Saturn's "UFO moon" Pan up close. Credit:
NASA/JPL/Space Science Institute
This new view of Saturn’s moon Pan is the closest yet, snapped by Cassini from a distance of 15,268 miles (24,572 km) on March 7, 2017. Pan measures 22 miles wide by 14 miles across and displays a number of small craters along with parallel ridges and grooves. Its broad, thinner equatorial ridge displays fine, parallel striations. Credit: NASA/JPL/Space Science Institute
Besides Earth, Saturn may be the only other planet where you can order rings with a side of ravioli. Closeup photos taken by the Cassini probe of the the planet’s second-innermost moon, Pan, on March 7 reveal remarkable new details that have us grasping at food analogies in a feeble attempt to describe its unique appearance.
A side view of Pan better shows its thin and wavy ridge likely built up through the accumulation of particles grabbed from Saturn’s rings. The ridge is between 0.9 and 2.5 miles (1-4 km) thick. Credit: NASA/JPL/Space Science Institute
As Pan moves along the Encke Gap its gravity creates ripples in Saturn’s A-ring. Credit: NASA/JPL/Space Science Institute
The two-part structure of the moon is immediately obvious: a core body with a thin, wavy ridge encircling its equator. How does such a bizarre object form in the first place? There’s good reason to believe that Pan was once part of a larger satellite that broke up near Saturn long ago. Much of the material flattened out to form Saturn’s rings while large shards like Pan and another ravioli lookalike, Atlas, orbited within or near the rings, sweeping up ring particles about their middles. Tellingly, the ridges are about as thick as the vertical distances each satellite travels in its orbit about the planet.
Pan casts its shadow on Saturn’s A-ring from within the 200-mile-wide (325 km) Encke Gap, which is maintained by the presence of the moon. Pan shares the gap with several diffuse ringlets from which it may still be gathering additional material around its equatorial ridge. Credit: NASA/JPL/Space Science Institute
Today, Pan orbits within and clears the narrow Encke Gap in Saturn’s outer A-ring of debris. It also helps create and shape the narrow ringlets that appear in the gap It’s lookalike cousin Atlas orbits just outside the A-ring.
Pan and Altas (25×22 miles) orbit within Saturn’s ring plane and may both be fragments from a larger moon breakup that created Saturn’s rings. Both have swept up material from the rings to form equatorial ridges. Credit: NASA/JPL/Space Science Institute
Moons embedded in rings can have profound effects on that material from clearing gaps to creating new temporary ringlets and raising vertical waves of material that rise above and below the ring plane. All these effects are produced by gravity, which gives even small objects like Pan dominion over surprisingly vast regions.
Enjoy this animated gif created from photos of the close flyby of Pan. Credit: NASA/JPL/Space Science Institute
Comet 2P Encke glides through Pisces on February 16th. Image credit and copyright: Hisayoshi Kato.
Comet 2P Encke glides through Pisces on February 16th. Image credit and copyright: Hisayoshi Kato.
Miss out on Comet 45/P Honda-Mrkos-Padadušáková last month? We’ll admit, it was fairly underwhelming in binoculars… but fear not, there are several other binocular comets in the pipeline for 2017.
Maybe you managed to catch sight of periodic Comet 2P Encke in late February after sunset before it disappeared into the Sun’s glare. Pronounced (En-Key), the comet actually passes through the field of view of the joint NASA/ESA Solar Heliospheric Observatory’s (SOHO) LASCO C3 camera from March 8th to March 14th before reemerging in the dawn sky.
I see you… Comet 2P Encke is now in SOHO’s LASCO C3 field of view, above Mercury (the bright object) moving in the opposite direction: pic.twitter.com/gcYwv0Sdkp
Northern hemisphere observers have already got a sneak peek at Encke’s performance low in the dusk in February as it heads towards perihelion. Now the comet heads southward, as it vaults up into the dawn sky for folks south of latitude 30 degrees north in mid-March. From latitude 30 degrees north, Encke will clear 15 degrees elevation above the southeastern horizon around March 31st. Viewers south of the equator will have a much better viewing prospect, as Encke glides southward through Aquarius. When will you first spot it?
The dawn path of 2P Encke through the first week of April as seen from latitude 30 degrees north. Credit: Starry Night.
Also: don’t forget to ‘spring forward’ to Daylight Saving Time this weekend for a majority of North America prior to beginning your dawn comet vigil… Europe and the United Kingdom gets a brief reprieve ’til March 26th.
Her are some upcoming key events for Comet 2P Encke:
Closest to Sun: March 10th, with a perihelion of 0.33 AU.
Closest to Earth: March 12th, at 0.65 AU distant.
Brightest: Around March 15. Encke is currently at magnitude +7, and should top out at magnitude +6, though it’ll only be 14 degrees from the Sun on this date.
This is Encke’s 63rd passage through the solar system since Pierre Méchain linked successive passages of the comet to the same in 1819. Like Edmond Halley, Encke didn’t discover the most famous of comets that now bears his name, but instead merely deduced its periodic nature. Halley was 1st, and Encke was second (hence the “2” in 2P…) The shortest short period comet, Encke was captured sometime thousands of years ago into its short period orbit, and is destined to burn out one day as it ventures from 4.1 to 0.33 AU from the Sun. Encke is also the source of the annual Taurid meteor shower in November, notable for producing a high rate of fireballs.
