Artist's conception of a terraformed Mars. Credit: Ittiz/Wikimedia Commons
Billions of years ago, Earth’s atmosphere was much different than it is today. Whereas our current atmosphere is a delicate balance of nitrogen gas, oxygen and trace gases, the primordial atmosphere was the result of volcanic outgassing – composed primarily of carbon dioxide, methane, ammonia, and other harsh chemicals. In this respect, our planet’s ancient atmosphere has something in common with Mars’ current atmosphere.
For this reason, some researchers think that introducing photosynthetic bacteria, which helped covert Earth’s atmosphere to what it is today, could be used to terraform Mars someday. According to a new study by an international team of scientists, it appears that cyanobacteria can conduct photosynthesis in low-light conditions. The results of this study could have drastic implications for Mars, where low-light conditions are common.
Cyanobacteria are some of the most ancient organisms on Earth, with fossil evidence indicating that they existed as early as the Archean Era (c.a 3.5 billion years ago). During this time, they played a vital role in converting the abundant CO² in the atmosphere into oxygen gas, which eventually gave rise to ozone (O³) that helped protect the planet from harmful solar radiation.
The photochemistry used by these microbes is similar to what plants and trees – which subsequently evolved – rely on today. The process comes down to red light, which plants absorb, while reflecting green lights thanks to their chlorophyll content. The darker the environment, the less energy plants are able to adsorb, and thus convert into chemical energy.
For the sake of their study, the team led by Nürnberg sought to investigate just how dark an environment can become before photosynthesis becomes impossible. Using a species of bacteria known as Chroococcidiopsis thermalis (C. thermalis), they exposed samples of cyanobacteria to low light to find out what the lowest wavelengths that they could absorb were.
Previous research has suggested that the lower limit for photochemistry to occur was a light wavelength of 700 nanometers – known as the “red limit”. However, the team found that C. thermalis continued to conduct photosynthesis at wavelengths of up to 750 nanometers. The key, according to the team, lies in the presence of previously undetected long-wavelength chlorophylls, which the researchers traced back to the C. thermalis genome.
The researchers traced the origin of these chlorophylls to the C. thermalis genome, which they located in a specific gene cluster that is common in many species of cyanobacteria. This suggests that the ability to surpass the red limit is actually quite common, which has numerous implications. For one, the findings indicate that the limits of photosynthesis are greater than previously thought.
On the other hand, these findings indicate that certain organisms can function using less fuel, which the researchers refer to as an “unprecedented low-energy photosystem”. To Krausz and his colleagues, this photosystem could be the first wave in an effort to terraform Mars. Along with efforts to thicken the atmosphere and warm the environment, the introduction of C. thermalis and terrestrial plants could slowly make Mars suitable for human habitation.
“This might sound like science fiction, but space agencies and private companies around the world are actively trying to turn this aspiration into reality in the not-too-distant future. Photosynthesis could theoretically be harnessed with these types of organisms to create air for humans to breathe on Mars. Low-light adapted organisms, such as the cyanobacteria we’ve been studying, can grow under rocks and potentially survive the harsh conditions on the red planet.”
Artist’s concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One
In this respect, Krausz and his colleagues are joined by groups like the CyanoKnights – a team of students and volunteer scientists from the University of Applied Science and the Technical University in Darmstadt, Germany. Much like Krausz’s team, the CyanoKnights that want to seed Mars with cyanobacteria in order to trigger an ecological transformation, thus paving the way for colonization.
This idea was submitted as part of the Mars One University Competition, which took place in the summer of 2014. What’s more, there have been recent research findings that indicate that organisms similar to cyanobacteria may already exist on other planets. If this most recent study is correct, it means that such organisms could survive in low-light conditions, which means astronomers could expand their search for potential life to other locations in the Universe.
From offering humans the means to conduct terraforming under more restrictive conditions to assisting in the search for extra-terrestrial life, this research could have some drastic implications for our understanding of life in the Universe, and how to expand our place in it.
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A view of Ceres in natural colour, pictured by the Dawn spacecraft in May 2015. Credit: NASA/ JPL/Planetary Society/Justin Cowart
In March of 2015, NASA’s Dawn mission became the first spacecraft to visit the protoplanet Ceres, the largest body in the Main Asteroid Belt. It was also the first spacecraft to visit a dwarf planet, having arrived a few months before the New Horizons mission made its historic flyby of Pluto. Since that time, Dawn has revealed much about Ceres, which in turn is helping scientists to understand the early history of the Solar System.
Last year, scientists with NASA’s Dawn mission made a startling discovery when they detected complex chains of carbon molecules – organic material essential for life – in patches on the surface of Ceres. And now, thanks to a new study conducted by a team of researchers from Brown University (with the support of NASA), it appears that these patches contain more organic material than previously thought.
The new findings were recently published in the scientific journal Geophysical Research Letters under the title “New Constraints on the Abundance and Composition of Organic Matter on Ceres“. The study was led by Hannah Kaplan, a postdoctoral researcher at Brown University, with the assistance of Ralph E. Milliken and Conel M. O’D. Alexander – an assistant professor at Brown University and a researcher from the Carnegie Institution of Washington, respectively.
A new analysis of Dawn mission data suggests those organics could be more plentiful than originally thought. Credit: NASA/Rendering by Hannah Kaplan
The organic materials in question are known as “aliphatics”, a type of compound where carbon atoms form open chains that are commonly bound with oxygen, nitrogen, sulfur and chlorine. To be fair, the presence of organic material on Ceres does not mean that the body supports life since such molecules can arise from non-biological processes.
