The Small Magellanic Cloud is one of the highlights of the southern sky. It can be seen with the naked eye. But it is obscured by clouds of interstellar gas and dust, which makes it hard for optical telescopes to get a good look at it. This image, taken with the ESO's VISTA. is the biggest-ever image of the SMC, and shows millions of stars. Credit: ESO/VISTA VMC
The Small Magellanic Cloud (SMC) galaxy. Credit: ESA/VISTA
The Small Magellanic Cloud (SMC) is one of the Milky Way’s nearest companions (along with the Large Magellanic Cloud.) It’s visible with the naked eye in the southern hemisphere. A new image from the European Southern Observatory’s (ESO) Visible and Infrared Survey Telescope for Astronomy (VISTA) has peered through the clouds that obscure it and given us our biggest image ever of the dwarf galaxy.
The SMC contains several hundred million stars, is about 7,000 light years in diameter, and is about 200,000 light years away. It’s one of the most distant objects that we can see with the naked eye, and can only be seen from the southern hemisphere (and the lowest latitudes of the northern hemisphere.)
The Small Magellanic Cloud is located in the Tucana constellation (The Toucan) in the southern hemisphere. The SMC is shown in green outline around the word ‘Tucana’. Also shown are NGC 104 and NGC 362, unrelated objects that are much closer to Earth. Image: ESO, IAU and Sky & Telescope
The SMC is a great target for studying how stars form because it’s so close to Earth, relatively speaking. But the problem is, its detail is obscured by clouds of interstellar gas and dust. So an optical survey of the Cloud is difficult.
But the ESO’s VISTA instrument is ideal for the task. VISTA is a near-infrared telescope, and infrared light is not blocked by the dust. VISTA was built at the ESO’s Paranal Observatory, in the Atacama Desert in Chile where it enjoys fantastic observing conditions. VISTA was designed to perform several surveys, including the Vista Magellanic Survey.
Explore the Zoomable image of the Small Magellanic Cloud. (You won’t be disappointed.)
The VISTA Magellanic Survey is focused on 3 main objectives:
The study of stellar populations in the Magellanic Clouds
The history of star formation in the Magellanic Clouds
The three-dimensional structure of the Magellanic Clouds
An international team led by Stefano Rubele of the University of Padova has studied this image, and their work has produced some surprising results. VISTA has shown us that most of the stars in this image are much younger than stars in other neighbouring galaxies. It’s also shown us that the SMC’s morphology is that of a warped disc. These are only early results, and there’s much more work to be done analyzing the VISTA image.
VISTA inside its enclosure at Paranal. VISTA has a 4.1 meter mirror, and its job is to survey large sections of the sky at once. In the background is the ESO’s Very Large Telescope. Image: G. Hüdepohl (atacamaphoto.com)/ESO
As the authors say in their paper, the SMC is a great target for study because of its “rich population of star clusters, associations, stellar pulsators, primary distance indicators, and stars in shortlived evolutionary stages.” In a way, we’re fortunate to have the SMC so close. But studying the SMC was difficult, until the VISTA came online with its infrared capabilities.
VISTA saw first light on December 11th, 2009. It’s time is devoted to systematic surveys of the sky. In its first five years, it has undertaken large surveys of the entire southern sky, and also studied small patches of the sky to discern extremely faint objects. The leading image in this article is from the Vista Magellanic Survey, a survey covering 184 square degrees of the sky, taking in both the Small Magellanic Cloud and the Large Magellanic Cloud, and their environment.
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
We humans have an insatiable hunger to understand the Universe. As Carl Sagan said, “Understanding is Ecstasy.” But to understand the Universe, we need better and better ways to observe it. And that means one thing: big, huge, enormous telescopes.
In this series we’ll look at the world’s upcoming Super Telescopes:
It’s easy to forget the impact that the Hubble Space Telescope has had on our state of knowledge about the Universe. In fact, that might be the best measurement of its success: We take the Hubble, and all we’ve learned from it, for granted now. But other space telescopes are being developed, including the WFIRST, which will be much more powerful than the Hubble. How far will these telescopes extend our understanding of the Universe?
“WFIRST has the potential to open our eyes to the wonders of the universe, much the same way Hubble has.” – John Grunsfeld, NASA Science Mission Directorate
The WFIRST might be the true successor to the Hubble, even though the James Webb Space Telescope (JWST) is often touted as such. But it may be incorrect to even call WFIRST a telescope; it’s more accurate to call it an astrophysics observatory. That’s because one of its primary science objectives is to study Dark Energy, that rather mysterious force that drives the expansion of the Universe, and Dark Matter, the difficult-to-detect matter that slows that expansion.
WFIRST will have a 2.4 meter mirror, the same size as the Hubble. But, it will have a camera that will expand the power of that mirror. The Wide Field Instrument is a 288-megapixel multi-band near-infrared camera. Once it’s in operation, it will capture images that are every bit as sharp as those from Hubble. But there is one huge difference: The Wide Field Instrument will capture images that cover over 100 times the sky that Hubble does.
