The night sky, is the night sky, is the night sky. The constellations you learned as a child are the same constellations that you see today. Ancient people recognized these same constellations. Oh sure, they might not have had the same name for it, but essentially, we see what they saw.
But when you see animations of galaxies, especially as they come together and collide, you see the stars buzzing around like angry bees. We know that the stars can have motions, and yet, we don’t see them moving?
How fast are they moving, and will we ever be able to tell?
Stars, of course, do move. It’s just that the distances are so great that it’s very difficult to tell. But astronomers have been studying their position for thousands of years. Tracking the position and movements of the stars is known as astrometry.
We trace the history of astrometry back to 190 BC, when the ancient Greek astronomer Hipparchus first created a catalog of the 850 brightest stars in the sky and their position. His student Ptolemy followed up with his own observations of the night sky, creating his important document: the Almagest.
Printed rendition of a geocentric cosmological model from Cosmographia, Antwerp, 1539. Credit: Wikipedia Commons/Fastfission
In the Almagest, Ptolemy laid out his theory for an Earth-centric Universe, with the Moon, Sun, planets and stars in concentric crystal spheres that rotated around the planet. He was wrong about the Universe, of course, but his charts and tables were incredibly accurate, measuring the brightness and location of more than 1,000 stars.
A thousand years later, the Arabic astronomer Abd al-Rahman al-Sufi completed an even more detailed measurement of the sky using an astrolabe.
One of the most famous astronomers in history was the Danish Tycho Brahe. He was renowned for his ability to measure the position of stars, and built incredibly precise instruments for the time to do the job. He measured the positions of stars to within 15 to 35 arcseconds of accuracy. Just for comparison, a human hair, held 10 meters away is an arcsecond wide.
Also, I’m required to inform you that Brahe had a fake nose. He lost his in a duel, but had a brass replacement made.
In 1807, Friedrich Bessel was the first astronomer to measure the distance to a nearby star 61 Cygni. He used the technique of parallax, by measuring the angle to the star when the Earth was on one side of the Sun, and then measuring it again 6 months later when the Earth was on the other side.
With parallax technique, astronomers observe object at opposite ends of Earth’s orbit around the Sun to precisely measure its distance. Credit: Alexandra Angelich, NRAO/AUI/NSF.
Over the course of this period, this relatively closer star moves slightly back and forth against the more distant background of the galaxy.
And over the next two centuries, other astronomers further refined this technique, getting better and better at figuring out the distance and motions of stars.
But to really track the positions and motions of stars, we needed to go to space. In 1989, the European Space Agency launched their Hipparcos mission, named after the Greek astronomer we talked about earlier. Its job was to measure the position and motion of the nearby stars in the Milky Way. Over the course of its mission, Hipparcos accurately measured 118,000 stars, and provided rough calculations for another 2 million stars.
That was useful, and astronomers have relied on it ever since, but something better has arrived, and its name is Gaia.
Launched in December 2013, the European Space Agency’s Gaia in is in the process of mapping out a billion stars in the Milky Way. That’s billion, with a B, and accounts for about 1% of the stars in the galaxy. The spacecraft will track the motion of 150 million stars, telling us where everything is going over time. It will be a mind bending accomplishment. Hipparchus would be proud.
With the most precise measurements, taken year after year, the motions of the stars can indeed be calculated. Although they’re not enough to see with the unaided eye, over thousands and tens of thousands of years, the positions of the stars change dramatically in the sky.
The familiar stars in the Big Dipper, for example, look how they do today. But if you go forward or backward in time, the positions of the stars look very different, and eventually completely unrecognizable.
When a star is moving sideways across the sky, astronomers call this “proper motion”. The speed a star moves is typically about 0.1 arc second per year. This is almost imperceptible, but over the course of 2000 years, for example, a typical star would have moved across the sky by about half a degree, or the width of the Moon in the sky.
A 20 year animation showing the proper motion of Barnard’s Star. Credit: Steve Quirk, images in the Public Domain.
The star with the fastest proper motion that we know of is Barnard’s star, zipping through the sky at 10.25 arcseconds a year. In that same 2000 year period, it would have moved 5.5 degrees, or about 11 times the width of your hand. Very fast.
When a star is moving toward or away from us, astronomers call that radial velocity. They measure this by calculating the doppler shift. The light from stars moving towards us is shifted towards the blue side of the spectrum, while stars moving away from us are red-shifted.