Aliphatics have also been detected on other planets in the form of methane (on Mars and especially on Saturn’s largest moon, Titan). Nevertheless, such molecules remains an essential building block for life and their presence at Ceres raises the question of how they got there. As such, scientists are interested in how it and other life-essential elements (like water) has been distributed throughout the Solar System.
Since Ceres is abundant in both organic molecules and water, it raises some intriguing possibilities about the protoplanet. The results of this study and the methods they used could also provide a template for interpreting data for future missions. As Dr. Kaplan – who led the research while completing her PhD at Brown – explained in a recent Brown University press release:
“What this paper shows is that you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data. That’s important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material.”
Enhanced color-composite image, made with data from the framing camera aboard NASA’s Dawn spacecraft, shows the area around Ernutet crater. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The original discovery of organics on Ceres took place in 2017 when an international team of scientists analyzed data from the Dawn mission’s Visible and Infrared Mapping Spectrometer (VIRMS). The data provided by this instrument indicated the presence of these hydrocarbons in a 1000 km² region around of the Ernutet crater, which is located in the northern hemisphere of Ceres and measures about 52 km (32 mi) in diameter.
To get an idea of how abundant the organic compounds were, the original research team compared the VIRMS data to spectra obtained in a laboratory from Earth rocks with traces of organic material. From this, they concluded that between 6 and 10% of the spectral signature detected on Ceres could be explained by organic matter.
They also hypothesized that the molecules were endogenous in origin, meaning that they originated from inside the protoplanet. This was consistent with previous surveys that showed signs of hydorthermal activity on Ceres, as well others that have detected ammonia-bearing hydrated minerals, water ice, carbonates, and salts – all of which suggested that Ceres had an interior environment that can support prebiotic chemistry.
But for the sake of their study, Kaplan and her colleagues re-examined the data using a different standard. Instead of relying on Earth rocks for comparison, they decided to examine an extraterrestrial source. In the past, some meteorites – such as carbonaceous chondrites – have been shown to contain organic material that is slightly different than what we are familiar with here on Earth.
Artist’s rendition of the Dawn mission on approach to the protoplanet Ceres. Credit: NASA/JPL
After re-examining the spectral data using this standard, Kaplan and her team determined that the organics found on Ceres were distinct from their terrestrial counterparts. As Kaplan explained:
“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there. We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”
If the concentrations of organic material are indeed that high, then it raises new questions about where it came from. Whereas the original discovery team claimed it was endogenous in origin, this new study suggests that it was likely delivered by an organic-rich comet or asteroid. On the one hand, the high concentrations on the surface of Ceres are more consistent with a comet impact.
This is due to the fact that comets are known to have significantly higher internal abundances of organics compared with primitive asteroids, similar to the 40% to 50% figure this study suggests for these locations on Ceres. However, much of those organics would have been destroyed due to the heat of the impact, which leaves the question of how they got there something of a mystery.
Dawn spacecraft data show a region around the Ernutet crater where organic concentrations have been discovered (labeled “a” through “f”). The color coding shows the strength of the organics absorption band, with warmer colors indicating the highest concentrations. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF/MPS/DLR/IDA
If they did arise endogenously, then there is the question of how such high concentrations emerged in the northern hemisphere. As Ralph Milliken explained:
“If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots. It’s not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples.”
Given that the Main Asteroid Belt is composed of material left over from the formation of the Solar System, determining where these organics came from is expected to shed light on how organic molecules were distributed throughout the Solar System early in its history. In the meantime, the researchers hope that this study will inform upcoming sample missions to near-Earth asteroids (NEAs), which are also thought to host water-bearing minerals and organic compounds.
These include the Japanese spacecraft Hayabusa2, which is expected to arrive at the asteroid Ryugu in several weeks’ time, and NASA’s OSIRIS-REx mission – which is due to reach the asteroid Bennu in August. Dr. Kaplan is currently a science team member with the OSIRIS-REx mission and hopes that the Dawn study she led will help the OSIRIS-REx‘s mission characterize Bennu’s environment.
“I think the work that went into this study, which included new laboratory measurements of important components of primitive meteorites, can provide a framework of how to better interpret data of asteroids and make links between spacecraft observations and samples in our meteorite collection,” she said. “As a new member to the OSIRIS-REx team, I’m particularly interested in how this might apply to our mission.”
The New Horizons mission is also expected to rendezvous with the Kuiper Belt Object (KBO) 2014 MU69 on January 1st, 2019. Between these and other studies of “ancient objects” in our Solar System – not to mention interstellar asteroids that are being detected for the first time – the history of the Solar System (and the emergence of life itself) is slowly becoming more clear.
HiRISE image from NASA's Mars Reconnaissance Orbiter (MRO) showing an impact crater that triggered a slope streak. Credit: NASA/JPL/University of Arizona
In 2006, NASA’s Mars Reconnaissance Orbiter (MRO) established orbit around the Red Planet. Using an advanced suite of scientific instruments – which include cameras, spectrometers, and radar – this spacecraft has been analyzing landforms, geology, minerals and ice on Mars for years and assisting with other missions. While the mission was only meant to last two years, the orbiter has remained in operation for the past twelve.
