Posted on by Matt Williams

Researchers Just Scanned 14 Worlds From the Kepler Mission for “Technosignatures”, Evidence of Advanced Civilizations

A team of astronomers from UCLA searched for "technosignatures" in the Kepler field data. Credit and Copyright: Danielle Futselaar

When it comes to looking for life on extra-solar planets, scientists rely on what is known as the “low-hanging fruit” approach. In lieu of being able to observe these planets directly or up close, they are forced to look for “biosignatures” – substances that indicate that life could exist there. Given that Earth is the only planet (that we know of) that can support life, these include carbon, oxygen, nitrogen and water.

However, while the presence of these elements are a good way of gauging “habitability”, they are not necessarily indications that extra-terrestrial civilizations exist. Hence why scientists engaged in the Search for Extra-Terrestrial Intelligence (SETI) also keep their eyes peeled for “technosignatures”. Targeting the Kepler field, a team of scientists recently conducted a study that examined 14 planetary systems for indications of intelligent life.

The study, titled “A search for technosignatures from 14 planetary systems in the Kepler field with the Green Bank Telescope at 1.15-1.73 GHz“, recently appeared online and is being reviewed for publication by The Astronomical Journal. The team was led by Jean-Luc Margot, the Chair of the UCLA Department of Earth, Planetary, and Space Sciences (UCLA EPSS) and a Professor with UCLA’s Department of Physics and Astronomy.

The Green Bank Telescope is the world’s largest, fully-steerable telescope, which is currently being used in a new SETI (Search for Extraterrestrial Intelligence) attempt to look for possible alien radio signals from Tabby’s Star. Credit: NRAO/AUI/NSF

In addition to Margot, the team consisted of 15 graduate and undergraduate students from UCLA and a postdoctoral researcher from the Green Bank Observatory and the Center for Gravitational Waves and Cosmology at West Virginia University. All of the UCLA students participated in the 2016 course, “Search for Extraterrestrial Intelligence: Theory and Applications“.

Together, the team selected 14 systems from the Kepler catalog and examined them for technosignatures. While radio waves are a common occurrence in the cosmos, not all sources can be easily attributed to natural causes. Where and when this is the case, scientists conduct additional studies to try and rule out the possibility that they are a technosignature. As Professor Margot told Universe Today via email:

“In our article, we define a “technosignature” as any measurable property or effect that provides scientific evidence of past or present technology, by analogy with “biosignatures,” which provide evidence of past or present life.”

For the sake of their study, the team conducted an L-band radio survey of these 14 planetary systems. Specifically, they looked for signs of radio waves in the 1.15 to 1.73 gigahertz (GHz) range. At those frequencies, their study is sensitive to Arecibo-class transmitters located within 450 light-years of Earth. So if any of these systems have civilizations capable of building radio observatories comparable to Arecibo, the team hoped to find out!

Spring 2016 UCLA SETI class with Larry Lesyna. Credit: UCLA

“We searched for signals that are narrow (< 10 Hz) in the frequency domain,” said Margot. “Such signals are technosignatures because natural sources do not emit such narrowband signals… We identified approximately 850,000 candidate signals, of which 19 were of particular interest. Ultimately, none of these signals were attributable to an extraterrestrial source.”

What they found was that of the 850,000 candidate signals, about 99% of them were automatically ruled out because they were quickly determined to be the result of human-generated radio-frequency interference (RFI). Of the remaining candidates, another 99% were also flagged as anthropogenic because their frequencies overlapped with other known sources of RFI – such as GPS systems, satellites, etc.

The 19 candidate signals that remained were heavily scrutinized, but none could be attributed to an extraterrestrial source. This is key when attempting to distinguish potential signs of intelligence from radio signals that come from the only intelligence we know of (i.e. us!) Hence why astronomers have historically been intrigued by strong narrowband signals (like the WOW! Signal, detected in 1977) and the Lorimer Burst detected in 2007.

In these cases, the sources appeared to be coming from the Messier 55 globular cluster and the Large Magellanic Cloud, respectively. The latter was especially fascinating since it was the first time that astronomers had observered what are now known as Fast Radio Bursts (FRBs). Such bursts, especially when they are repeating in nature, are considered to be one of the best candidates in the search for intelligent, technologically-advanced life.

The UCLA SETI Group banner, featuring a photo of the central region of the Milky Way Galaxy. Credit: Yuri Beletsky/Carnegie Las Campanas Observatory

Unfortunately, these sources are still being investigated and scientists cannot attribute them to unnatural causes just yet. And as Professor Margot indicated, this study (which covered only 14 of the many thousand exoplanets discovered by Kepler) is just the tip of the iceberg:

“Our study encompassed only a small fraction of the search volume.  For instance, we covered less than five-millionths of the entire sky.  We are eager to scale the effort to sample a larger fraction of the search volume. We are currently seeking funds to expand our search.”