Comet 2P Encke on February 19th. Image credit and copyright: Cajun Astro.
Comets can be elusive beasties, as all of that precious quoted magnitude is smeared out over an extended surface area. Add on top this the fact that comets are also notorious for often under- and occasionally over-performing expectations. Just look at the ‘none more black’ albedo of comet 67P Churumov-Gerasimenkochronicled by ESA’s Rosetta spacecraft: it’s a miracle we can see ’em at all. And finally, that low contrast dawn sky can easily hide a faint binocular comet, fading it to invisibility. Start your comet vigil early, sweeping the horizon with binocs. An early start and a clear view are key. The slim waning crescent Moon sits 12 degrees north of Comet Encke on the morning of March 26th, and the comet also passes less than 3 degrees from the Helix Nebula (NGC 7293) on (no joke) April Fool’s Day April 1st.
The view on the morning of March 26th, 30 minutes before sunrise. Credit: Stellarium.
Flashback to one Encke orbit ago to 2013 and the comet provided a good dawn preshow to that biggest of cosmic let downs, Comet ISON. And although Encke makes its rounds every 3.3 years, orbital geometry assures that we won’t get another favorable viewing from Earth until 2036.
The orbit of 2P Encke. Credit NASA/JPL
Speaking of great comets that never were, we juuuust missed having a spectacular comet this past month, when recently discovered long-period Comet 2017 E1 Borisov passes just 0.045 AU (!) interior to our orbit. Unfortunately, this occurs five months too early, with the Earth almost exactly at the wrong place in its orbit. Now, if it was only August…
Comet Teaser for 2017
Yeah, the gambler’s fallacy would tell us that we’re due for the next great comet of the century, for sure. In the meantime, we’ve still got Comets 41P/Tuttle-Giacobini-Kresák (late March/April), C/2015 ER61 PanSTARRS (May), and C/2015 V2 Johnson (June) on tap as good binocular comets in 2017.
Be sure to enjoy elusive comet Encke as it flits once more though the dawn skies.
-Read about comets, occultations, eclipses and more for the year, in our new free e-book 101 Astronomical Events for 2017 out from Universe Today.
An artist's illustration of a light-sail powered by a radio beam (red) generated on the surface of a planet. Could the part of the beam that misses the sail be our mysterious Fast Radio Bursts? Image Credit: M. Weiss/CfA
The extremely energetic events that we see out there in the Universe are usually caused by cataclysmic astrophysical events and activities of one sort or another. But what about Fast Radio Bursts? A pair of astrophysicists at Harvard say that the seldom seen phenomena could, maybe, possibly, be evidence of an advanced alien technology.
Fast radio bursts (FRBs) are short-lived radio pulses that last only a few milliseconds. It’s been assumed that they have some astrophysical cause. Fewer than 2 dozen of them have been detected since their discovery in 2007. They’re detected by our huge radio telescopes like the Arecibo Observatory in Puerto Rico, and the Parkes Observatory in Australia. They’re extremely energetic, and their source is a great distance from us.
The NSF’s Arecibo Observatory, which is located in Puerto Rico, is the world largest radio telescope. Arecibo detected 11 FRBs over the course of 2 months. Credit: NAIC
The two astrophysicists, Avi Loeb at the Harvard-Smithsonian Center for Astrophysics, and Manasvi Lingam at Harvard University, decided to investigate the possibility that FRBs have an alien technological origin.
“Fast radio bursts are exceedingly bright given their short duration and origin at great distances, and we haven’t identified a possible natural source with any confidence. An artificial origin is worth contemplating and checking.” – Avi Loeb, Harvard-Smithsonian Center for Astrophysics
I’ll Take ‘Alien Signals’ For $200 Alex
Loeb and Lingam began by calculating how much energy would be needed to send a signal that strong across such an enormous distance. They found that doing so with solar energy requires a solar array with an area twice the surface area of Earth. That would be enough energy, if the alien civilization was as close as we are to a star similar to our Sun.
Obviously, such a massive construction project is well beyond us. But however unlikely it sounds, it can’t be ruled out.
The pair also asked themselves questions about the viability of such a project. Would the heat and energy involved in such a solar array melt the structure itself? Their answer is that water-cooling would be sufficient to keep an array like this operating.
Their next question was, “Why build something like this in the first place?”
I’ll Take ‘Alien Spacecraft Propulsion Systems’ For $400 Alex”
The thinking behind their idea is based on an idea that we ourselves have had: Could we power a spacecraft by pushing on it with lasers? Or Microwaves? If we’ve thought of it, why wouldn’t other existing civilizations? If another civilization were doing it, what would the technology look like?
Their investigation shows that the engineering they’re talking about could power a spacecraft with a payload of a million tons. That would be about 20 times bigger than our largest cruise ship. According to Lingam, “That’s big enough to carry living passengers across interstellar or even intergalactic distances.”