Between the proper motion and redshift, you can get a precise calculation for the exact path a star is moving in the sky.
Credit: ESA/ATG medialab
We know, for example, that the dwarf star Hipparcos 85605 is moving rapidly towards us. It’s 16 light-years away right now, but in the next few hundred thousand years, it’s going to get as close as .13 light-years away, or about 8,200 times the distance from the Earth to the Sun. This won’t cause us any direct effect, but the gravitational interaction from the star could kick a bunch of comets out of the Oort cloud and send them down towards the inner Solar System.
The motions of the stars is fairly gentle, jostling through gravitational interactions as they orbit around the center of the Milky Way. But there are other, more catastrophic events that can make stars move much more quickly through space.
When a binary pair of stars gets too close to the supermassive black hole at the center of the Milky Way, one can be consumed by the black hole. The other now has the velocity, without the added mass of its companion. This gives it a high-velocity kick. About once every 100,000 years, a star is kicked right out of the Milky Way from the galactic center.
A rogue star being kicked out of a galaxy. Credit: NASA, ESA, and G. Bacon (STScI)
Another situation can happen where a smaller star is orbiting around a supermassive companion. Over time, the massive star bloats up as supergiant and then detonates as a supernova. Like a stone released from a sling, the smaller star is no longer held in place by gravity, and it hurtles out into space at incredible speeds.
Astronomers have detected these hypervelocity stars moving at 1.1 million kilometers per hour relative to the center of the Milky Way.
All of the methods of stellar motion that I talked about so far are natural. But can you imagine a future civilization that becomes so powerful it could move the stars themselves?
In 1987, the Russian astrophysicist Leonid Shkadov presented a technique that could move a star over vast lengths of time. By building a huge mirror and positioning it on one side of a star, the star itself could act like a thruster.
An example of a stellar engine using a mirror and a Dyson Swarm. Credit: Vedexent at English Wikipedia (CC BY-SA 3.0)
Photons from the star would reflect off the mirror, imparting momentum like a solar sail. The mirror itself would be massive enough that its gravity would attract the star, but the light pressure from the star would keep it from falling in. This would create a slow but steady pressure on the other side of the star, accelerating it in whatever direction the civilization wanted.
Over the course of a few billion years, a star could be relocated pretty much anywhere a civilization wanted within its host galaxy.
This would be a true Type III Civilization. A vast empire with such power and capability that they can rearrange the stars in their entire galaxy into a configuration that they find more useful. Maybe they arrange all the stars into a vast sphere, or some kind of geometric object, to minimize transit and communication times. Or maybe it makes more sense to push them all into a clean flat disk.
Amazingly, astronomers have actually gone looking for galaxies like this. In theory, a galaxy under control by a Type III Civilization should be obvious by the wavelength of light they give off. But so far, none have turned up. It’s all normal, natural galaxies as far as we can see in all directions.
For our short lifetimes, it appears as if the sky is frozen. The stars remain in their exact positions forever, but if you could speed up time, you’d see that everything is in motion, all the time, with stars moving back and forth, like airplanes across the sky. You just need to be patient to see it.
The Five-hundred-metre Aperture Spherical Telescope (FAST) has just finished construction in the southwestern province of Guizhou. Credit: FAST
Relax, its not a space station! And according to the Chinese government, it’s for entirely peaceful purposes. It’s known as the Five-hundred-meter Aperture Spherical Telescope (FAST), a massive array that just finished construction in the southerwestern province of Guizhou, China. Equivalent in size to over 20 football fields joined end to end, it is the world’s largest radio telescope – thus ending the Arecibo Observatory’s 53 year reign.
As part of China’s growing commitment to space exploration, the FAST telescope will spend the coming decades exploring space and assisting in the hunt for extraterrestrial life. And once it commences operations this coming September, the Chinese expect it will remain the global leader in radio astronomy for the next ten or twenty years.
In addition to being larger than the Arecibo Observatory (which measures 305 meters in diameter), the telescope is reportedly 10 times more sensitive than its closest competitor – the steerable 100-meter telescope near Bonn, Germany. What’s more, unlike Arecibo (which has a fixed spherical curvature), FAST is capable of forming a parabolic mirror. That will allow researchers a greater degree of flexibility.
The Chinese Academy of Sciences (CAS) has spent the past five years building the telesccope, to the tune of 1.2-billion-yuan (180 million U.S. dollars). As the deputy head of the National Astronomical Observation, which is overseen by the CAS, Zheng Xiaonian was present at the celebrations marking the completion of the massive telescope.