Alongside the Wide Field Instrument, WFIRST will have the Coronagraphic Instrument. The Coronagraphic Instrument will advance the study of exoplanets. It’ll use a system of filters and masks to block out the light from other stars, and hone in on planets orbiting those stars. This will allow very detailed study of the atmospheres of exoplanets, one of the main ways of determining habitability.
WFIRST is slated to be launched in 2025, although it’s too soon to have an exact date. But when it launches, the plan is for WFIRST to travel to the Sun-Earth LaGrange Point 2 (L2.) L2 is a gravitationally balanced point in space where WFIRST can do its work without interruption. The mission is set to last about 6 years.
Probing Dark Energy
“WFIRST has the potential to open our eyes to the wonders of the universe, much the same way Hubble has,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate at Headquarters in Washington. “This mission uniquely combines the ability to discover and characterize planets beyond our own solar system with the sensitivity and optics to look wide and deep into the universe in a quest to unravel the mysteries of dark energy and dark matter.”
In a nutshell, there are two proposals for what Dark Energy can be. The first is the cosmological constant, where Dark Energy is uniform throughout the cosmos. The second is what’s known as scalar fields, where the density of Dark Energy can vary in time and space.
We used to think that the Universe expanded at a steady rate. Then in the 1990s we discovered that the expansion had accelerated. Dark Energy is the name given to the force driving that expansion. Image: NASA/STSci/Ann Feild
Since the 1990s, observations have shown us that the expansion of the Universe is accelerating. That acceleration started about 5 billion years ago. We think that Dark Energy is responsible for that accelerated expansion. By providing such large, detailed images of the cosmos, WFIRST will let astronomers map expansion over time and over large areas. WFIRST will also precisely measure the shapes, positions and distances of millions of galaxies to track the distribution and growth of cosmic structures, including galaxy clusters and the Dark Matter accompanying them. The hope is that this will give us a next level of understanding when it comes to Dark Energy.
If that all sounds too complicated, look at it this way: We know the Universe is expanding, and we know that the expansion is accelerating. We want to know why it’s expanding, and how. We’ve given the name ‘Dark Energy’ to the force that’s driving that expansion, and now we want to know more about it.
Probing Exoplanets
Dark Energy and the expansion of the Universe is a huge mystery, and a question that drives cosmologists. (They really want to know how the Universe will end!) But for many of the rest of us, another question is even more compelling: Are we alone in the Universe?
There’ll be no quick answer to that one, but any answer we find begins with studying exoplanets, and that’s something that WFIRST will also excel at.
Artist’s concept of the TRAPPIST-1 star system, an ultra-cool dwarf that has seven Earth-size planets orbiting it. We’re going to keep finding more and more solar systems like this, but we need observatories like WFIRST to understand the planets better. Credits: NASA/JPL-Caltech
“WFIRST is designed to address science areas identified as top priorities by the astronomical community,” said Paul Hertz, director of NASA’s Astrophysics Division in Washington. “The Wide-Field Instrument will give the telescope the ability to capture a single image with the depth and quality of Hubble, but covering 100 times the area. The coronagraph will provide revolutionary science, capturing the faint, but direct images of distant gaseous worlds and super-Earths.”
“The coronagraph will provide revolutionary science, capturing the faint, but direct images of distant gaseous worlds and super-Earths.” – Paul Hertz, NASA Astrophysics Division
The difficulty in studying exoplanets is that they are all orbiting stars. Stars are so bright they make it impossible to see their planets in any detail. It’s like staring into a lighthouse miles away and trying to study an insect near the lighthouse.
The Coronagraphic Instrument on board WFIRST will excel at blocking out the light of distant stars. It does that with a system of mirrors and masks. This is what makes studying exoplanets possible. Only when the light from the star is dealt with, can the properties of exoplanets be examined.
This will allow detailed measurements of the chemical composition of an exoplanet’s atmosphere. By doing this over thousands of planets, we can begin to understand the formation of planets around different types of stars. There are some limitations to the Coronagraphic Instrument, though.
The Coronagraphic Instrument was kind of a late addition to WFIRST. Some of the other instrumentation on WFIRST isn’t optimized to work with it, so there are some restrictions to its operation. It will only be able to study gas giants, and so-called Super-Earths. These larger planets don’t require as much finesse to study, simply because of their size. Earth-like worlds will likely be beyond the power of the Coronagraphic Instrument.
These limitations are no big deal in the long run. The Coronagraph is actually more of a technology demonstration, and it doesn’t represent the end-game for exoplanet study. Whatever is learned from this instrument will help us in the future. There will be an eventual successor to WFIRST some day, perhaps decades from now, and by that time Coronagraph technology will have advanced a great deal. At that future time, direct snapshots of Earth-like exoplanets may well be possible.
But maybe we won’t have to wait that long.
Starshade To The Rescue?
There is a plan to boost the effectiveness of the Coronagraph on WFIRST that would allow it to image Earth-like planets. It’s called the EXO-S Starshade.