In that time, the MRO has acted as a relay for other missions to send information back to Earth and provided a wealth of information of its own on the Red Planet. Most recently, it captured an image of an impact crater that caused a landslide, which left a long, dark streak along the crater wall. Such streaks are created when dry dust collapses down the edge of a Martian hill, leaving behind dark swaths.
Close up of the crater captured by the MRO’s HiRISE instrument. Credit: NASA/JPL/University of Arizona
In this respect, these avalanches are not unlike Recurring Slope Lineae (RSL), where seasonal dark streaks appear along slopes during warmer days on Mars. These are believed to be caused by either salt water flows or dry dust grains falling naturally. In this case, however, the dry dust on the slope was destabilized by the meteor’s impact, which exposed darker material beneath.
The impact that created the crater is believed to have happened about ten years ago. And while the crater itself (shown above) is only 5 meters (16.4 feet) across, the streak it resulted in is 1 kilometer (0.62 mi) long! The image also captured the faded scar of an old avalanche, which is visible to the side of the new dark streak.
Wider-angle view of the impact crater captured by the MRO’s HiRISE instrument and the resulting dark streak. Credit: NASA/JPL/University of Arizona
This is just the latest in a long-line of images and data packages sent back by the MRO. By providing daily reports on Mars’ weather and surface conditions, and studying potential landing sites, the MRO also paves the way for future spacecraft and surface missions. In the future, the orbiter will serve as a highly capable relay satellite for missions like NASA’s Mars 2020 rover, which will continue in the hunt for signs of past life on Mars.
At present, the MRO has enough propellant to keep functioning into the 2030s, and given its intrinsic value to the study of Mars, it is likely to remain in operation right up until it exhausts its fuel. Perhaps it will even be working when astronauts arrived on the Red Planet?
Artist's impression of the "Black Hole Ultimate Solar System". Credit: planetplanet.net
Shortly after Einstein published his Theory of General Relativity in 1915, physicists began to speculate about the existence of black holes. These regions of space-time from which nothing (not even light) can escape are what naturally occur at the end of most massive stars’ life cycle. While black holes are generally thought to be voracious eaters, some physicists have wondered if they could also support planetary systems of their own.
Looking to address this question, Dr. Sean Raymond – an American physicist currently at the University of Bourdeaux – created a hypothetical planetary system where a black hole lies at the center. Based on a series of gravitational calculations, he determined that a black hole would be capable of keeping nine individual Suns in a stable orbit around it, which would be able to support 550 planets within a habitable zone.
He named this hypothetical system “The Black Hole Ultimate Solar System“, which consists of a non-spinning black hole that is 1 million times as massive as the Sun. That is roughly one-quarter the mass of Sagittarius A*, the super-massive black hole (SMBH) that resides at the center of the Milky Way Galaxy (which contains 4.31 million Solar Masses).
Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.
As Raymond indicates, one of the immediate advantages of having this black hole at the center of a system is that it can support a large number of Suns. For the sake of his system, Raymond chose 9, thought he indicates that many more could be sustained thanks to the sheer gravitational influence of the central black hole. As he wrote on his website:
“Given how massive the black hole is, one ring could hold up to 75 Suns! But that would move the habitable zone outward pretty far and I don’t want the system to get too spread out. So I’ll use 9 Suns in the ring, which moves everything out by a factor of 3. Let’s put the ring at 0.5 AU, well outside the innermost stable circular orbit (at about 0.02 AU) but well inside the habitable zone (from about 2.7 to 5.4 AU).”
Another major advantage of having a black hole at the center of a system is that it shrinks what is known as the “Hill radius” (aka. Hill sphere, or Roche sphere). This is essentially the region around a planet where its gravity is dominant over that of the star it orbits, and can therefore attract satellites. According to Raymond, a planet’s Hill radius would be 100 times smaller around a million-sun black hole than around the Sun.
This means that a given region of space could stably fit 100 times more planets if they orbited a black hole instead of the Sun. As he explained:
“Planets can be super close to each other because the black hole’s gravity is so strong! If planets are little toy Hot wheels cars, most planetary systems are laid out like normal highways (side note: I love Hot wheels). Each car stays in its own lane, but the cars are much much smaller than the distance between them. Around a black hole, planetary systems can be shrunk way down to Hot wheels-sized tracks. The Hot wheels cars — our planets — don’t change at all, but they can remain stable while being much closer together. They don’t touch (that would not be stable), they are just closer together.”
This is what allows for many planets to be placed with the system’s habitable zone. Based on the Earth’s Hill radius, Raymond estimates that about six Earth-mass planets could fit into stable orbits within the same zone around our Sun. This is based on the fact that Earth-mass planets could be spaced roughly 0.1 AU from each other and maintain a stable orbit.
Given that the Sun’s habitable zone corresponds roughly to the distances between Venus and Mars – which are 0.3 and 0.5 AU away, respectively – this means there is 0.8 AUs of room to work with. However, around a black hole with 1 million Solar Masses, the closest neighboring planet could be just 1/1000th (0.001) of an AU away and still have a stable orbit.
Doing the math, this means that roughly 550 Earths could fit in the same region orbiting the black hole and its nine Suns. There is one minor drawback to this whole scenario, which is that the black hole would have to remain at its current mass. If it were to become any larger, it would cause the Hill radii of its 550 planets to shrink down further and further.