As he was paraphrased as saying by the Xinhua News Agency: “The project has the potential to search for more strange objects to better understand the origin of the universe and boost the global hunt for extraterrestrial life.” Zheng was also quoted as saying that he expects FAST to be the global leader in radio astronomy for the next 10 to 20 years.
The construction of this array has also been a source of controversy. To protect the telescope from radio interference, Chinese authorities built FAST in Guizhou province’s isolated Dawodang depression, directly into the mountainside. However, to ensure that no magnetic disruptions are nearby, roughly 9,000 people are being removed from their homes and rehoused in the neighboring counties of Pingtang and Luodian.
Li Yuecheng is the secretary-general of the Guizhou Provincial Committee, which is part of the Chinese People’s Political Consultative Conference (CPPCC). As he was quoted as saying by the Xinhua News Agency, the move comes with compensation:
“The proposal asked the government to relocate residents within 5 kilometers of the Five-hundred-meter Aperture Spherical Telescope, or FAST, to create a sound electromagnetic wave environment… Each of the involved residents will get 12,000 yuan (1,838 U.S. dollars) subsidy from the provincial reservoir and eco-migration bureau, and each involved ethnic minority household with housing difficulties will get 10,000 yuan subsidy from the provincial ethnic and religious committee.”
China’s recent forays into space include the Chang’e-3 moon lander, seen here by the Yutu moon rover. Credit: CNSA/SASTIND/Xinhua/Marco Di Lorenzo/Ken Kremer
In addition, the construction of this telescope is seen by some as part of a growing desire on behalf of China to press its interests in the geopolitical realm. For instance, in their 2016 Annual Report to Congress, the Department of Defense indicated that China is looking to develop its space capabilities to prevent adversaries from being able to use space-based assets in a crisis. As the report states:
“In parallel with its space program, China continues to develop a variety of counterspace capabilities designed to limit or to prevent the use of space-based assets by the [Peoples’ Liberation Army’s] adversaries during a crisis or conflict… Although China continues to advocate the peaceful use of outer space, the report also noted China would ‘secure its space assets to serve its national economic and social development, and maintain outer space security.'”
However, for others, FAST is merely the latest step in China’s effort to become a superpower in the all-important domain of space exploration and research. Their other ambitions include mounting a crewed mission to the Moon by 2036 and building a space station (for which work has already begun). In addition, FAST will enable China to take part in another major area of space research, which is the search for extra-terrestrial life.
For decades, countries like the United States have leading this search through efforts like the SETI Institute and the Nexus for Exoplanet System Science (NExSS). But with the completion of this array, China now has the opportunity to make significant contributions in the hunt for alien intelligence.
In the meantime, the CAS’ scientists will be debugging the telescope and conducting trials in preparation for its activation, come September. Once it is operational, it will assist in other areas of research as well, which will include conducting surveys of neutral hydrogen in the Milky Way and other galaxies, as well as detecting pulsars and gravitational waves.
The left image shows a mosaic of images of Titan taken by the Cassini spacecraft in near infrared light. Titan’s polar seas are visible as sunlight glints off of them. The right image is a radar image of Kraken Mare. Credit: NASA Jet Propulsion Laboratory.
Could there be life on Saturn’s large moon Titan? Asking the question forces astrobiologists and chemists to think carefully and creatively about the chemistry of life, and how it might be different on other worlds than it is on Earth. In February, a team of researchers from Cornell University, including chemical engineering graduate student James Stevenson, planetary scientist Jonathan Lunine, and chemical engineer Paulette Clancy, published a pioneering study arguing that cell membranes could form under the exotic chemical conditions present on this remarkable moon.
In many ways, Titan is Earth’s twin. It’s the second largest moon in the solar system and bigger than the planet Mercury. Like Earth, it has a substantial atmosphere, with a surface atmospheric pressure a bit higher than Earth’s. Besides Earth, Titan is the only object in our solar system known to have accumulations of liquid on its surface. NASA’s Cassini space probe discovered abundant lakes and even rivers in Titan’s polar regions. The largest lake, or sea, called Kraken Mare, is larger than Earth’s Caspian Sea. Researchers know from both spacecraft observations and laboratory experiments that Titan’s atmosphere is rich in complex organic molecules, which are the building blocks of life.