The EXO-S Starshade is a 34m diameter deployable shading system that will block starlight from impairing the function of WFIRST. It would actually be a separate craft, launched separately and sent on its way to rendezvous with WFIRST at L2. It would not be tethered, but would orient itself with WFIRST through a system of cameras and guide lights. In fact, part of the power of the Starshade is that it would be about 40,000 to 50,000 km away from WFIRST.
Dark Energy and Exoplanets are priorities for WFIRST, but there are always other discoveries awaiting better telescopes. It’s not possible to predict everything that we’ll learn from WFIRST. With images as detailed as Hubble’s, but 100 times larger, we’re in for some surprises.
“This mission will survey the universe to find the most interesting objects out there.” – Neil Gehrels, WFIRST Project Scientist
“In addition to its exciting capabilities for dark energy and exoplanets, WFIRST will provide a treasure trove of exquisite data for all astronomers,” said Neil Gehrels, WFIRST project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This mission will survey the universe to find the most interesting objects out there.”
With all of the Super Telescopes coming on line in the next few years, we can expect some amazing discoveries. In 10 to 20 years time, our knowledge will have advanced considerably. What will we learn about Dark Matter and Dark Energy? What will we know about exoplanet populations?
Right now it seems like we’re just groping towards a better understanding of these things, but with WFIRST and the other Super Telescopes, we’re poised for more purposeful study.
The prototype greenhouse is being designed to provide astronauts with a continuous vegetarian diet. Image: University of Arizona.
NASA is all about solving challenges, and the goal of having a prolonged presence in space, or a colony on Mars or some other world, is full of challenges, including the necessity of growing food. Scientists at Kennedy Advanced Life Support Research are working on the Prototype Lunar/Mars Greenhouse Project to try and meet that challenge.
The Prototype Lunar/Mars Greenhouse Project (PLMGP) is all about growing vegetables for astronauts during extended stays on the Moon, on Mars, or anywhere they can’t be resupplied from Earth. Beyond growing food, the Project aims to understand how food-growing systems can also be a part of life-support systems.
“The approach uses plants to scrub carbon dioxide, while providing food and oxygen.” – Dr. Ray Wheeler
“We’re working with a team of scientists, engineers and small businesses at the University of Arizona to develop a closed-loop system. The approach uses plants to scrub carbon dioxide, while providing food and oxygen,” said Dr. Ray Wheeler, lead scientist in Kennedy Advanced Life Support Research.
The prototype itself is an inflatable, deployable system that researchers call a bioregenerative life support system. As crops are grown, the system recycles, water, recycles waste, and revitalizes the air.
The system is hydroponic, so no soil is needed. Water that is either brought along on missions or gathered in situ—on the Moon or at Mars for example—is enriched with nutrient salts, and flows continuously through plant root systems. Air in the system is recycled too. Astronauts exhale carbon dioxide, which plants absorb. Through photosynthesis, the plants produce oxygen for the astronauts.
This 18 foot long tube is a prototype of a bioregenerative life support system. The system grows crops, but also regenerates water and air. It’s at the University of Arizona’s Controlled Environment Agriculture Center. Image: University of Arizona
“We’re mimicking what the plants would have if they were on Earth and make use of these processes for life support,” said Dr. Gene Giacomelli, director of the Controlled Environment Agriculture Center at the University of Arizona. “The entire system of the lunar greenhouse does represent, in a small way, the biological systems that are here on Earth.”
“The entire system of the lunar greenhouse does represent, in a small way, the biological systems that are here on Earth.” – Dr. Gene Giacomelli
A key part of a system like this is knowing what astronauts will have to bring with them, and what resources they can find at their destination. This includes which type of plants and seeds will be needed, as well as how much water might be available once astronauts reach their destination. Methods of extracting water on Mars or the Moon are also being researched and developed.
Even if the necessary water can be found in situ on Mars and the Moon, that hardly means those are easy places to grow food. Astronauts have to be protected from radiation, and so will crops. These greenhouse chambers would have to buried underground, which means specialized lighting systems are also required.
“We’ve been successful in using electric LED (light emitting diode) lighting to grow plants,” Dr. Wheeler said. “We also have tested hybrids using both natural and artificial lighting.” Solar light could be captured with light concentrators that track the sun and then convey the light to the chamber using fiber optic bundles.
These systems are not NASA’s first experience at growing crops in space. Experiments aboard the International Space Station (ISS) have been an important part of the research into crop production in non-terrestrial environments. The Veggie Plant Growth System was NASA’s first attempt, and astronauts successfully harvested lettuce from that system.
NASA astronaut Shane Kimbrough harvesting lettuce from ‘VEGGIE’ on the International Space Station. Image: NASA
Earth has well-established systems for sustaining life, and this project is all about taking some of that to distant destinations in space.