Between Kepler‘s first and second mission (K2), a total of 5,118 candidates and 2,538 confirmed exoplanets have been discovered within our galaxy alone. As of February 1st, 2018, a grand total of 3,728 exoplanets have been confirmed in 2,794 systems, with 622 systems having more than one planet. On top of that, a team of researchers from the University of Oklahoma recently made the first detection of extra-galactic planets as well!

It would therefore be no exaggeration to say that the hunt for ETI is still in its infancy, and our efforts are definitely beginning to pick up speed. There is literally a Universe of possibilities out there and to think that there are no other civilizations that are also looking for us seems downright unfathomable. To quote the late and great Carl Sagan: “The Universe is a pretty big place. If it’s just us, seems like an awful waste of space.”

And be sure to check out this video of the 2017 UCLA SETI Group, courtesy of the UCLA EPSS department:

Further Reading: arXiv

Posted on by Matt Williams

Using Atmospheric Beacons to Search for Signs of Extra-Terrestrial Life

This illustration shows a star's light illuminating the atmosphere of a planet. Credits: NASA Goddard Space Flight Center

Despite the thousands of exoplanets that have been discovered by astronomers in recent years, determining whether or not any of them are habitable is a major challenge. Since we cannot study these planets directly, scientists are forced to look for indirect indications. These are known as biosignatures, which consist of the chemical byproducts we associate with organic life showing up in a planet’s atmosphere.

A new study by a team of NASA scientists proposes a new method to search for potential signs of life beyond our Solar System. The key, they recommend, is to takes advantage of frequent stellar storms from cool, young dwarf stars. These storms hurl huge clouds of stellar material and radiation into space, interacting with exoplanet atmospheres and producing biosignatures that could be detected.

The study, titled “Atmospheric Beacons of Life from Exoplanets Around G and K Stars“, recently appeared in Nature Scientific Reports. Led by Vladimir S. Airapetian, a senior astrophysicist with the Heliophysics Science Division (HSD) at the NASA Goddard Space Flight Center, the team included members from NASA’s Langley Research Center, the Science Systems and Applications Incorporated (SSAI), and the American University.

Beacons of life could help researchers identify potentially habitable worlds. Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk

Traditionally, researchers have searched for signs of oxygen and methane in exoplanet atmospheres, since these are well-known byproducts of organic processes. Over time, these gases accumulate, reaching amounts that could be detected using spectroscopy. However, this approach is time-consuming and requires that astronomers spend days trying to observe spectra from a distant planet.

But according to Airapetian and his colleagues, it is possible to search for cruder signatures on potentially habitable worlds. This approach would rely on existing technology and resources and would take considerably less time. As Airapetian explained in a NASA press release:

“We’re in search of molecules formed from fundamental prerequisites to life — specifically molecular nitrogen, which is 78 percent of our atmosphere. These are basic molecules that are biologically friendly and have strong infrared emitting power, increasing our chance of detecting them.”

Using life on Earth as a template, Airapetian and his team designed a new method to look or signs of water vapor, nitrogen and oxygen gas byproducts in exoplanets atmospheres. The real trick, however, is to take advantage of the kinds of extreme space weather events that occur with active dwarf stars. These events, which expose planetary atmospheres to bursts of radiation, cause chemical reactions that astronomers can pick on.

Artist’s impression of the cool red star above a distant exoplanet. Credit: University of Warwick/Mark Garlick.

When it comes to stars like our Sun, a G-type yellow dwarf, such weather events are common when they are still young. However, other yellow and orange stars are known to remain active for billions of years, producing storms of energetic, charged particles. And M-type (red dwarf) stars, the most common type in the Universe, remain active throughout their long-lives, periodically subjecting their planets to mini-flares.

When these reach an exoplanet, they react with the atmosphere and cause the chemical dissociation of nitrogen (N²) and oxygen (O²) gas into single atoms, and water vapor into hydrogen and oxygen. The broken down nitrogen and oxygen atoms then cause a cascade of chemical reactions which produce hydroxyl (OH), more molecular oxygen (O), and nitric oxide (NO) – what scientists refer to as “atmospheric beacons”.