If FRBs are indeed the result of an alien propulsion system, here’s how it would work: Earth is rotating and orbiting, which means the alien star and galaxy are moving relative to us. That’s why we would only see a brief flash. The beam sweeps across the sky and only hits us for a moment. The repeated appearance of the FRB could be a clue to its alien, technological origin.
The authors of the study outlining this thinking know that it’s speculative. But it’s their job to speculate within scientific constraints, which they have done. As they say in the conclusion of their paper, “Although the possibility that FRBs are produced by extragalactic civilizations is more speculative than an astrophysical origin, quantifying the requirements necessary for an artificial origin serves, at the very least, the important purpose of enabling astronomers to rule it out with future data.”
There are other interpretations when it comes to FRBs, of course. The others of another paper say that for at least one group of FRBs, known as FRB 121102, the source is likely astrophysical. According to them, FRBs likely come from “a young, highly magnetized, extragalactic neutron star.”
Lurking behind these papers are some intriguing questions that are also fun to ponder.
If the system required a solar array twice the size of Earth, where would the materials come from? If the system required water-cooling to avoid melting, where would all the water come from? It’s impossible to know, or to even begin speculating. But a civilization able to do something like this would have to be master engineers and resource exploiters. That goes without saying.
Why they might do it is another question. Probably the same reasons we would: curiosity and exploration, or maybe to escape a dying world.
Artist's concept of a terraformed Mars (left) and an O'Neill Cylinder. Credit: Ittiz/Wikimedia Commons (left)/Rick Guidice/NASA Ames Research Center (right)
The idea of terraforming Mars – aka “Earth’s Twin” – is a fascinating idea. Between melting the polar ice caps, slowly creating an atmosphere, and then engineering the environment to have foliage, rivers, and standing bodies of water, there’s enough there to inspire just about anyone! But just how long would such an endeavor take, what would it cost us, and is it really an effective use of our time and energy?
Such were the questions dealt with by two papers presented at NASA’s “Planetary Science Vision 2050 Workshop” last week (Mon. Feb. 27th – Wed. Mar. 1st). The first, titled “The Terraforming Timeline“, presents an abstract plan for turning the Red Planet into something green and habitable. The second, titled “Mars Terraforming – the Wrong Way“, rejects the idea of terraforming altogether and presents an alternative.
The former paper was produced by Aaron Berliner from the University of California, Berkeley, and Chris McKay from the Space Sciences Division at NASA Ames Research Center. In their paper, the two researchers present a timeline for the terraforming of Mars that includes a Warming Phase and an Oxygenation Phase, as well as all the necessary steps that would precede and follow.
Artist’s impression of the terraforming of Mars, from its current state to a livable world. Credit: Daein Ballard
As they state in their paper’s Introduction:
“Terraforming Mars can be divided into two phases. The first phase is warming the planet from the present average surface temperature of -60° C to a value close to Earth’s average temperature to +15° C, and recreating a thick CO² atmosphere. This warming phase is relatively easy and quick, and could take ~100 years. The second phase is producing levels of O² in the atmosphere that would allow humans and other large mammals to breath normally. This oxygenation phase is relatively difficult and would take 100,000 years or more, unless one postulates a technological breakthrough.”
Before these can begin, Berliner and McKay acknowledge that certain “pre-terraforming” steps need to be taken. These include investigating Mars’ environment to determine the levels of water on the surface, the level of carbon dioxide in the atmosphere and in ice form in the polar regions, and the amount of nitrates in Martian soil. As they explain, all of these are key to the practicality of making a biosphere on Mars.
So far, the available evidence points towards all three elements existing in abundance on Mars. While most of Mars water is currently in the form of ice in the polar regions and polar caps, there is enough there to support a water cycle – complete with clouds, rain, rivers and lakes. Meanwhile, some estimates claim that there is enough CO² in ice form in the polar regions to create an atmosphere equal to the sea level pressure on Earth.
Nitrogen is also a fundamental requirement for life and necessary constituent of a breathable atmosphere, and recent data by the Curiosity Rover indicate that nitrates account for ~0.03% by mass of the soil on Mars, which is encouraging for terraforming. On top of that, scientists will need to tackle certain ethical questions related to how terraforming could impact Mars.
Artist’s concept of a possible Mars terraforming plant. Credit: National Geographic Channel
For instance, if there is currently any life on Mars (or life that could be revived), this would present an undeniable ethical dilemma for human colonists – especially if this life is related to life on Earth. As they explain:
“If Martian life is related to Earth life – possibly due to meteorite exchange – then the situation is familiar, and issues of what other types of Earth life to introduce and when must be addressed. However, if Martian life in unrelated to Earth life and clearly represents a second genesis of life, then significant technical and ethical issues are raised.”
To break Phase One – “The Warming Phase” – down succinctly, the authors address an issue familiar to us today. Essentially, we are altering our own climate here on Earth by introducing CO² and “super greenhouse gases” to the atmosphere, which is increasing Earth’s average temperature at a rate of many degrees centigrade per century. And whereas this has been unintentional on Earth, on Mars it could be re-purposed to deliberately warm the environment.