“I think it’s interesting to consider that we’re taking our terrestrial companions with us,” Wheeler said. “While there may be ways to engineer around it in terms of stowage and resupply, it wouldn’t be as sustainable. The greenhouses provide a more autonomous approach to long-term exploration on the moon, Mars and beyond.”
New results from ALICE at the Large Hadron Collider show so-called strange hadrons being created where none were expected. As the number of proton-proton collisions (the blue lines) increase, the more of these strange hadrons are seen (as shown by the red squares in the graph). (Image: CERN)
There are some strange results being announced in the physics world lately. A fluid with a negative effective mass, and the discovery of five new particles, are all challenging our understanding of the universe.
New results from ALICE (A Large Ion Collider Experiment) are adding to the strangeness.
ALICE is a detector on the Large Hadron Collider (LHC). It’s one of seven detectors, and ALICE’s role is to “study the physics of strongly interacting matter at extreme energy densities, where a phase of matter called quark-gluon plasma forms,” according to the CERN website. Quark-gluon plasma is a state of matter that existed only a few millionths of a second after the Big Bang.
In what we might call normal matter—that is the familiar atoms that we all learn about in high school—protons and neutrons are made up of quarks. Those quarks are held together by other particles called gluons. (“Glue-ons,” get it?) In a state known as confinement, these quarks and gluons are permanently bound together. In fact, quarks have never been observed in isolation.
A cut-away view of the ALICE detector at CERN’s LHC. Image: By Pcharito – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31365856
The LHC is used to collide particles together at extremely high speeds, creating temperatures that can be 100,000 times hotter than the center of our Sun. In new results just released from CERN, lead ions were collided, and the resulting extreme conditions come close to replicating the state of the Universe those few millionths of a second after the Big Bang.
In those extreme temperatures, the state of confinement was broken, and the quarks and gluons were released, and formed quark-gluon plasma.
So far, this is pretty well understood. But in these new results, something additional happened. There was increased production of what are called “strange hadrons.” Strange hadrons themselves are well-known particles. They have names like Kaon, Lambda, Xi and Omega. They’re called strange hadrons because they each have one “strange quark.”
If all of this seems a little murky, here’s the dinger: Strange hadrons may be well-known particles, because they’ve been observed in collisions between heavy nuclei. But they haven’t been observed in collisions between protons.
“Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system…opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.” – Federico Antinori, Spokesperson of the ALICE collaboration.
“We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”
Enhanced Strangeness?
The creation of quark-gluon plasma at CERN provides physicists an opportunity to study the strong interaction. The strong interaction is also known as the strong force, one of the four fundamental forces in the Universe, and the one that binds quarks into protons and neutrons. It’s also an opportunity to study something else: the increased production of strange hadrons.
In a delicious turn of phrase, CERN calls this phenomenon “enhanced strangeness production.” (Somebody at CERN has a flair for language.)
Enhanced strangeness production from quark-gluon plasma was predicted in the 1980s, and was observed in the 1990s at CERN’s Super Proton Synchrotron. The ALICE experiment at the LHC is giving physicists their best opportunity yet to study how proton-proton collisions can have enhanced strangeness production in the same way that heavy ion collisions can.
According to the press release announcing these results, “Studying these processes more precisely will be key to better understand the microscopic mechanisms of the quark-gluon plasma and the collective behaviour of particles in small systems.”
A new study looked at 52 submillimeter galaxies to help us understand the early ages of our Universe. Image: University of Nottingham/Omar Almaini
In order to make sense of our Universe, astronomers have to work hard, and they have to push observing technology to the limit. Some of that hard work revolves around what are called sub-millimeter galaxies (SMGs.) SMGs are galaxies that can only be observed in the submillimeter range of the electromagnetic spectrum.
The sub-millimeter range is the waveband between the far-infrared and microwave wavebands. (It’s also called Terahertz radiation.) We’ve only had the capability to observe in the sub-millimeter range for a couple decades. We’ve also increased the angular resolution of telescopes, which helps us discern separate objects.
The submillimter wavelength is also called Terahertz Radiation, and is between Infrared and Microwave Radiation on the spectrum. Image: By Tatoute, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6884073
SMGs themselves are dim in other wavelengths, because they’re obscured by dust. The optical light is blocked by the dust, and absorbed and re-emitted in the sub-millimeter range. In the sub-millimeter, SMGs are highly luminous; trillions of times more luminous than the Sun, in fact.
This is because they are extremely active star-forming regions. SMGs are forming stars at a rate hundreds of times greater than the Milky Way. They are also generally older, more distant galaxies, so they’re red-shifted. Studying them helps us understand galaxy and star formation in the early universe.
ALMA is an array of dishes located at the Atacama Desert in Chile. Image: ALMA (ESO/NAOJ/NRAO), O. Dessibourg
A new study, led by James Simpson of the University of Edinburgh and Durham University, has examined 52 of these galaxies. In the past, it was difficult to know the exact location of SMGs. In this study, the team relied on the power of the Atacama Large Millimeter/submillimeter array (ALMA) to get a much more precise measurement of their location. These 52 galaxies were first identified by the Submillimeter Common-User Bolometer Array (SCUBA-2) in the UKIDSS Ultra Deep Survey.