When starlight hits a planet’s atmosphere, these beacon molecules absorb the energy and emit infrared radiation. By examining the particular wavelengths of this radiation, scientists are able to determine what chemical elements are present. The signal strength of these elements is also an indication of atmospheric pressure. Taken together, these readings allow scientist’s to determine an atmosphere’s density and composition.

For decades, astronomers have also used a model to calculate how ozone (O³) is formed in Earth’s atmosphere from oxygen that is exposed to solar radiation. Using this same model – and pairing it with space weather events that are expected from cool, active stars – Airapetian and his colleagues sought to calculate just how much nitric oxide and hydroxyl would form in an Earth-like atmosphere and how much ozone would be destroyed.

Artist’s concept of NASA’s TIMED spacecraft, which has been observing Earth’s upper atmosphere for 15 years. Credits: NASA/JHU-APL

To accomplish this, they consulted data from NASA’s Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) mission, which has been studying the formation of beacons in Earth’s atmosphere for years. Specifically, they used data from its Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, which allowed them to simulate how infrared observations of these beacons might appear in exoplanet atmospheres.

As Martin Mlynczak, the SABER associate principal investigator at NASA’s Langley Research Center and a co-author of the paper, indicated:

“Taking what we know about infrared radiation emitted by Earth’s atmosphere, the idea is to look at exoplanets and see what sort of signals we can detect. If we find exoplanet signals in nearly the same proportion as Earth’s, we could say that planet is a good candidate for hosting life.”

What they found was that the frequency of intense stellar storms was directly related to the strength of the heat signals coming from the atmospheric beacons. The more storms occur, the more beacon molecules are created, generating a signal strong enough to be observed from Earth with a space telescope, and based on just two hours of observation time.

An exoplanet seen from its moon (artist's impression). Via the IAU.
An exoplanet seen from its moon (artist’s impression). Credit: IAU

They also found that this kind of method can weed out exoplanets that do not possess an Earth-like magnetic field, which naturally interact with charged particles from the Sun. The presence of such a field is what ensures that a planet’s atmosphere is not stripped away, and is therefore essential to habitability. As Airapetian explained:

“A planet needs a magnetic field, which shields the atmosphere and protects the planet from stellar storms and radiation. If stellar winds aren’t so extreme as to compress an exoplanet’s magnetic field close to its surface, the magnetic field prevents atmospheric escape, so there are more particles in the atmosphere and a stronger resulting infrared signal.”

This new model is significant for several reasons. On the one hand, it shows how research that has enabled detailed studies of Earth’s atmosphere and how it interacts with space weather is now being put towards the study of exoplanets. It is also exciting because it could allow for new studies of exoplanet habitability around certain classes of stars – ranging from many types of yellow and orange stars to cool, red dwarf stars.

Red dwarfs are the most common type of star in the Universe, accounting for 70% of stars in spiral galaxies and 90% in elliptical galaxies. What’s more, based on recent discoveries, astronomers estimate that red dwarf stars are very likely to have systems of rocky planets. The research team also anticipates that next-generation space instruments like the James Webb Space Telescope will increase the likelihood of finding habitable planets using this model.

This artist’s impression shows the planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Credit: ESO

As William Danchi, a Goddard senior astrophysicist and co-author on the study, said:

“New insights on the potential for life on exoplanets depend critically on interdisciplinary research in which data, models and techniques are utilized from NASA Goddard’s four science divisions: heliophysics, astrophysics, planetary and Earth sciences. This mixture produces unique and powerful new pathways for exoplanet research.”

Until such time that we are able to study exoplanets directly, any development that makes biosignatures more discernible and easier to detect is incredibly valuable. In the coming years, Project Blue and Breakthrough Starshot are hoping to conduct the first direct studies of the Alpha Centauri system. But in the meantime, improved models that allow us to survey countless other stars for potentially habitable exoplanets are golden!

Not only will they vastly improve our understanding of just how common such planets are, they might just point us in the direction of one or more Earth 2.0s!

Further Reading: NASA, Nature Scientific Reports

Posted on by Matt Williams

Metal-Eating Bacteria Could Have Left their “Fingerprints” on Mars, Proving it Once Hosted Life

Future missions could determine the presence of past life on Mars by looking for signs of extreme metal-metabolizing bacteria. Credit: NASA.

Today, there are multiple lines of evidence that indicate that during the Noachian period (ca. 4.1 to 3.7 billion years ago), microorganisms could have existed on the surface of Mars. These include evidence of past water flows, rivers and lakebeds, as well as atmospheric models that indicate that Mars once had a denser atmosphere. All of this adds up to Mars having once been a warmer and wetter place than it is today.