All these features might make it seem as though Titan is tantalizingly suitable for life. The name ‘Kraken’, which refers to a legendary sea monster, fancifully reflects the eager hopes of astrobiologists. But, Titan is Earth’s alien twin. Being almost ten times further from the sun than Earth is, its surface temperature is a frigid -180 degrees Celsius. Liquid water is vital to life as we know it, but on Titan’s surface all water is frozen solid. Water ice takes on the role that silicon-containing rock does on Earth, making up the outer layers of the crust.
The liquid that fills Titan’s lakes and rivers is not water, but liquid methane, probably mixed with other substances like liquid ethane, all of which are gases here on Earth. If there is life in Titan’s seas, it is not life as we know it. It must be an alien form of life, with organic molecules dissolved in liquid methane instead of liquid water. Is such a thing even possible?
The Cornell team took up one key part of this challenging question by investigating whether cell membranes can exist in liquid methane. Every living cell is, essentially, a self-sustaining network of chemical reactions, contained within bounding membranes. Scientists think that cell membranes emerged very early in the history of life on Earth, and their formation might even have been the first step in the origin of life.
Here on Earth, cell membranes are as familiar as high school biology class. They are made of large molecules called phospholipids. Each phospholipid molecule has a ‘head’ and a ‘tail’. The head contains a phosphate group, with a phosphorus atom linked to several oxygen atoms. The tail consists of one or more strings of carbon atoms, typically 15 to 20 atoms long, with hydrogen atoms linked on each side. The head, due to the negative charge of its phosphate group, has an unequal distribution of electrical charge, and we say that it is polar. The tail, on the other hand, is electrically neutral.
Here on Earth, cell membranes are composed of phospholipid molecules dissolved in liquid water. A phospholipid has a backbone of carbon atoms (gray), and also contains hydrogen (sky blue), phosphorus (yellow), oxygen (red), and nitrogen (blue). Due to the positive charge associated with the nitrogen containing choline group, and the negative charge associated with the phosphate group, the head is polar, and attracts water. It is therefore hydrophilic. The hydrocarbon tail is electrically neutral and hydrophobic. The structure of a cell membrane is due these electrical properties of phospholipids and water. The molecules form a double layer, with the hydrophilic heads facing outward, towards water, and the hydrophobic tails facing inward, towards one another. Credit: Ties van Brussel
These electrical properties determine how phospholipid molecules will behave when they are dissolved in water. Electrically speaking, water is a polar molecule. The electrons in the water molecule are more strongly attracted to its oxygen atom than to its two hydrogen atoms. So, the side of the molecule where the two hydrogen atoms are has a slight positive charge, and the oxygen side has a small negative charge. These polar properties of water cause it to attract the polar head of the phospholipid molecule, which is said to be hydrophilic, and repel its nonpolar tail, which is said to be hydrophobic.
When phospholipid molecules are dissolved in water, the electrical properties of the two substances work together to cause the phospholipid molecules to organize themselves into a membrane. The membrane closes onto itself into a little sphere called a liposome. The phospholipid molecules form a bilayer two molecules thick. The polar hydrophilic heads face outward towards the water on both the inner and outer surface of the membrane. The hydrophobic tails are sandwiched between, facing each other. While the phospholipid molecules remain fixed in their layer, with their heads facing out and their tails facing in, they can still move around with respect to each other, giving the membrane the fluid flexibility needed for life.
Phospholipid bilayer membranes are the basis of all terrestrial cell membranes. Even on its own, a liposome can grow, reproduce and aid certain chemical reactions important to life, which is why some biochemists think that the formation of liposomes might have been the first step towards life. At any rate, the formation of cell membranes must surely been an early step in life’s emergence on Earth.
At the left, water, consisting of hydrogen (H) and oxygen (O), is a polar solvent. Oxygen attracts electrons more strongly than hydrogen does, giving the hydrogen side of the molecule a net positive charge and the oxygen side a net negative charge. The delta symbol ( ) indicates that the charge is partial, that is less than a full unit of positive or negative charge. At right, methane is a non-polar solvent, due to the symmetrical distribution of hydrogen atoms (H) around a central carbon atom (C). Credit: Jynto as modified by Paul Patton.
If some form of life exists on Titan, whether sea monster or (more likely) microbe, it would almost certainly need to have a cell membrane, just like every living thing on Earth does. Could phospholipid bilayer membranes form in liquid methane on Titan? The answer is no. Unlike water, the methane molecule has an even distribution of electrical charges. It lacks water’s polar qualities, and so couldn’t attract the polar heads of phospholipid molecule. This attraction is needed for the phospholipids to form an Earth-style cell membrane.