There are four major results of the study:
48 of the SMGs are non-lensed, meaning that there is no object of sufficient mass between us and them to distort their light. Of these, the team was able to constrain the red-shift (z) for 35 of them to a median range of z-2.65. When it comes to extra-galactic observations like this, the higher the red-shift, the further away the object is. (For comparison, the highest red-shift object we know of is a galaxy called GN-z11, at z=11.1, which corresponds to about 400 million years after the Big Bang.
Another type of galaxy, the Ultra-Luminous Infrared Galaxy (ULIRG) were thought to be evolved versions of SMGs. But this study showed that SMGs are larger and cooler than ULIRGs, which means that any evolutionary link between the two is unlikely.
The team calculated estimates of dust mass in these galaxies. Their estimates suggest that effectively all of the optical-to-near-infrared light from co-located stars is obscured by dust. They conclude that a common method in astronomy used to characterize astronomical light sources, called Spectral Energy Distribution (SED), may not be reliable when it comes to SMGs.
The fourth result is related to the evolution of galaxies. According to their analysis, it seems unlikely that SMGs can evolve into spiral or lenticular galaxies (a lenticular galaxy is midway between a spiral and an elliptical galaxy.) Rather, it appears that SMGs are the progenitors of elliptical galaxies.
The Pinwheel Galaxy (M101, NGC 5457) is a stunning example of a spiral galaxy. This study determines that there likely is no evolutionary link between sub-millimeter galaxies and spiral galaxies. Image: European Space Agency & NASA. CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=36216331
This study was a pilot study that the team hopes to extend to many other SMGs in the future.
This image taken by the Mars Reconnaissance Orbiter's HiRise camera shows the bright landing platform left behind by NASA's Mars Exploration Rover Opportunity when it landed in 2004. Opportunity landed on the surface of Mars and then bounced and tumbled into the Eagle Crater. The image was taken on April 8, 2017. Image: NASA/JPL-Caltech/Univ. of Arizona
NASA’s eagle-eyed Mars Reconnaissance Orbiter (MRO) has captured orbital images of Opportunity’s Hole-In-One landing site, smack dab in the middle of Eagle Crater on the surface of Mars.
Opportunity arrived at Mars on January 25th, 2005. It’s landing was slowed by parachute, and cushioned by airbags. Once it hit the surface, it bounced its way into “Eagle Crater“, a feature a mere 22 meters across. Not a bad shot!
This is the first color image that the High Resolution Imaging Science Experiment (HiRise) has captured of Opportunity’s landing site. It shows the remarkable landing site inside the crater, where the landing pad was left behind after Opportunity rolled off of it and got going. It also shows the rover’s parachute and backshell.
It’s amazing that, given the relatively smooth surface in Opportunity’s landing area, the rover came to rest inside a small crater. When Opportunity “woke up” at its landing site, its first images were of the inside of Eagle Crater. This was the first look we ever got at the sedimentary rocks on Mars, taken by the rover’s navigation camera.
Opportunity’s navigation camera took this picture, one of the rover’s first, of the inside of Eagle Crater. Exposed Martian rocks are visible. NASA/JPL
After leaving Eagle Crater, Opportunity took a look back and captured a panoramic image. Plainly visible is the rover’s landing pad, the exposed sedimentary rock, and the rover’s tracks in the Martian soil.
This panorama image, called “Lion King” was assembled from 558 images totalling over 75 megabytes. The rock outcrop, the landing pad, and the rover’s tracks are all clearly visible. Image: NASA/JPL/Cornell
MRO arrived at Mars a couple years later, and by that time Opportunity had already left its landing site and made its way south to the much larger Victoria Crater.
When the Mars Reconnaissance Orbiter arrived at Mars, 2 years after Opportunity touched down there, Opportunity had left Eagle Crater and travelled the 6 km to Victoria Crater. By NASA/JPL/University of Arizona – http://photojournal.jpl.nasa.gov/catalog/PIA08813, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4211043
Opportunity is still chugging along, doing valuable work. And so is the MRO and its HiRise instrument. At this point, Opportunity has to be considered one of the most successful scientific undertakings ever.
Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)
If we want to send spacecraft to exoplanets to search for life, we better get good at building submarines.
A new study by Dr. Fergus Simpson, of the Institute of Cosmos Sciences at the University of Barcelona, shows that our assumptions about exo-planets may be wrong. We kind of assume that exoplanets will have land masses, even though we don’t know that. Dr. Simpson’s study suggests that we can expect lots of oceans on the habitable worlds that we might discover. In fact, ocean coverage of 90% may be the norm.
At the heart of this study is something called ‘Bayesian Statistics’, or ‘Bayesian Probability.’
