the time, the failure to find organic molecules was considered a major blow to the possibility of life on Mars.
In 2008, NASA’s Phoenix lander discovered an explanation of why Viking didn’t detect organic molecules. If found that the Martian soil contains perchlorates. Containing oxygen and chlorine, perchlorates are oxidizing agents that can break down organic material. While perchlorates and organic molecules could coexist in Martian soil, scientists determined that heating the soil for the Viking analysis would have caused the perchlorates to destroy any organic material it contained. Martian soil might contain organic materials, after all.
At a news briefing in December 2014, NASA announced that an instrument carried on board the Curiosity Mars rover had succeeded in detected simple organic molecules on Mars for the first time. Researchers believe it is possible that the molecules detected may be breakdown products of more complex organic molecules that were broken down by perchlorates during the process of analysis. In 1996 a team of scientists lead by Dr. David McKay of NASA’s Johnson Space Center announced possible evidence of life on Mars. The evidence came from their studies of a Martian meteorite found in Antarctica, called Alan Hills 84001. The researchers found chemical and physical traces of possible life including carbonate globules that resemble terrestrial nanobacteria (electron micrograph shown) and polycyclic aromatic hydrocarbons. In terrestrial rock, the chemical traces would be considered breakdown products of bacterial life. The findings became the subject of controversy as non-biological explanations for the findings were found. Today, they are no longer regarded as definitive evidence of Martian life. Credits: NASA Johnson Space Center
The chemical make-up of terrestrial life has also guided the search for traces of life in Martian meteorites. In 1996 a team of investigators lead by David McKay of the Johnson Space Center in Houston reported evidence that a Martian meteorite found at Alan Hills in Antarctica in 1984 contained chemical and physical evidence of past Martian life.
There have since been similar claims about other Martian meteorites. But, non-biological explanations for many of the findings have been proposed, and the whole subject has remained embroiled in controversy. Meteorites have not so far yielded the kind of evidence needed to prove the existence of extraterrestrial life beyond reasonable doubt.
Following Aristotle, most scientists prefer to define life in terms of its capacities rather than its composition. In the second installment, we will explore how our understanding of life’s capacities has influenced the search for extraterrestrial life.
S. Tirard, M. Morange, and A. Lazcano, (2010), The definition of life: A brief history of an elusive scientific endeavor, Astrobiology, 10(10):1003-1009.