Experiments have been conducted where phospholipids are dissolved in non-polar liquids at Earthly room temperature. Under these conditions, the phospholipids form an ‘inside-out’ two layer membrane. The polar heads of the phospholipid molecules are at the center, attracted to one another by their electrical charges. The non-polar tails face outward on each side of the inside-out membrane, facing the non-polar solvent.
At left, phospholipids are dissolved in water, a polar solvent. They form a bilayer membrane, with their polar, hydrophilic heads facing outward towards water, and their hydrophobic tails facing each other. At right, when phospholipids are dissolved in a non-polar solvent at Earthly room temperature, they form an inside-out membrane, with the polar heads attracting one another, and the non-polar tails facing outwards towards the non-polar solvent. Based on figure 2 from Stevenson, Lunine, and Clancy (2015). Credit: Paul Patton
Could Titanian life have an inside out phospholipid membrane? The Cornell team concluded that this wouldn’t work, for two reasons. The first is that at the cryogenic temperatures of liquid methane, the tails of phospholipids become rigid, depriving any inside-out membrane that might form of the fluid flexibility needed for life. The second is that two key ingredients of phospholipids; phosphorus and oxygen, are probably unavailable in the methane lakes of Titan. In their search for Titanian cell membranes, the Cornell team needed to probe beyond the familiar realm of high school biology.
Although not composed of phospholipids, the scientists reasoned that any Titanian cell membrane would nevertheless be like the inside-out phospholipid membranes created in the lab. It would consist of polar molecules clinging together electrically in a solution of non-polar liquid methane. What molecules might those be? For answers the researchers looked to data from the Cassini spacecraft and from laboratory experiments that reproduced the chemistry of Titan’s atmosphere.
Titan’s atmosphere is known to have a very complex chemistry. It is made mostly of nitrogen and methane gas. When the Cassini spacecraft analyzed its composition using spectroscopy it found traces of a variety of compounds of carbon, nitrogen, and hydrogen, called nitriles and amines. Researchers have simulated the chemistry of Titan’s atmosphere in the lab by exposing mixtures of nitrogen and methane to sources of energy simulating sunlight on Titan. A stew of organic molecules called ‘tholins’ is formed. It consists of compounds of hydrogen and carbon, called hydrocarbons, as well as nitriles and amines.
The Cornell investigators saw nitriles and amines as potential candidates for their Titanian cell membranes. Both are polar molecules that might stick together to form a membrane in non-polar liquid methane due to the polarity of nitrogen containing groups found in both of them. They reasoned that candidate molecules must be much smaller than phospholipids, so that they could form fluid membranes at liquid methane temperatures. They considered nitriles and amines containing strings of between three and six carbon atoms. Nitrogen containing groups are called ‘azoto’ –groups, so the team named their hypothetical Titanian counterpart to the liposome the ‘azotosome’.
Synthesizing azotosomes for experimental study would have been difficult and expensive, because the experiments would need to be conducted at the cryogenic temperatures of liquid methane. But since the candidate molecules have been studied extensively for other reasons, the Cornell researchers felt justified in turning to the tools of computational chemistry to determine whether their candidate molecules could cohere as a flexible membrane in liquid methane. Computational models have been used successfully to study conventional phospholipid cell membranes.
Acrylonitrile has been identified as a possible basis for cell membranes in liquid methane on Titan. It is known to be present in Titan’s atmosphere at a concentration of 10 parts per million and has been produced in laboratory simulations of the effects of energy sources on Titan’s nitrogen-methane atmosphere. As a small polar molecule capable of dissolving in liquid methane, it is a candidate substance for the formation of cell membranes in an alternative biochemistry on Titan. Light blue: carbon atoms, dark blue: nitrogen atom, white: hydrogen atoms. Credit: Ben Mills as modified by Paul Patton. Polar acrylonitrile molecules align ‘head’ to ‘tail’ to form a membrane in non-polar liquid methane. Light blue: carbon atoms, dark blue: nitrogen atoms, white: hydrogen atoms. Credit: James Stevenson.
The group’s computational simulations showed that some candidate substances could be ruled out because they would not cohere as a membrane, would be too rigid, or would form a solid. Nevertheless, the simulations also showed that a number of substances would form membranes with suitable properties. One suitable substance is acrylonitrile, which Cassini showed is present in Titan’s atmosphere at 10 parts per million concentration. Despite the huge difference in temperature between cryogenic azotozomes and room temperature liposomes, the simulations showed them to exhibit strikingly similar properties of stability and response to mechanical stress. Cell membranes, then, are possible for life in liquid methane.