“The timescale for warming Mars after a focused effort of super greenhouse gas production is short, only 100 years or so,” they claim. “If all the solar incident on Mars were to be captured with 100% efficiency, then Mars would warm to Earth-like temperatures in about 10 years. However, the efficiency of the greenhouse effect is plausibly about 10%, thus the time it would take to warm Mars would be ~100 years.”
Mars’ south polar ice cap, as seen in April of 2000 by the Mars Odyssey mission. Credit: NASA/JPL/MSSS
Once this thick atmosphere has been created, the next step involves converting it into something breathable for humans – where O² levels would be the equivalent of about 13% of sea level air pressure here on Earth and CO² levels would be less than 1%. This phase, known as the “Oxygenation Phase”, would take considerably longer. Once again, they turn towards a terrestrial example to show how such a process could work.
Here on Earth, they claim, the high levels of oxygen gas (O²) and low levels of CO² are due to photosynthesis. These reactions rely on the sun’s energy to convert water and carbon dioxide into biomass – which is represented by the equation H²O + CO² = CH²O + O². As they illustrate, this process would take between 100,000 and 170,000 years:
“If all the sunlight incident on Mars was harnessed with 100% efficiency to perform this chemical transformation it would take only 17 years to produce high levels of O². However, the likely efficiency of any process that can transform H²O and CO² into biomass and O² is much less than 100%. The only example we have of a process that can globally alter the CO² and O² of an entire plant is global biology. On Earth the efficiency of the global biosphere in using sunlight to produced biomass and O2 is 0.01%. Thus the timescale for producing an O² rich atmosphere on Mars is 10,000 x 17 years, or ~ 170,000 years.”
However, they make allowances for synthetic biology and other biotechnologies, which they claim could increase the efficiency and reduce the timescale to a solid 100,000 years. In addition, if human beings could utilize natural photosynthesis (which has a comparatively high efficiency of 5%) over the entire planet – i.e. planting foliage all over Mars – then the timescale could be reduced to even a few centuries.
Finally, they outline the steps that need to be taken to get the ball rolling. These steps include adapting current and future robotic missions to assess Martian resources, mathematical and computer models that could examine the processes involved, an initiative to create synthetic organisms for Mars, a means to test terraforming techniques in a limited environment, and a planetary agreement that would establish restrictions and protections.
Quoting Kim Stanley Robinson, author of the Red Mars Trilogy, (the seminal work of science fiction about terraforming Mars) they issue a call to action. Addressing how long the process of terraforming Mars will take, they assert that we “might as well start now”.
To this, Valeriy Yakovlev – an astrophysicist and hydrogeologist from Laboratory of Water Quality in Kharkov, Ukraine – offers a dissenting view. In his paper, “Mars Terraforming – the Wrong Way“, he makes the case for the creation of space biospheres in Low Earth Orbit that would rely on artificial gravity (like an O’Neill Cylinder) to allow humans to grow accustomed to life in space.
Looking to one of the biggest challenges of space colonization, Yakovlev points to how life on bodies like the Moon or Mars could be dangerous for human settlers. In addition to being vulnerable to solar and cosmic radiation, colonists would have to deal with substantially lower gravity. In the case of the Moon, this would be roughly 0.165 times that which humans experience here on Earth (aka. 1 g), whereas on Mars it would be roughly 0.376 times.
Interior view of an O’Neill Cylinder. There are alternating strips of livable surface and “windows” to let light in. Credit: Rick Guidice/NASA Ames Research Center
The long-term effects of this are not known, but it is clear it would include muscle degeneration and bone loss. Looking farther, it is entirely unclear what the effects would be for those children who were born in either environment. Addressing the ways in which these could be mitigated (which include medicine and centrifuges), Yakovlev points out how they would most likely be ineffective:
“The hope for the medicine development will not cancel the physical degradation of the muscles, bones and the whole organism. The rehabilitation in centrifuges is less expedient solution compared with the ship-biosphere where it is possible to provide a substantially constant imitation of the normal gravity and the protection complex from any harmful influences of the space environment. If the path of space exploration is to create a colony on Mars and furthermore the subsequent attempts to terraform the planet, it will lead to the unjustified loss of time and money and increase the known risks of human civilization.”
In addition, he points to the challenges of creating the ideal environment for individuals living in space. Beyond simply creating better vehicles and developing the means to procure the necessary resources, there is also the need to create the ideal space environment for families. Essentially, this requires the development of housing that is optimal in terms of size, stability, and comfort.
In light of this, Yakolev presents what he considers to be the most likely prospects for humanity’s exit to space between now and 2030. This will include the creation of the first space biospheres with artificial gravity, which will lead to key developments in terms of materials technology, life support-systems, and the robotic systems and infrastructure needed to install and service habitats in Low Earth Orbit (LEO).