Once the Hill radius got down to the point where it was the same size as any of the Earth-mass planets, the black hole would begin to tear them apart. But at 1 million Solar masses, the black hole is capable of supporting a massive system of planets comfortably. “With our million-Sun black hole the Earth’s Hill radius (on its current orbit) would already be down to the limit, just a bit more than twice Earth’s actual radius,” he says.
Illustration of tightly-packed orbits of Earth-mass planets in orbit around the Sun (in black) vs. around a supermassive black hole (green). Credit: Sean Raymond
Lastly, Raymond considers the implications that living in such a system would have. For one, a year on any planet within the system’s habitable zone would be much shorter, owing to the fact their orbital periods would be much faster. Basically, a year would last roughly 1.6 days for planets at the inner edge of the habitable zone and 4.6 days for planets at the outer edge of the habitable zone.
In addition, on the surface of any planet in the system, the sky would be a lot more crowded! With so many planets in close orbit together, they would pass very close to one another. That essentially means that from the surface of any individual Earth, people would be able to see nearby Earths as clear as we see the Moon on some days. As Raymond illustrated:
“At closest approach (conjunction) the distance between planets is about twice the Earth-Moon distance. These planets are all Earth-sized, about 4 times larger than the Moon. This means that at conjunction each planet’s closest neighbor appears about twice the size of the full Moon in the sky. And there are two nearest neighbors, the inner and outer one. Plus, the next-nearest neighbors are twice as far away so they are still as big as the full Moon during conjunction. And four more planets that would be at least half the full Moon in size during conjunction.”
He also indicates that conjunctions would occur almost once per orbit, which would mean that every few days, there would be no shortage of giant objects passing across the sky. And of course, there would be the Sun’s themselves. Recall that scene in Star Wars where a young Luke Skywalker is watching two suns set in the desert? Well, it would a little like that, except way more cool!
According to Raymond’s calculations, the nine Suns would complete an orbit around the black hole every three hours. Every twenty minutes, one of these Suns would pass behind the black hole, taking just 49 seconds to do so. At this point, gravitational lensing would occur, where the black hole would focus the Sun’s light toward the planet and distort the apparent shape of the Sun.
To illustrate what this would look like, he provides an animation (shown above) created by @GregroxMun – a planet modeller who develops space graphics for Kerbal and other programs – using Space Engine.
While such a system may never occur in nature, it is interesting to know that such a system would be physically possible. And who knows? Perhaps a sufficiently advanced species, with the ability to tow stars and planets from one system and place them in orbit around a black hole, could fashion this Ultimate Solar System. Something for SETI researchers to be on the lookout for, perhaps?
This hypothetical exercise was the second installment in two-part series by Raymond, titled “Black holes and planets”. In the first installment, “The Black Hole Solar System“, Raymond considered what it would be like if our system orbited around a black hole-Sun binary. As he indicated, the consequences for Earth and the other Solar planets would be interesting, to say the least!
A concept for a multi-generation ship being designed by the TU Delft Starship Team (DSTART), with support from the ESA. Credit and Copyright: Nils Faber & Angelo Vermeulen
Humanity has long dreamed about sending humans to other planets, even before crewed spaceflight became a reality. And with the discovery of thousands of exoplanets in recent decades, particularly those that orbit within neighboring star systems (like Proxima b), that dream seems closer than ever to becoming a reality. But of course, a lot of technical challenges need to be overcome before we can hope to mount such a mission.
In addition, a lot of questions need to be answered. For example, what kind of ship should we send to Proxima b or other nearby exoplanets? And how many people would we need to place aboard that ship? The latter question was the subject of a recent paper written by a team of French researchers who calculated the minimal number of people that would be needed in order to ensure that a healthy multi-generational crew could make the journey to Proxima b.
Artistic representations of a Clarke exobelt with a portrait of Sir Arthur C. Clarke in the background. Credit: Caro Waro (@carwaro).
When it comes to the search for extra-terrestrial intelligence (SETI) in the Universe, there is the complicated matter of what to be on the lookout for. Beyond the age-old question of whether or not intelligent life exists elsewhere in the Universe (statistically speaking, it is very likely that it does), there’s also the question of whether or not we would be able to recognize it if and when we saw it.
Given that humanity is only familiar with one form of civilization (our own), we tend to look for indications of technologies we know or which seem feasible. In a recent study, a researcher from the Instituto de Astrofísica de Canarias (IAC) proposed looking for large bands of satellites in distant star systems – a concept that was proposed by the late and great Arthur C. Clarke (known as a Clarke Belt).
The study – titled “Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt” – was conducted by Hector Socas-Navarro, an astrophysicist with the IAC and the Universidad de La Laguna. In it, he advocates using next-generation telescopes to look for signs of massive belts of geostationary communication satellites in distant star systems.
This proposal is based in part on a paper written by Arthur C. Clarke in 1945 (titled “Peacetime Uses for V2“), in which he proposed sending “artificial satellites” into geostationary orbit around Earth to create a global communications network. At present, there are about 400 such satellites in the “Clarke Belt” – a region named in honor of him that is located 36,000 km above the Earth.
This network forms the backbone of modern telecommunications and in the future, many more satellites are expected to be deployed – which will form the backbone of the global internet. Given the practicality of satellites and the fact that humanity has come to rely on them so much, Socas-Navarro considers that a belt of artificial satellites could naturally be considered “technomarkers” (the analogues of “biomarkers”, which indicate the presence of life).