Computational chemistry simulations show that acrylonitrile and some other small polar nitrogen containing organic molecules are capable of forming ‘azotosomes’ when they are dissolved on liquid methane. Azotosomes are small membrane bounded spherules like the liposomes formed by phospholipids when they are dissolved in water. The simulations show that acrylonitrile azotosomes would be both stable and flexible in cryogenically cold liquid methane, giving them the properties they need to function as cell membranes for hypothetical Titanian life, or for life on any world with liquid methane on its surface. The azotosome shown is 9 nanometers in size, about the size of a virus. Light blue: carbon atoms, dark blue: nitrogen atoms, white: hydrogen atoms. Credit: James Stevenson.
The scientists from Cornell view their findings as nothing more than a first step towards showing that life in liquid methane is possible, and towards developing the methods that future spacecraft will need to search for it on Titan. If life is possible in liquid methane, the implications ultimately extend far beyond Titan.
When seeking conditions suitable for life in the galaxy, astronomers typically search for exoplanets within a star’s habitable zone, defined as the narrow range of distances over which a planet with an Earth-like atmosphere would have a surface temperature suitable for liquid water. If methane life is possible, then stars would also have a methane habitable zone, a region where methane could exist as a liquid on a planet or moon, making methane life possible. The number of habitable worlds in the galaxy would be greatly increased. Perhaps, on some worlds, methane life evolves into complex forms that we can scarcely imagine. Maybe some of them are even a bit like sea monsters.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
It’s no accident that Jupiter shares its name with the king of the gods. In addition to being the largest planet in our Solar System – with two and a half times the mass of all the other planets combined – it is also home to some of the largest moons of any Solar planet. Jupiter’s largest moons are known as the Galileans, all of which were discovered by Galileo Galilei and named in his honor.
They include Io, Europa, Ganymede, and Callisto, and are the Solar System’s fourth, sixth, first and third largest satellites, respectively. Together, they contain almost 99.999% of the total mass in orbit around Jupiter, and range from being 400,000 and 2,000,000 km from the planet. Outside of the Sun and eight planets, they are also among the most massive objects in the Solar System, with radii larger than any of the dwarf planets.
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.
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.
NASA's James Webb Space Telescope, scheduled for launch in Dec. 2021, will be capable of measuring the spectrum of the atmospheres of Earthlike exoplanets orbiting small stars.
Credit: NASA, Northrop Grumman
Astronomers and planetary scientists thought they knew how to find evidence of life on planets beyond our Solar System. But, a new study indicates that the moons of extrasolar planets may produce “false positives” adding an inconvenient element of uncertainty to the search.
More than 1,800 exoplanets have been confirmed to exist so far, with the count rising rapidly. About 20 of these are deemed potentially habitable. This is because they are only somewhat more massive than Earth, and orbit their parent stars at distances that might allow liquid water to exist.
Astronomers soon hope to be able to determine the composition of the atmospheres of such promising alien worlds. They can do this by analyzing the spectrum of light absorbed by them. For Earth-like worlds circling small stars, this challenging feat can be accomplished using NASA’s James Webb Space Telescope, scheduled for launch in 2018.
They thought they knew how to look for the signature of life. There are certain gases which shouldn’t exist together in an atmosphere that is in chemical equilibrium. Earth’s atmosphere contains lots of oxygen and trace amounts of methane. Oxygen shouldn’t exist in a stable atmosphere. As anyone with rust spots on their car knows, it has a strong tendency to combine chemically with many other substances. Methane shouldn’t exist in the presence of oxygen. When mixed, the two gases quickly react to form carbon dioxide and water. Without some process to replace it, methane would be gone from our air in a decade.
On Earth, both oxygen and methane remain present together because the supply is constantly replenished by living things. Bacteria and plants harvest the energy of sunlight in the process of photosynthesis. As part of this process water molecules are broken into hydrogen and oxygen, releasing free oxygen as a waste product. About half of the methane in Earth’s atmosphere comes from bacteria. The rest is from human activities, including the growing of rice, the burning of biomass, and the flatulence produced by the vast herds of cows and other ruminants maintained by our species.