Artist’s depiction of a pair of O’Neill cylinders. Credit: Rick Guidice/NASA Ames Research Center
These habitats could be serviced thanks to the creation of robotic spacecraft that could harvest resources from nearby bodies – such as the Moon and Near-Earth Objects (NEOs). This concept would not only remove the need for planetary protections – i.e. worries about contaminating Mars’ biosphere (assuming the presence of bacterial life), it would also allow human beings to become accustomed to space more gradually.
As Yakovlev told Universe Today via email, the advantages to space habitats can be broken down into four points:
“1. This is a universal way of mastering the infinite spaces of the Cosmos, both in the Solar System and outside it. We do not need surfaces for installing houses, but resources that robots will deliver from planets and satellites. 2. The possibility of creating a habitat as close as possible to the earth’s cradle allows one to escape from the inevitable physical degradation under a different gravity. It is easier to create a protective magnetic field.
“3. The transfer between worlds and sources of resources will not be a dangerous expedition, but a normal life. Is it good for sailors without their families? 4. The probability of death or degradation of mankind as a result of the global catastrophe is significantly reduced, as the colonization of the planets includes reconnaissance, delivery of goods, shuttle transport of people – and this is much longer than the construction of the biosphere in the Moon’s orbit. Dr. Stephen William Hawking is right, a person does not have much time.”
And with space habitats in place, some very crucial research could begin, including medical and biologic research which would involve the first children born in space. It would also facilitate the development of reliable space shuttles and resource extraction technologies, which will come in handy for the settlement of other bodies – like the Moon, Mars, and even exoplanets.
Ultimately, Yakolev thinks that space biospheres could also be accomplished within a reasonable timeframe – i.e. between 2030 and 2050 – which is simply not possible with terraforming. Citing the growing presence and power of the commercial space sector, Yakolev also believed a lot of the infrastructure that is necessary is already in place (or under development).
“After we overcome the inertia of thinking +20 years, the experimental biosphere (like the settlement in Antarctica with watches), in 50 years the first generation of children born in the Cosmos will grow and the Earth will decrease, because it will enter the legends as a whole… As a result, terraforming will be canceled. And the subsequent conference will open the way for real exploration of the Cosmos. I’m proud to be on the same planet as Elon Reeve Musk. His missiles will be useful to lift designs for the first biosphere from the lunar factories. This is a close and direct way to conquer the Cosmos.”
With NASA scientists and entrepreneurs like Elon Musk and Bas Landorp looking to colonize Mars in the near future, and other commercial aerospace companies developing LEO, the size and shape of humanity’s future in space is difficult to predict. Perhaps we will jointly decide on a path that takes us to the Moon, Mars, and beyond. Perhaps we will see our best efforts directed into near-Earth space.
Or perhaps we will see ourselves going off in multiple directions at once. Whereas some groups will advocate creating space habitats in LEO (and later, elsewhere in the Solar System) that rely on artificial gravity and robotic spaceships mining asteroids for materials, others will focus on establishing outposts on planetary bodies, with the goal of turning them into “new Earths”.
Between them, we can expect that humans will begin developing a degree of “space expertise” in this century, which will certainly come in handy when we start pushing the boundaries of exploration and colonization even further!
A full-scale model of the JWST went on a bit of a World Tour. Here it is in Munich, Germany. Image Credit: EADS Astrium
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 6 of the world’s Super Telescopes:
The James Webb Space Telescope“>James Webb Space Telescope (JWST, or the Webb) may be the most eagerly anticipated of the Super Telescopes. Maybe because it has endured a tortured path on its way to being built. Or maybe because it’s different than the other Super Telescopes, what with it being 1.5 million km (1 million miles) away from Earth once it’s operating.
The JWST will do its observing while in what’s called a halo orbit at L2, a sort of gravitationally neutral point 1.5 million km from Earth. Image: NASA/JWST
If you’ve been following the drama behind the Webb, you’ll know that cost overruns almost caused it to be cancelled. That would’ve been a real shame.
The JWST has been brewing since 1996, but has suffered some bumps along the road. That road and its bumps have been discussed elsewhere, so what follows is a brief rundown.
Initial estimates for the JWST were a $1.6 billion price tag and a launch date of 2011. But the costs ballooned, and there were other problems. This caused the House of Representatives in the US to move to cancel the project in 2011. However, later that same year, US Congress reversed the cancellation. Eventually, the final cost of the Webb came to $8.8 billion, with a launch date set for October, 2018. That means the JWST’s first light will be much sooner than the other Super Telescopes.
The business end of the James Webb Space Telescope is its 18-segment primary mirror. The gleaming, gold-coated beryllium mirror has a collecting area of 25 square meters. Image: NASA/Chris Gunn
The Webb was envisioned as a successor to the Hubble Space Telescope, which has been in operation since 1990. But the Hubble is in Low Earth Orbit, and has a primary mirror of 2.4 meters. The JWST will be located in orbit at the LaGrange 2 point, and its primary mirror will be 6.5 meters. The Hubble observes in the near ultraviolet, visible, and near infrared spectra, while the Webb will observe in long-wavelength (orange-red) visible light, through near-infrared to the mid-infrared. This has some important implications for the science yielded by the Webb.