Normally, we give something a probability of occurring—in this case a habitable world with land masses—based on our data. And we’re more confident in our prediction if we have more data. So if we find 10 exoplanets, and 7 of them have significant land masses, we think there’s a 70% chance that future exoplanets will have significant land masses. If we find 100 exoplanets, and 70 of them have significant land masses, then we’re even more confident in our 70% prediction.
Is Earth in the range of normal when it comes to habitable planets? Or is it an outlier, with both large land masses, and large oceans? Image: Reto Stöckli, Nazmi El Saleous, and Marit Jentoft-Nilsen, NASA GSFC
But the problem is, even though we’ve discovered lots of exoplanets, we don’t know if they have land masses or not. We kind of assume they will, even though the masses of those planets is lower than we expect. This is where the Bayesian methods used in this study come in. They replace evidence with logic, sort of.
In Bayesian logic, probability is assigned to something based on the state of our knowledge and on reasonable expectations. In this case, is it reasonable to expect that habitable exoplanets will have significant landmasses in the same way that Earth does? Based on our current knowledge, it isn’t a reasonable expectation.
According to Dr. Simpson, the anthropic principle comes into play here. We just assume that Earth is some kind of standard for habitable worlds. But, as the study shows, that may not be the case.
“Based on the Earth’s ocean coverage of 71%, we find substantial evidence supporting the hypothesis that anthropic selection effects are at work.” – Dr. Fergus Simpson.
In fact, Earth may be a very finely balanced planet, where the amount of water is just right for there to be significant land masses. The size of the oceanic basins is in tune with the amount of water that Earth retains over time, which produces the continents that rise above the seas. Is there any reason to assume that other worlds will be as finely balanced?
Dr. Simpson says no, there isn’t. “A scenario in which the Earth holds less water than most other habitable planets would be consistent with results from simulations, and could help explain why some planets have been found to be a bit less dense than we expected.” says Simpson.
Simpson’s statistical model shows that oceans dominate other habitable worlds, with most of them being 90% water by surface area. In fact, Earth is very close to being a water world. The video shows what would happen to Earth’s continents if the amount of water increased. There is only a very narrow window in which Earth can have both large land masses, and large oceans.
Dr. Simpson suggests that the fine balance between land and water on Earth’s surface could be one reason we evolved here. This is based partly on his model, which shows that land masses will have larger deserts the smaller the oceans are. And deserts are not the most hospitable place for life, and neither are they biodiverse. Also, biodiversity on land is about 25 times greater than biodiversity in oceans, at least on Earth.
Simpson says that the fine balance between land mass and ocean coverage on Earth could be an important reason why we are here, and not somewhere else.
“Our understanding of the development of life may be far from complete, but it is not so dire that we must adhere to the conventional approximation that all habitable planets have an equal chance of hosting intelligent life,” Simpson concludes.
Opportunity took this panorama shot of "Rocheport Ridge" as it left Cape Tribulation. Rocheport is on the southern end of Cape Tribulation. Image:NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
You’d have to be an intrepid explorer to investigate something named ‘Cape Tribulation’. Opportunity, NASA’s long-lived rover on Mars’ surface, has been just that. But Opportunity is now leaving Cape Tribulation behind, after being in that area since late 2014, or for about 30 months.
Cape Tribulation is the name given to a segment of crater rim at Endeavour Crater, where Opportunity has been for over 5 1/2 years. During that time, Opportunity reached some important milestones. While there, it surpassed 26 miles in distance travelled, the length of a marathon race. It also reached its highest elevation yet, and in ‘Marathon Valley’, it investigated clay outcrops seen from orbit. Opportunity also had some struggles there, when its flash memory stopped working, meaning all data had to be transmitted every day, or lost.
Sol 3906, January 19, 2015. Summit panorama from Cape Tribulation from the Opportunity Mars Rover. Credit: NASA/Arizona State University.
Before reaching Cape Tribulation 30 months ago, Opportunity investigated other parts of Endeavour Crater called “Cape York,” “Solander Point” and “Murray Ridge.”
Some of the named features at Endeavour Crater. Image: NASA/JPL-Caltech/MSSS
The rover’s next destination is Perseverance Valley, where it will investigate how it was carved out billions of years ago: by water, by wind, or perhaps flowing material lubricated by water. Before leaving Cape Tribulation, Opportunity captured the panoramic image of Rochefort Ridge, a section of the Endeavour Crater rim marked by grooves on its side.”The degree of erosion at Rocheport is fascinating,” said Opportunity Deputy Principal Investigator Ray Arvidson, of Washington University in St. Louis. “Grooves run perpendicular to the crest line. They may have been carved by water or ice or wind. We want to see as many features like this on the way to Perseverance Valley as we can, for comparison with what we find there.”
Endeavour crater is about 22km in diameter, and Perseverance Valley is about 2 football fields long. The goal at Endeavour is to investigate its segmented rim, where the oldest rocks ever investigated on Mars are exposed. Since the beginning of April, Opportunity has travelled about 98 meters, to a point where Cape Tribulation meets the plain around the crater.