However, to date, no evidence has been found that life ever existed on Mars. As a result, scientists have been trying to determine how and where they should look for signs of past life. According to a new study by a team of European researchers, extreme lifeforms that are capable of metabolizing metals could have existed on Mars in the past. The “fingerprints” of their existence could be found by looking at samples of Mars’ red sands.

For the sake of their study, which recently appeared in the scientific journal Frontiers of Microbiology, the team created a “Mars Farm” to see how a form of extreme bacteria might fare in an ancient Martian environment. This environment was characterized by a comparatively thin atmosphere composed of mainly of carbon dioxide, as well as simulated samples of Martian regolith.

Metallosphaera sedula grown on synthetic Martian Regolith. The microbes are specifically stained by Fluorescence-In-Situ-Hybridization (FISH). Credit: Tetyana Milojevic

They then introduced a strain of bacteria known as Metallosphaera sedula, which thrives in hot, acidic environments. In fact, the bacteria’s optimal conditions are those where temperatures reach 347.1 K (74 °C; 165 °F)  and pH levels are 2.0 (between lemon juice and vinegar). Such bacteria are classified as chemolithotrophs, which means that they are able to metabolize inogranic metals – like iron, sulfur and even uranium.

These stains of bacteria were then added to the samples of regolith that were designed to mimic conditions in different locations and historical periods on Mars. First, there was sample MRS07/22, which consisted of a highly-porous type of rock that is rich in silicates and iron compounds. This sample simulated the kinds of sediments found on the surface of Mars.

Then there was P-MRS, a sample that was rich in hydrated minerals, and the sulfate-rich S-MRS sample, which mimic Martian regolith that was created under acidic conditions. Lastly, there was the sample of JSC 1A, which was largely composed of the volcanic rock known as palagonite. With these samples, the team was able to see exactly how the presence of extreme bacteria would leave biosignatures that could be found today.

As Tetyana Milojevic – an Elise Richter Fellow with the Extremophiles Group at the University of Vienna and a co-author on the paper – explained in a University of Vienna press release:

“We were able to show that due to its metal oxidizing metabolic activity, when given an access to these Martian regolith simulants, M. sedula actively colonizes them, releases soluble metal ions into the leachate solution and alters their mineral surface leaving behind specific signatures of life, a ‘fingerprint’, so to say.”

Microspheroids containing mostly aluminium and chlorine overgrow the mineral surface of synthetic Mars regolith. These microspheroids can only be observed after cultivation of Metallosphaera sedula Credit: Tetyana Milojevic

The team then examined the samples of regolith to see if they had undergone any bioprocessing, which was possible thanks to the assistance of Veronika Somoza – a chemist from the University of Vienna’s Department of Physiological Chemistry and a co-author on the study. Using an electron microscope, combined with analytical spectroscopy technique, the team sought to determine if metals with the samples had been consumed.

In the end, the sets of microbiological and mineralogical data they obtained showed signs of free soluble metals, which indicated that the bacteria had effectively colonized the regolith samples and metabolized some of the metallic minerals within. As Milojevic indicated:

“The obtained results expand our knowledge of biogeochemical processes of possible life beyond Earth, and provide specific indications for detection of biosignatures on extraterrestrial material – a step further to prove potential extra-terrestrial life.”

In effect, this means that extreme bacteria could have existed on Mars billions of years ago. And thanks to the state of Mars today – with its thin atmosphere and lack of precipitation – the biosignatures they left behind (i.e. traces of free soluble metals) could be preserved within Martian regolith. These biosignatures could therefore be detected by upcoming sample-return missions, such as the Mars 2020 rover.

Biotransformed synthetic Martian Regolith after Metallosphaera sedula cultivation. Credit: Tetyana Milojevic

In addition to pointing the way towards possible indications of past life on Mars, this study is also significant as far as the hunt for life on other planets and star systems is concerned. In the future, when we are able to study extra-solar planets directly, scientists will likely be looking for signs of biominerals. Among other things, these “fingerprints” would be a powerful indicator of the existence of extra-terrestrial life (past or present).

Studies of extreme lifeforms and the role they play in the geological history of Mars and other planets is also helpful in advancing our understanding of how life emerged in the early Solar System. On Earth too, extreme bacteria played an important role in turning the primordial Earth into a habitable environment, and play an important role in geological processes today.

Last, but not least, studies of this nature could also pave the way for biomining, a technique where strains of bacteria extract metals from ores. Such a process could be used for the sake of space exploration and resource exploitation, where colonies of bacteria are sent out to mine asteroids, meteors and other celestial bodies.

Further Reading: University of Vienna, Frontiers in Microbiology