The Webb’s Instruments
The James Webb is built around four instruments:
The Near-Infrared Camera (NIRCam)
The Near-Infrared Spectrograph (NIRSpec)
The Mid-Infrared Instrument(MIRI)
The Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS)
This image shows the wavelengths of the infrared spectrum that Webb’s instruments can observe. Image: NASA/JWST
The NIRCam is Webb’s primary imager. It will observe the formation of the earliest stars and galaxies, the population of stars in nearby galaxies, Kuiper Belt Objects, and young stars in the Milky Way. NIRCam is equipped with coronagraphs, which block out the light from bright objects in order to observe dimmer objects nearby.
NIRSpec will operate in a range from 0 to 5 microns. Its spectrograph will split the light into a spectrum. The resulting spectrum tells us about an objects, temperature, mass, and chemical composition. NIRSpec will observe 100 objects at once.
MIRI is a camera and a spectrograph. It will see the redshifted light of distant galaxies, newly forming stars, objects in the Kuiper Belt, and faint comets. MIRI’s camera will provide wide-field, broadband imaging that will rank up there with the astonishing images that Hubble has given us a steady diet of. The spectrograph will provide physical details of the distant objects it will observe.
The Fine Guidance Sensor part of FGS/NIRISS will give the Webb the precision required to yield high-quality images. NIRISS is a specialized instrument operating in three modes. It will investigate first light detection, exoplanet detection and characterization, and exoplanet transit spectroscopy.
The Science
The over-arching goal of the JWST, along with many other telescopes, is to understand the Universe and our origins. The Webb will investigate four broad themes:
First Light and Re-ionization: In the early stages of the Universe, there was no light. The Universe was opaque. Eventually, as it cooled, photons were able to travel more freely. Then, probably hundreds of millions of years after the Big Bang, the first light sources formed: stars. But we don’t know when, or what types of stars.
How Galaxies Assemble: We’re accustomed to seeing stunning images of the grand spiral galaxies that exist in the Universe today. But galaxies weren’t always like that. Early galaxies were often small and clumpy. How did they form into the shapes we see today?
The Birth of Stars and Protoplanetary Systems: The Webb’s keen eye will peer straight through clouds of dust that ‘scopes like the Hubble can’t see through. Those clouds of dust are where stars are forming, and their protoplanetary systems. What we see there will tell us a lot about the formation of our own Solar System, as well as shedding light on many other questions.
Planets and the Origins of Life: We now know that exoplanets are common. We’ve found thousands of them orbiting all types of stars. But we still know very little about them, like how common atmospheres are, and if the building blocks of life are common.
These are all obviously fascinating topics. But in our current times, one of them stands out among the others: Planets and the Origins of Life.
The recent discovery the TRAPPIST 1 system has people excited about possibly discovering life in another solar system. TRAPPIST 1 has 7 terrestrial planets, and 3 of them are in the habitable zone. It was huge news in February 2017. The buzz is still palpable, and people are eagerly awaiting more news about the system. That’s where the JWST comes in.
One big question around the TRAPPIST system is “Do the planets have atmospheres?” The Webb can help us answer this.
The NIRSpec instrument on JWST will be able to detect any atmospheres around the planets. Maybe more importantly, it will be able to investigate the atmospheres, and tell us about their composition. We will know if the atmospheres, if they exist, contain greenhouse gases. The Webb may also detect chemicals like ozone and methane, which are biosignatures and can tell us if life might be present on those planets.
You could say that if the James Webb were able to detect atmospheres on the TRAPPIST 1 planets, and confirm the existence of biosignature chemicals there, it will have done its job already. Even if it stopped working after that. That’s probably far-fetched. But still, the possibility is there.
Launch and Deployment
The science that the JWST will provide is extremely intriguing. But we’re not there yet. There’s still the matter of JWST’s launch, and it’s tricky deployment.
The JWST’s primary mirror is much larger than the Hubble’s. It’s 6.5 meters in diameter, versus 2.4 meters for the Hubble. The Hubble was no problem launching, despite being as large as a school bus. It was placed inside a space shuttle, and deployed by the Canadarm in low earth orbit. That won’t work for the James Webb.
This image shows the Hubble Space Telescope being held above the shuttle’s cargo bay by the Canadian-built Remote Manipulator System (RMS) arm, or Canadarm. A complex operation, but not as complex as JWST’s deployment. Image: NASA
The Webb has to be launched aboard a rocket to be sent on its way to L2, it’s eventual home. And in order to be launched aboard its rocket, it has to fit into a cargo space in the rocket’s nose. That means it has to be folded up.
The mirror, which is made up of 18 segments, is folded into three inside the rocket, and unfolded on its way to L2. The antennae and the solar cells also need to unfold.
Unlike the Hubble, the Webb needs to be kept extremely cool to do its work. It has a cryo-cooler to help with that, but it also has an enormous sunshade. This sunshade is five layers, and very large.
We need all of these components to deploy for the Webb to do its thing. And nothing like this has been tried before.
The Webb’s launch is only 7 months away. That’s really close, considering the project almost got cancelled. There’s a cornucopia of science to be done once it’s working.