“From the Cape Tribulation departure point, we’ll make a beeline to the head of Perseverance Valley…” – Opportunity Deputy Principal Investigator Ray Arvidson
“From the Cape Tribulation departure point, we’ll make a beeline to the head of Perseverance Valley, then turn left and drive down the full length of the valley, if we can,” Arvidson said. “It’s what you would do if you were an astronaut arriving at a feature like this: Start at the top, looking at the source material, then proceed down the valley, looking at deposits along the way and at the bottom.”
It’s the nature of those deposits that can give vital clues to how Perseverance Valley was formed. Arvidson said, “If it was a debris flow, initiated by a little water, with lots of rocks moving downhill, it should be a jumbled mess. If it was a river cutting a channel, we may see gravel bars, crossbedding, and what’s called a ‘fining upward’ pattern of sediments, with coarsest rocks at the bottom.”
Opportunity, and its sister rover Spirit, arrived at Mars in 2004, with a planned mission length of 90 days. Opportunity has surpassed that by over 12 years, and continues to perform extremely well in the Martian environment.
The appearing and disappearing feature observed in Titan's Lakes was dubbed "Magic Island". Image: NASA/JPL-Caltech/ASI/Cornell
Saturn’s largest Moon, Titan, is the only other world in our Solar System that has stable liquid on its surface. That alone, and the fact that the liquid is composed of methane, ethane, and nitrogen, makes it an object of fascination. The bright spot features that Cassini observed in the methane seas that dot the polar regions only deepen the fascination.
A new paper published in Nature Astronomy digs deeper into a phenomenon in Titan’s seas that has been puzzling scientists. In 2013, Cassini noticed a feature that wasn’t there on previous fly-bys of the same region. In subsequent images, the feature had disappeared again. What could it be?
One explanation is that the feature could be a disappearing island, rising and falling in the liquid. This idea took hold, but was only an initial guess. Adding to the mystery was the doubling in size of these potential islands. Others speculated that they could be waves, the first waves observed anywhere other than on Earth. Binding all of these together was the idea that the appearance and disappearance could be caused by seasonal changes on the moon.
Titan’s dense, hydrocarbon rich atmosphere remains a focal point of scientific research. Credit: NASA
Now, scientists at NASA’s Jet Propulsion Laboratory (JPL) think they know what’s behind these so-called ‘disappearing islands,’ and it seems like they are related to seasonal changes.
The study was led by Michael Malaska of JPL. The researchers simulated the frigid conditions on Titan, where the temperature is -179.2 Celsius. At that temperature, some interesting things happen to the nitrogen in Titan’s atmosphere.
On Titan, it rains. But the rain is composed of extremely cold methane. As that methane falls to the surface, it absorbs significant amounts of nitrogen from the atmosphere. The rain hits Titan’s surface and collects in the lakes on the moon’s polar regions.
The researchers manipulated the conditions in their experiments to mirror the changes that occur on Titan. They changed the temperature, the pressure, and the methane/ethane composition. As they did so, they found that nitrogen bubbled out of solution.
“Our experiments showed that when methane-rich liquids mix with ethane-rich ones — for example from a heavy rain, or when runoff from a methane river mixes into an ethane-rich lake — the nitrogen is less able to stay in solution,” said Michael Malaska of JPL. This release of nitrogen is called exsolution. It can occur when the seasons change on Titan, and the seas of methane and ethane experience a slight warming.
“Thanks to this work on nitrogen’s solubility, we’re now confident that bubbles could indeed form in the seas, and in fact may be more abundant than we’d expected,” said Jason Hofgartner of JPL, a co-author of the study who also works on Cassini’s radar team. These nitrogen bubbles would be very reflective, which explains why Cassini was able to see them.
The first-ever images of the surface of a new moon or planet are always exciting. The Huygens probe was launched from Cassini to the surface of Titan, but was not able investigate the lakes and seas on the surface. Image Credit: ESA/NASA/JPL/University of Arizona
The seas on Titan may be what’s called a prebiotic environment, where chemical conditions are hospitable to the appearance of life. Some think that the seas may already be home to life, though there’s no evidence of this, and Cassini wasn’t equipped to investigate that premise. Some experiments have shown that an atmosphere like Titan’s could generate complex molecules, and even the building blocks of life.
NASA and others have talked about different ways to explore Titan, including balloons, a drone, splashdown landers, and even a submarine. The submarine idea even received a NASA grant in 2015, to develop the idea further.
So, mystery solved, probably. Titan’s bright spots are neither islands nor waves, but bubbles.
Cassini’s mission will end soon, and it’ll be quite some time before Titan can be investigated further. The question of whether Titan’s seas are hospitable to the formation of life, or whether there may already be life there, will have to wait. What role the nitrogen bubbles play in Titan’s life question will also have to wait.
This illustration of a double-cylinder space colony is from the 1970's, by artist Rick Guidice. Image: NASA Ames Research Center
To some, art and science are opposed to one another. Art is aesthetics, expression, and intuition, while science is all cold, hard, rational thought. But that’s a simplistic understanding. They’re both quintessential human endeavours, and they’re both part of the human spirit.