As Socas-Navarro explained to Universe Today via email:
“Essentially, a technomarker is anything that we could potentially observe which would reveal the presence of technology elsewhere in the Universe. It’s the ultimate clue to find intelligent life out there. Unfortunately, interstellar distances are so great that, with our current technology, we can only hope to detect very large objects or structures, something comparable to the size of a planet.”
In this respect, a Clarke Exobelt is not dissimilar from a Dyson Sphere or other forms of megastructures that have been proposed by scientists in the past. But unlike these theoretical structures, a Clarke Exobelt is entirely feasible using present-day technology.
Graphic showing the cloud of space debris that currently surrounds the Earth. Credit: NASA’s Goddard Space Flight Center/JSC
“Other existing technomarkers are based on science fiction technology of which we know very little,” said Socas-Navarro. “We don’t know if such technologies are possible or if other alien species might be using them. The Clarke Exobelt, on the other hand, is a technomarker based on real, currently existing technology. We know we can make satellites and, if we make them, it’s reasonable to assume that other civilizations will make them too.”
According to Socas-Navarro, there is some “science fiction” when it comes to Clarke Exobelts that would actually be detectable using these instruments. As noted, humanity has about 400 operational satellites occupying Earth’s “Clarke Belt”. This is about one-third of the Earth’s existing satellites, whereas the rest are at an altitude of 2000 km (1200 mi) or less from the surface – the region known as Low Earth Orbit (LEO).
This essentially means that aliens would need to have billions more satellites within their Clarke Belt – accounting for roughly 0.01% of the belt area – in order for it to be detectable. As for humanity, we are not yet to the point where our own Belt would be detectable by an extra-terrestrial intelligence (ETI). However, this should not take long given that the number of satellites in orbit has been growing exponentially over the past 15 years.
Based on simulations conducted by Socas-Navarro, humanity will reach the threshold where its satellite band will be detectable by ETIs by 2200. Knowing that humanity will reach this threshold in the not-too-distant future makes the Clarke Belt a viable option for SETI. As Socas-Navarro explained:
“In this sense, the Clarke Exobelt is interesting because it’s the first technomarker that looks for currently existing technology. And it goes both ways too. Humanity’s Clarke Belt is probably too sparsely populated to be detectable from other stars right now (at least with technology like ours). But in the last decades we have been populating it at an exponential rate. If this trend were to continue, our Clarke Belt would be detectable from other stars by the year 2200. Do we want to be detectable? This is an interesting debate that humanity will have to resolve soon.
An exoplanet transiting across the face of its star, demonstrating one of the methods used to find planets beyond our solar system. Credit: ESA/C. Carreau
As for when we might be able to start looking for Exobelts, Socas-Navarro indicates that this will be possible within the next decade. Using instruments like the James Webb Space Telescope (JWST), the Giant Magellan Telescope (GMT), the European Extremely Large Telescope (E-ELT), and the Thirty Meter Telescope (TMT), scientists will have ground-based and space-based telescopes with the necessary resolution to spot these bands around exoplanets.
As for how these belts would be detected, that would come down to the most popular and effective means for finding exoplanets to date – the Transit Method (aka. Transit Photometry). For this method, astronomers monitor distant stars for periodic dips in brightness, which are indications of an exoplanet passing in front of the star. Using next-generation telescopes, astronomers may also be able to detect reflected light from a dense band of satellites in orbit.
“However, before we point our supertelescopes to a planet we need to identify good candidates,” said Socas-Navarro. “There are too many stars to check and we can’t go one by one. We need to rely on exoplanet search projects, such as the recently launched satellite TESS, to spot interesting candidates. Then we can do follow-up observations with supertelescopes to confirm or refute those candidates.”
In this respect, telescopes like the Kepler Space Telescope and the Transiting Exoplanet Survey Telescope (TESS) will still serve an important function in searching for technomarkers. Whereas the former telescope is due to retire soon, the latter is scheduled to launch in 2018.
Artist’s impression of an extra-solar planet transiting its star. Credit: QUB Astrophysics Research Center
While these space-telescopes would search for rocky planets that are located within the habitable zones of thousands of stars, next-generation telescopes could search for signs of Clarke Exobelts and other technomarkers that would be otherwise hard to spot. However, as Socas-Navarro indicated, astronomers could also find evidence of Exobands by sifting through existing data as well.
“In doing SETI, we have no idea what we are looking for because we don’t know what the aliens are doing,” he said. “So we have to investigate all the possibilities that we can think of. Looking for Clarke Exobelts is a new way of searching, it seems at least reasonably plausible and, most importantly, it’s free. We can look for signatures of Clarke Exobelts in currently existing missions that search for exoplanets, exorings or exomoons. We don’t need to build costly new telescopes or satellites. We simply need to keep our eyes open to see if we can spot the signatures presented in the simulation in the flow of data from all of those projects.”
Humanity has been actively searching for signs of extra-terrestrial intelligence for decades. To know that our technology and methods are becoming more refined, and that more sophisticated searches could begin within a decade, is certainly encouraging. Knowing that we won’t be visible to any ETIs that are out there for another two centuries, that’s also encouraging!
And be sure to check out this cool video by our friend, Jean Michael Godier, where he explains the concept of a Clarke Exobelt:
Artist's concept of the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) space telescope. Credits: NASA/GSFC
The Hubble Space Telescope has been in space for 28 years, producing some of the most beautiful and scientifically important images of the cosmos that humanity has ever taken. But let’s face it, Hubble is getting old, and it probably won’t be with us for too much longer.