But we’re not there yet, and we’ll have to go through the nerve-wracking launch and deployment before we can really get excited.
Ask me my favorite object in the Solar System, especially to see through a telescope, and my answer is always the same: Saturn.
Saturn is this crazy, ringed world, different than any other place we’ve ever seen. And in a small telescope, you can really see the ball of the planet, you can see its rings. It’s one thing to see a world like this from afar, a tiny jumping image in a telescope. To really appreciate and understand a place like Saturn, you’ve got to visit.
And thanks to NASA’s Cassini spacecraft, that’s just what we’ve been doing for the last 13 years. Take a good close look at this amazing ringed planet and its moons, and studying it from every angle.
Cassini orbiting Saturn. Credit: NASA
Throughout this article, I’m going to regale you with the amazing discoveries made by Cassini at Saturn. What it taught us, and what new mysteries it uncovered.
NASA’s Cassini spacecraft was launched from Earth on October 15, 1997. Instead of taking the direct route, it made multiple flybys of Venus, a flyby of Earth and a flyby of Jupiter. Each one of these close encounters boosted Cassini’s velocity, allowing it to make the journey with less escape velocity from Earth.
It arrived at Saturn on July 1st, 2004 and began its science operations shortly after that. The primary mission lasted 4 years, and then NASA extended its mission two more times. The first ending in 2010, and the second due to end in 2017. But more on that later.
Before Cassini, we only had flybys of Saturn. NASA’s Pioneer 11, and Voyagers 1 and 2 both zipped past the planet and its moons, snapping pictures as they went.
But Cassini was here to stay. To orbit around and around the planet, taking photos, measuring magnetic fields, and studying chemicals.
For Saturn itself, Cassini was able to make regular observations of the planet as it passed through entire seasons. This allowed it to watch how the weather and atmospheric patterns changed over time. The spacecraft watched lightning storms dance through the cloudtops at night.
This series of images from NASA’s Cassini spacecraft shows the development of the largest storm seen on the planet since 1990. These true-color and composite near-true-color views chronicle the storm from its start in late 2010 through mid-2011, showing how the distinct head of the storm quickly grew large but eventually became engulfed by the storm’s tail. Credit: NASA/JPL-Caltech/Space Science Institute
Two highlights. In 2010, Cassini watched a huge storm erupt in the planet’s northern hemisphere. This storm dug deep into Saturn’s lower atmosphere, dredging up ice from a layer 160 kilometers below and mixing it onto the surface. This was the first time that astronomers were able to directly study this water ice on Saturn, which is normally in a layer hidden from view.
Natural color images taken by NASA’s Cassini wide-angle camera, showing the changing appearance of Saturn’s north polar region between 2012 and 2016.. Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University
The second highlight, of course, is the massive hexagonal storm churning away in Saturn’s northern pole. This storm was originally seen by Voyager, but Cassini brought its infrared and visible wavelength instruments to bear.
Why a hexagon? That’s still a little unclear, but it seems like when you rotate fluids of different speeds, you get multi-sided structures like this.
Cassini showed how the hexagonal storm has changed in color as Saturn moved through its seasons.
This is one of my favorite images sent back by Cassini. It’s the polar vortex at the heart of the hexagon. Just look at those swirling clouds.
The polar vortex, in all its glory. Credit: NASA/JPL-Caltech/Space Science Institute
Now, images of Saturn itself are great and all, but there was so much else for Cassini to discover in the region.
Cassini studied Saturn’s rings in great detail, confirming that they’re made up of ice particles, ranging in size as small a piece of dust to as large as a mountain. But the rings themselves are actually quite thin. Just 10 meters thick in some places. Not 10 kilometers, not 10 million kilometers, 10 meters, 30 feet.
The spacecraft helped scientists uncover the source of Saturn’s E-ring, which is made up of fresh icy particles blasting out of its moon Enceladus. More on that in a second too.
Vertical structures, among the tallest seen in Saturn’s main rings, rise abruptly from the edge of Saturn’s B ring to cast long shadows on the ring in this image taken by NASA’s Cassini spacecraft two weeks before the planet’s August 2009 equinox. Credit: NASA/JPL/Space Science Institute
Here’s another one of my favorite images of the mission. You’re looking at strange structures in Saturn’s B-ring. Towering pillars of ring material that rise 3.5 kilometers above the surrounding area and cast long shadows. What is going on here?
They’re waves, generated in the rings and enhanced by nearby moons. They move and change over time in ways we’ve never been able to study anywhere else in the Solar System.
Daphnis, one of Saturn’s ring-embedded moons, is featured in this view, kicking up waves as it orbits within the Keeler gap. Credit: NASA/JPL-Caltech/Space Science Institute
Cassini has showed us that Saturn’s rings are a much more dynamic place than we ever thought. Some moons are creating rings, other moons are absorbing or distorting them. The rings generate bizarre spoke patterns larger than Earth that come and go because of electrostatic charges.
Speaking of moons, I’m getting to the best part. What did Cassini find at Saturn’s moons?