By itself, finding methane in a planet’s atmosphere isn’t surprising. Many purely chemical processes can make it, and it is abundant in the atmospheres of the gas giant planets Jupiter, Saturn, Uranus, and Neptune, and on Saturn’s large moon Titan. Although oxygen alone is sometimes touted as a possible biomarker; its presence, by itself, isn’t rock solid evidence of life either. There are purely chemical processes that might make it on an alien planet, and we don’t yet know how to rule them out. Finding these two gases together, though, seems as close as one could get to “smoking gun” evidence for the activities of life.
A monkey wrench was thrown into this whole argument by an international team of investigators led by Dr. Hanno Rein of the Department of Environmental and Physical Sciences at the University of Toronto in Canada. Their results were published in the May, 2014 edition of the Proceedings of the National Academy of Sciences USA.
Suppose, they posited, that oxygen is present in the atmosphere of a planet, and methane is present separately in the atmosphere of a moon orbiting the planet. The team used a mathematical model to predict the light spectrum that might be measured by a space telescope near Earth for plausible planet-moon pairs. They found that the resulting spectra closely mimicked that of a single object whose atmosphere contained both gasses.
Unless the planet orbits one of the very nearest stars, they showed it wasn’t possible to distinguish a planet-moon pair from a single object using technology that will be available anytime soon. The team termed their results “inconvenient, but unavoidable…It will be possible to obtain suggestive clues indicative of possible inhabitation, but ruling out alternative explanations of these clues will probably be impossible for the foreseeable future.”
Extrasolar planet HD189733b rises from behind its star. Is there methane on this planet? Image Credit: ESA
The search for life is largely limited to the search for water. We look for exoplanets at the correct distances from their stars for water to flow freely on their surfaces, and even scan radiofrequencies in the “water hole” between the 1,420 MHz emission line of neutral hydrogen and the 1,666 MHz hydroxyl line.
When it comes to extraterrestrial life, our mantra has always been to “follow the water.” But now, it seems, astronomers are turning their eyes away from water and toward methane — the simplest organic molecule, also widely accepted to be a sign of potential life.
Astronomers at the University College London (UCL) and the University of New South Wales have created a powerful new methane-based tool to detect extraterrestrial life, more accurately than ever before.
In recent years, more consideration has been given to the possibility that life could develop in other mediums besides water. One of the most interesting possibilities is liquid methane, inspired by the icy moon Titan, where water is as solid as rock and liquid methane runs through the river valleys and into the polar lakes. Titan even has a methane cycle.
Astronomers can detect methane on distant exoplanets by looking at their so-called transmission spectrum. When a planet transits, the star’s light passes through a thin layer of the planet’s atmosphere, which absorbs certain wavelengths of the light. Once the starlight reaches Earth it will be imprinted with the chemical fingerprints of the atmosphere’s composition.
But there’s always been one problem. Astronomers have to match transmission spectra to spectra collected in the laboratory or determined on a supercomputer. And “current models of methane are incomplete, leading to a severe underestimation of methane levels on planets,” said co-author Jonathan Tennyson from UCL in a press release.
So Sergei Yurchenko, Tennyson and colleagues set out to develop a new spectrum for methane. They used supercomputers to calculate about 10 billion lines — 2,000 times bigger than any previous study. And they probed much higher temperatures. The new model may be used to detect the molecule at temperatures above that of Earth, up to 1,500 K.
“We are thrilled to have used this technology to significantly advance beyond previous models available for researchers studying potential life on astronomical objects, and we are eager to see what our new spectrum helps them discover,” said Yurchenko.
The tool has already successfully reproduced the way in which methane absorbs light in brown dwarfs, and helped correct our previous measurements of exoplanets. For example, Yurchenko and colleagues found that the hot Jupiter, HD 189733b, a well-studied exoplanet 63 light-years from Earth, might have 20 times more methane than previously thought.
The paper has been published in the Proceedings of the National Academy of Sciences and may be viewed here.
The Jamesburg Earth Station radio dish in Carmel, California will be used to send the Lone Signal messages to space. Image via Lone Signal.
Although scientists have been listening for years to search for indications of other sentient life in the Universe, just a few efforts have been made by humans to purposefully send out messages to the cosmos. Called METI (Messaging to Extraterrestrial Intelligence) or Active SETI (Search for Extraterrestrial Intelligence), these messages have so far been just one-time bursts of info – or “pulses in time” said Dr. Jacob Haqq-Misra.