NASA’s James Webb Space Telescope is in the final stages of testing, and WFIRST is waiting in the wings. You’ll be glad to know there are even more space telescopes in the works, a set of four powerful instruments in design right now, which will be part of the next Decadal Survey, and helping to answer the most fundamental questions about the cosmos.
The James Webb Space Telescope inside a cleanroom at NASA’s Johnson Space Center in Houston. Credit: NASA/JSC
I know, I know, the James Webb Space Telescope hasn’t even reached space yet, and there could still be more delays as it goes through its current round of tests. At the time I’m recording this video, it’s looking like May 2020, but come on, you know there’ll be delays.
And then there’s WFIRST, the wide angle infrared space telescope that’s actually made of an old Hubble class telescope that the National Reconnaissance Office didn’t need any more. The White House wants to cancel it, Congress saved it, and now NASA is getting parts of it constructed. Assuming it doesn’t run into more delays, we’re looking at a launch in the mid-2020s.
NASA’s Wide Field Infrared Survey Telescope (WFIRST) will capture Hubble-quality images covering swaths of sky 100 times larger than Hubble does. These enormous images will allow astronomers to study the evolution of the cosmos. Its Coronagraph Instrument will directly image exoplanets and study their atmospheres. Credits: NASA/GSFC/Conceptual Image Lab
I’ve actually done an episode about supertelescopes, and talked about James Webb and WFIRST, so if you want to learn more about those observatories, check that out first.
Today we’re going to go further into the future, to look at the next next generation telescopes. The ones that could be launched after the telescope that gets launched after the telescope that comes next.
Before I dig into these missions, I need to talk about the Decadal Survey. This is a report created by the US National Academy of Sciences for Congress and NASA. It’s essentially a wishlist from scientists to NASA, defining the biggest questions they have in their field of science.
This allows Congress to assign budgets and NASA to develop mission ideas that will help fulfill as many of these science goals as possible.
These surveys are done once every decade, bringing together committees in Earth science, planetary science, and astrophysics. They pitch ideas, argue, vote and eventually agree on a set of recommendations which will define science priorities over the next decade.
We’re currently in the 2013-2022 Decadal Survey period, so in just a few years, the next survey will be due, and define the missions from 2023-2032. I know, that really sounds like the distant future, but time’s actually running out to get the band back together.
We’re still a few years away from the final document, but serious proposals are in the planning stages for next generation space telescopes, and they are awesome. Let’s talk about them.
The first mission we’ll look at is HabEx, or the Habitable Exoplanet Imaging Mission. This is a spacecraft that will directly photograph planets orbiting other stars. It’ll be targeting all kinds of planets, from hot Jupiters to super Earths, but its primary target will be to photograph Earth-like exoplanets and measure their atmospheres.
Wavelengths of light that can help suggest biospheres. Credit: NASA/JPL
In other words, HabEx is going to try and detect signals of life in planets orbiting other stars.
In order to get this done, HabEx needs to block the light from the star, so that much fainter planets nearby can be revealed. It’ll have one and maybe two ways to do this.
The first is using a coronagraph. This is a tiny dot that sits inside the telescope itself, which is positioned in front of the star and blocks its light. The remaining light passing through the telescope comes from fainter objects around the star and can be imaged by the instrument’s sensor.
The telescope has a special deformable mirror that can be tweaked and tuned until the fainter planets come into view.
Here’s an example of a coronagraph in use, on the European Southern Observatory’s Very Large Telescope. The central star is hidden, revealing the dimmer dust disk around it. Here’s a direct image of a brown dwarf orbiting a star.
This infrared image shows the dust ring around the nearby star HR 4796A in the southern constellation of Centaurus. It was one of the first produced by the SPHERE instrument soon after it was installed on ESO’s Very Large Telescope in May 2014. It shows not only the ring itself with great clarity, but also reveals the power of SPHERE to reduce the glare from the very bright star — the key to finding and studying exoplanets in future.
And this is one of the most dramatic videos I think I’ve ever seen, with 4 Jupiter-sized worlds orbiting around the star HR 8799. It’s a bit of a trick, the researchers animated the motion of the planets in between observations, but still, wow.
The second method of blocking the light will be to use a Starshade. This is a completely separate spacecraft that looks like a pinwheel. It flies tens of thousands of kilometers away from the telescope, and when it’s positioned perfectly, it blocks the light from the central star, while allowing light from the planets to leak around the edges.
The trick with a Starshade is those petals, which create a softer edge so the light waves from the fainter planet is less bent. This creates a very dark shadow that should have the best chance at revealing planets.
Artist’s concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL
Unlike most missions, Starshades like this can be used with any observatory in space. So, Hubble, James Webb or any other observatory could take advantage of this instrument.
We’ve always complained about how we can only see a fraction of the planets out there using the transit or radial velocity method because of how things line up. But with a mission like HabEx, planets can be seen direction, in any configuration.
In addition to this primary mission, HabEx will also be used for a variety of astrophysics, like observing the early Universe, and studying the chemicals of the biggest stars before and after they explode as supernovae.
Next up, Lynx, which will be NASA’s next generation X-ray telescope. Surprisingly, it’s not an acronym, it’s just named after the animal. In various cultures Lynxes were thought to have the supernatural ability to see the true nature of things.