Some at NASA have always understood this, and there’s actually an interesting, collaborative history between NASA and the art world, that reaches back several decades. Not the kind of art that you see hanging in elite galleries in the world’s large cities, but the kind of art that documents achievements in space exploration, and that helps us envision what our future could be.
Mitchell Jamieson produced this painting of astronaut Gordon Cooper. Titled “First Steps”, it documents Cooper’s first steps after exiting his Mercury spacecraft in 1963, after Cooper had completed 22 orbits of Earth. Image Credit: Mitchell Jamieson/Courtesy of the Smithsonian National Air and Space Museum
Back in 1962, when NASA was 4 years old, NASA administrator James Webb put the wheels in motion for a collaboration between NASA and American artists. Artist Bruce Stevenson had been commissioned to produce a portrait of Alan Shepard. Shepard, of course, was the first American in space. He piloted the first Project Mercury flight, MR-3, in 1961. When Webb saw it, he got a bright idea.
When Stevenson brought is portrait of Shepard to NASA headquarters, James Webb thought that Stevenson wanted to paint portraits of all seven Mercury astronauts. But Webb thought a group portrait would be even better. The group portrait was never produced, but it got Webb thinking. In a memo, he said “…we should consider in a deliberate way just what NASA should do in the field of fine arts to commemorate the …historic events” of the American space program.
That set in motion a framework that exists to this day. Beyond just portraits, Webb wanted artists to produce paintings that would convey the excitement around the entire endeavour of space flight, and what the deeper meaning behind it might be. He wanted artists to capture all of the excitement around the preparation and countdown for launches, and activities in space.
This 1963 painting by artist Paul Calle captures the lift-off of the Saturn V Moon rocket. Image: Paul Calle, NASA
That’s when the NASA collaboration with artists began. A young artist named James Dean was assigned to the program, and he took a page out of the Air Force’s book, which established its own art program in 1954.
There’s a whole cast of characters involved, each one contributing to the success of the program. One such person was John Walker, Director of the National Gallery. He was enthusiastic, saying in a talk in 1965 that “the present space exploration effort by the United States will probably rank among the more important events in the history of mankind.” History has certainly proven those words to be true.
This Norman Rockwell painting is from 1965, and shows astronauts Gus Grissom and John Young suiting up for the first Gemini flight in March, 1965. NASA loaned Rockwell a spacesuit for the painting. Image: Norman Rockwell, NASA Art Program
Walker went on to say that it was the artists’ job “…not only to record the physical appearance of the strange new world which space technology is creating, but to edit, select and probe for the inner meaning and emotional impact of events which may change the destiny of our race.”
And that’s what they did. Artists like Norman Rockwell, Andy Warhol, Peter Hurd, Annie Liebowitz, Robert Rauschenberg, and others, all took part in the program.
Artist Peter Hurd painted the launch of Skylab in 1973. Image Credit: Peter Hurd, Courtesy of National Air and Space Museum, Smithsonian Institution
In the 1970’s, thinkers like Gerard K. O’Neill began to formulate ideas of what human colonies in space might look like. NASA held a series of conferences where these ideas were shared and explored. Artists Rick Guidice and Don Davis created many paintings and illustrations of what colony designs like Bernal Spheres, Double Cylinders, and Toroidal Colonies might look like.
This piece by artist Don Davis depicts the end-cap of a cylindrical colony. Notice the suspension bridge, and people enjoying themselves by a river. Image: Don Davis, NASA Ames Research CenterThis cut-away image of a Bernal Sphere colony was created by artist Rick Guidice. Image: Rick Guidice, NASA Ames Research Center
NASA continues to work with artists, though the nature of the relationship has changed over the decades. Artists are often used to flesh out new discoveries when images are not available. Cassini’s so-called Grand Finale, when it will orbit between Saturn and its rings 22 times before crashing into the planet, was conceptualized by an unnamed artist.
An artist’s illustration of the Cassini probe’s Grand Finale. Image: NASA/JPL/CalTech
The recent discovery of the exoplanets in the TRAPPIST-1 system was huge news. It still is. But TRAPPIST-1 is over 40 light years away, and NASA relied on artists to bring the discovery to life. This illustration was widely used to help us understand what planets orbiting the TRAPPIST-1 Red Dwarf might look like.
Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech
NASA now has quite a history of relying on art to convey what words can’t do. Space colonies, distant solar systems, and spacecraft ending their missions on other worlds, have all relied on the work of artists. But if I had to choose a favorite, it would probably be the 1981 water color by artist Henry Casselli. It makes you wonder what it’s like for an individual to take part in these species-defining endeavours. Just one person, sitting, contemplating, and preparing.
This Henry Casselli watercolor shows astronaut John Young preparing for a launch on April 12, 1981. What must he have been thinking as he prepared for the first flight of the Space Shuttle Program? Image: Henry Casselli, Courtesy NASA Art Program