Haqq-Misra is leading a team of scientists and entrepreneurs who are launching a new initiative called “Lone Signal” which will send the first continuous mass “hailing messages” out into space, starting later this month. They’ll be specifically targeting one star system, Gliese 526, which has been identified as a potentially habitable solar system.
And yes, the general public can participate.
“From the start we wanted to be an experiment where anyone on Earth could participate,” said Haqq-Misra during a press event on June 11, 2013, announcing the project.
“Our scientific goals are to discover sentient beings outside of our solar system,” said Lone Star co-founder Pierre Fabre, also speaking at the event. “But an important part of this project is to get people to look beyond themselves and their differences by thinking about what they would say to a different civilization. Lone Signal will allow people to do that.”
Lone Signal will be using the recommissioned radio dish at the Jamesburg Earth Station in Carmel, California, one of the dishes used to carry the Apollo Moon landings live to the world.
Timelapse of the Jamesburg Earth Station
Lone Signal will be sending two signals: one is a continuous wave (CW) signal, a hailing message that sends a slow binary broadcast to provide basic information about Earth and our Solar System using an encoding system created by astrophysicist and planetary scientist Michael W. Busch. The binary code is based on mathematical “first principles” which reflect established laws that, theoretically, are relatively constant throughout the universe; things like gravity and the structure of the hydrogen atom, etc.
“This hailing message is a language we think could be used to instigate communication,” said Haqq-Misra, “and is the most advanced binary coding currently in use.”
The second signal, embedded in the first signal, will be messages from the people of Earth.
Strength of various signals from Earth. Graph courtesy of Dr. Haqq-Misra.
Since Gliese 526 is 17.6 light years from Earth, the messages will be beamed to the coordinates of where the star will be in 17.6 years from now. Even though no planets have been found yet in this system, the Lone Signal team said they are confident planets exist there since missions like Kepler and Corot have found that most stars host multiple planets.
The Lone Signal team is allowing anyone with access to the internet to send the equivalent of one free text message or Twitter message — a 144-character text-based message — into space. The team said they want to have messages sent from people all around the world to provide messages that are “representative of humanity.”
Anything additional, like more messages, images, etc., will cost money, but those funds will help support the project.
“In effect we are doing our own Kickstarter and doing the crowdfunding on our own,” said Lone Signal CEO Jamie King. “Long Signal would not be possible without crowd sourcing support, which will be used for maintaining the millions of dollars in equipment, powering the dish, running the web portal and other critical tech that makes the project possible.”
If you want to be part of the project and be a “beamer” you can currently sign up at the Lone Signal website –which currently doesn’t have much information. But on June 18th their public site will go live and ‘beamers will be able to submit messages as well as:
• Share Beams / Track Beams – Once signed in, users can see how far their beam has traveled from Earth as well as share it with the beaming community.
• Dedicate Beams – Parents, friends and loved ones can dedicate a beam to others.
• Explore – The Explore section gives beamers current data on the Lone Signal beam, who is sending messages, from where on Earth, overall stats, etc.
• Blog / Twitter – Via their blog and Twitter, the Lone Signal science team and other contributors will be posting opinion articles on associated topics of interest as well as sharing the latest science news and updates.
One you submit your “beam” you’ll be able to “echo” it on your Facebook and Twitter accounts.
After a user sends their initial free message, Lone Signal will be offering paid credit packages for purchase that allow users to transmit and share longer messages as well as images using credits in the following USD price structure:
• $0.99 buys 4 credits.
• $4.99 buys 40 credits.
• $19.99 buys 400 credits.
• $99.99 buys 4000 credits.
Following the initial free message, each subsequent text-based message costs 1 credit. Image-based messages cost 3 credits.
The team said that each message will be sent as an individual packet of information and won’t be bunched with other messages.
While some scientists have indicated that sending messages out into space might pose a hazard by attracting unwanted attention from potentially aggressive extraterrestrial civilizations, Haqq-Misra thinks the benefits outweigh the potential hazards. In fact, he and his team have written a paper about the concept.
“We want to inspire passion for the space sciences in people young and old, encourage citizens of Earth to think about their role in the Universe, and inspire the next generation of scientists and astronauts,” said Lone Signal chief marketing officer Ernesto Qualizza. “We’re really excited to find out what people will want to say, and the science of METI allows people to do this – to think about more than their own backyard.”
In this new video, SETI founder Frank Drake and astronomer Jill Tarter about why the search of the cosmos is important and needed. Visit SETI online to learn more about the search for signals of extraterrestrial life using radio telescopes on Earth and how you can help.