X-rays are at the higher end of the electromagnetic spectrum, and they’re blocked by the Earth’s atmosphere, so you need a space telescope to be able to see them. Right now, NASA has its Chandra X-ray Observatory, and ESA is working on its ATHENA mission, due for launch in 2028.
Lynx Mission Concept. Credit: NASA
Lynx will act as a partner to the James Webb Space Telescope, peering out to the edge of the observable Universe, revealing the first generations of supermassive black holes, and helping to chart their formation and mergers over time. It’ll see radiation coming from the hot gas from the early cosmic web, as the first galaxies were coming together.
And then it’ll be used to examine the kinds of objects Chandra, XMM Newton and other X-ray observatories focus on: pulsars, galaxy collisions, collapsars, supernovae, black holes, and more. Even normal stars can give off X-ray flares that tell us more about them.
The vast majority of the Universe’s matter is located in clouds of gas as hot as a million Kelvin. If you want to see the Universe as it truly is, you want to look at it in X-rays.
X-ray telescopes are different from visible light observatories like Hubble. You can’t just have a mirror that bounces X-rays. Instead, you use grazing-incidence mirrors which can slightly redirect photons that hit them, funneling them down to a detector.
Artist illustration of the Chandra X-ray Observatory. Chandra is the most sensitive X-ray telescope ever built. Credit: NASA/CXC/NGST
With a 3 meter outer mirror, the starting part of the funnel, it’ll provide 50-100 times the sensitivity with 16 times the field of view, gathering photons at 800 times the speed of Chandra.
I’m not sure what else to say. It’ll be a monster X-ray observatory. Trust me, astronomers think this is a very good idea.
Next, the Origins Space Telescope or OST. Like James Webb, and the Spitzer Space Telescope, OST is going to be an infrared telescope, designed to observe some of the coolest objects in the Universe. But it’s going to be even bigger. While James Webb has a primary mirror 6.5 meters across, the OST mirror will be 9.1 meters across.
Imagine a telescope almost as big as the largest ground telescopes on Earth, but out in space. In space.
Artist’s concept of the the Origins Space Telescope (OST). Credits: NASA/GSFC
It won’t just be big, it’ll be cold.
NASA was able to cool down Spitzer to just 5 Kelvin – that’s 5 degrees above absolute zero, and just a little warmer than the background temperature of the Universe. They’re planning to get Origins down to 4 Kelvin. It doesn’t sound like much, but it’s a huge engineering challenge.
Instead of just cooling the spacecraft with liquid helium like they did with Spitzer, they’ll need to take the heat out in stages, with reflectors, radiators, and finally a cryocooler around the instruments themselves.
With a huge, cold infrared telescope, Origins will push beyond James Webb’s view of the formation of the first galaxies. It’ll look to the era when the first stars were forming, a time that astronomers call the Dark Ages.
It’ll see the formation of planetary systems, dust disks and directly observe the atmospheres of other planets looking for biosignatures, evidence of life out there.
Three exciting missions, that’ll push our knowledge of the Universe forward. But I’ve saved the biggest, most ambitious telescope for last
LUVOIR, or the Large UV/Optical/IR Surveyor. James Webb is going to be a powerful telescope, but it’s an infrared instrument designed to look at cooler objects in the Universe, like red-shifted galaxies at the beginning of time, or newly forming planetary systems. The Origins Space Telescope will be a better version of James Webb.
LUVOIR will be the true successor to the Hubble Space Telescope. It’ll be a huge instrument capable of seeing in infrared, visible light and ultraviolet.
Artist’s concept of the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) space telescope. Credits: NASA/GSFC
There are two designs in the works. One which is 8-meters across and could launch on a heavy-lift vehicle like the Falcon Heavy. And another design that would use the Space Launch System that measures 15-meters across. That’s 50% bigger than the biggest Earth-based telescope. Remember, Hubble is only 2.6 meters.
It’ll have a wide field of view and a suite of filters and instruments that astronomers can use to observe whatever they want. It’ll be equipped with a coronograph like we talked about earlier, to directly observe planets and obscure their stars, a spectrograph to figure out what chemicals are present in exoplanet atmospheres, and more.
LUVOIR will be a general purpose instrument, which astronomers will use to make discoveries across the fields of astrophysics and planetary science. But some of its capabilities will include: directly observing exoplanets and searching for biosignatures, categorizing all the different kinds of exoplanets out there, from hot Jupiters to super Earths.
It’ll be able to observe objects within the Solar System better than anything else – if we don’t have a spacecraft there, LUVOIR will be a pretty good view. For example, here’s a view of Enceladus from Hubble, compared to the view from LUVOIR.
Enceladus seen from Hubble and LUVOIR. Credit: NASA
It will be able to look out anywhere in the Universe, to see much smaller structures than Hubble. It’ll see the first galaxies, first stars, and help measure the concentrations of dark matter across the Universe.
Astronomers still don’t fully understand what happens when stars gather enough mass to ignite. LUVOIR will look into star forming regions, peer through the gas and dust and see the earliest moments of star formation as well as the planets orbiting them.
Have I got you totally and completely excited about the future of astronomy? Good. But here’s comes the bad news. There’s almost no chance reality will match this fantasy.
Earlier this month NASA announced that mission planners working on these space telescopes will need to limit their budgets to between three and five billion dollars. Until now, planners didn’t have any guidelines, they were to just design instruments that could get the science done.
Engineers had been working on mission plans that could easily cross $5 billion for HabEx, Lynx and OST, and were considering a much larger $20 billion for LUVOIR.
Even though Congress has been pushing for surprisingly big budgets for NASA, the space agency wants its planners to be conservative. And when you consider just how over budget and late James Webb has become, it’s not entirely surprising.
James Webb was originally supposed to cost between one and three point five billion dollars and launch between 2007 and 2011. Now it looks like 2020 for a launch, the costs have broken past a Congress mandated $8.8 billion budget, and it’s clear there’s still a lot of work to be done.
In a recent shake test, engineers found washers and screws that had shaken out of the telescope. This isn’t like an IKEA shelf with leftover parts. These pieces are important.
Even though it’s been saved from the chopping block, the WFIRST Telescope is estimated to be $3.9 billion, up from its original $2 billion budget.
One, two or maybe even all of these telescopes will eventually get built. This is what the scientists think are most important to make the next discoveries in astronomy, but get ready for budget battles, cost overruns and stretching timelines. We’ll know better when all the studies come together in 2019.
It would take some kind of engineering miracle to have all four telescopes come together, on time and on budget, to blast to space together in 2035. I’ll keep you updated.
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Stella Kafka is the Director of the American Association of Variable Star Observers.
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This global map of Mars shows a growing dust storm as of June 6, 2018. The map was produced by the Mars Color Imager (MARCI) camera on NASA's Mars Reconnaissance Orbiter spacecraft. The blue dot indicates the approximate location of Opportunity. Image Credit: NASA/JPL-Caltech/MSSS
NASA’s Opportunity mission can rightly be called the rover that just won’t quit. Originally, this robotic rover was only meant to operate on Mars for 90 Martian days (or sols), which works out to a little over 90 Earth days. However, since it made its landing on January 25th, 2004, it has remained in operation for 14 years, 4 months, and 18 days – exceeding its operating plan by a factor of 50!
However, a few weeks ago, NASA received disturbing news that potentially posed a threat to the “little rover that could”. A Martian storm, which has since grown to occupy an area larger than North America – 18 million km² (7 million mi²) – was blowing in over rover’s position in the Perseverance Valley. Luckily, NASA has since made contact with the rover, which is encouraging sign.
NASA’s Mars Reconnaissance Orbiter first detected the storm on Friday, June 1st, and immediately notified the Opportunity team to begin preparing contingency plans. The storm quickly grew over the next few days and resulted in dust clouds that raised the atmosphere’s opacity, which blocked out most of the sunlight from reaching the surface. This is bad news for the rover since it relies on solar panels for power and to recharge its batteries.
Artist’s conception of a Mars Exploration Rover, which included Opportunity and Spirit. Credit: NASA
By Wednesday, June 6th, Opportunity’s power levels had dropped significantly and the rover was required to shift to minimal operations. But beyond merely limiting the rover’s operations, a prolonged dust storm also means that the rover might not be able to keep its energy-intensive survival heaters running – which protect its batteries from the extreme cold of Mars’ atmosphere.
The Martian cold is believed to be what resulted in the loss of the Spirit rover in 2010, Opportunity’s counterpart in the Mars Exploration Rover mission. Much like Opportunity, Spirit‘s mission as only meant to last for 90 days, but the rover managed to remain in operation for 2269 days (2208 sols) from start to finish. It’s also important to note that Opportunity has dealt with long-term storms before and emerged unscathed.
Back in 2007, a much larger storm covered the planet, which led to two weeks of minimal operations and no communications. However, the current storm has intensified as of Sunday morning (June 10th), creating a perpetual state of night over the rover’s location in Perseverance Valley and leading to a level of atmospheric opacity that is much worse than the 2007 storm.
Whereas the previous storm had an opacity level (tau) of about 5.5, this new storm has an estimated tau of 10.8. Luckily, NASA engineers received a transmission from the rover on Sunday, which was a positive indication since it proved that the rover still has enough battery charge to communicate with controllers at NASA’s Jet Propulsion Laboratory. This latest transmission also showed that the rover’s temperature had reached about -29 °C (-20 °F).
This 30-day time-lapse of the Martian atmosphere was capture by Opportunity during the 2007 dust storm. Credit: NASA/JPL-Caltech/Cornell
Full dust storms like this and the one that took place in 2007 are rare, but not surprising. They occur during summer in the southern hemisphere, when sunlight warms dust particles and lifts them higher into the atmosphere, creating more wind. That wind kicks up yet more dust, creating a feedback loop that NASA scientists are still trying to understand. While they can begin suddenly, they tend to last on the order of weeks or even months.
A saving grace about these storms is that they limit the extreme temperature swings, and the dust they kick up can also absorb solar radiation, thus raising ambient temperatures around Opportunity. In the coming weeks, engineers at the JPL will continue to monitor the rover’s power levels and ensure that it maintains the proper balance to keep its batteries in working order.
In the meantime, Opportunity’s science operations remain suspended and the Opportunity team has requested additional communications coverage from NASA’s Deep Space Network – the global system of antennas that communicates with all of the agency’s deep space missions. And if there’s one thing Opportunity has proven, it is that it’s capable of enduring!
Fingers crossed the storm subsides as soon as possible and the little rover that could once again emerges unscathed. At this rate, it could have many more years of life left in it!