Let’s start with Titan, Saturn’s largest moon. Before Cassini, we only had a few low resolution images of this fascinating world. We knew Titan had a dense atmosphere, filled with nitrogen, but little else.
Cassini was carrying a special payload to assist with its exploration of Titan: the Huygens lander. This tiny probe detached from Cassini just before its arrival at Saturn, and parachuted through the cloudtops on January 14, 2005, analyzing all the way. Huygens returned images of its descent through the atmosphere, and even images of the freezing surface of Titan.
Huygen’s view of Titan. Credit: ESA/NASA/JPL/University of Arizona
But Cassini’s own observations of Titan took the story even further. Instead of a cold, dead world, Cassini showed that it has active weather, as well as lakes, oceans and rivers of hydrocarbons. It has shifting dunes of pulverized rock hard water ice.
If there’s one place that needs exploring even further, it’s Titan. We should return with sailboats, submarines and rovers to better explore this amazing place.
A view of Mimas from the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
We learned, without a shadow of a doubt, that Mimas absolutely looks like the Death Star. No question. But instead of a megalaser, this moon has a crater a third of its own size.
Saturn’s moon Iapetus. Image credit: NASA/JPL/SSI
Cassini helped scientists understand why Saturn’s moon Iapetus has one light side and one dark side. The moon is tidally locked to Saturn, its dark side always leading the moon in orbit. It’s collecting debris from another Saturnian moon, Phoebe, like bugs hitting the windshield of a car.
Perhaps the most exciting discovery that Cassini made during its mission is the strange behavior of Saturn’s moon Enceladus. The spacecraft discovered that there are jets of water ice blasting out of the moon’s southern pole. An ocean of liquid water, heated up by tidal interactions with Saturn, is spewing out into space.
And as you know, wherever we find water on Earth, we find life. We thought that water in the icy outer Solar System would be hard to reach, but here it is, right at the surface, venting into space, and waiting for us to come back and investigate it further.
Icy water vapor geysers erupting from fissures on Enceladus. Credit: NASA/JPL
On September 15, 2017, the Cassini mission will end. How do we know it’s going to happen on this exact date? Because NASA is going to crash the spacecraft into Saturn, killing it dead.
That seems a little harsh, doesn’t it, especially for a spacecraft which has delivered so many amazing images to us over nearly two decades of space exploration? And as we’ve seen from NASA’s Opportunity rover, still going, 13 years longer than anticipated. Or the Voyagers, out in the depths of the void, helping us explore the boundary between the Solar System and interstellar space. These things are built to last.
The problem is that the Saturnian system contains some of the best environments for life in the Solar System. Saturn’s moon Enceladus, for example, has geysers of water blasting out into space.
Cassini spacecraft is covered in Earth-based bacteria and other microscopic organisms that hitched a ride to Saturn, and would be glad to take a nice hot Enceladian bath. All they need is liquid water and a few organic chemicals to get going, and Enceladus seems to have both.
NASA feels that it’s safer to end Cassini now, when they can still control it, than to wait until they lose communication or run out of propellant in the future. The chances that Cassini will actually crash into an icy moon and infect it with our Earth life are remote, but why take the risk?
For the last few months, Cassini has been taking a series of orbits to prepare itself for its final mission. Starting in April, it’ll actually cross inside the orbit of the rings, getting closer and closer to Saturn. And on September 15th, it’ll briefly become a meteor, flashing through the upper atmosphere of Saturn, gone forever.
This graphic illustrates the Cassini spacecraft’s trajectory, or flight path, during the final two phases of its mission. The view is toward Saturn as seen from Earth. The 20 ring-grazing orbits are shown in gray; the 22 grand finale orbits are shown in blue. The final partial orbit is colored orange. Image credit: NASA/JPL-Caltech/Space Science Institute
Even in its final moments, Cassini is going to be sciencing as hard as it can. We’ll learn more about the density of consistency of the rings close to the planet. We’ll learn more about the planet’s upper atmosphere, storms and clouds with the closest possible photographs you can take.
And then it’ll all be over. The perfect finale to one of the most successful space missions in human history. A mission that revealed as many new mysteries about Saturn as it helped us answer. A mission that showed us not only a distant alien world, but our own planet in perspective in this vast Solar System. I can’t wait to go back.
How have the photos from Cassini impacted your love of astronomy? Let me know your thoughts in the comments.
Mosaic of Mercury. Credit: NASA / JHUAPL / CIW / mosaic by Jason Perry
Mercury is one of the most unusual planets in our Solar System, at least by the standards of us privileged Earthlings. Despite being the closest planet to our Sun, it is not the hottest (that honor goes to Venus). And because of its virtually non-existence atmosphere and slow rotation, temperatures on its surface range from being extremely hot to extremely cold.
Equally unusual is the diurnal cycle on Mercury – i.e. the cycle of day and night. A single year lasts only 88 days on Mercury, but thanks again to its slow rotation, a day lasts twice as long! That means that if you could stand on the surface of Mercury, it would take a staggering 176 Earth days for the Sun to rise, set and rise again to the same place in the sky just once!
Distance and Orbital Period:
Mercury is the closest planet to our Sun, but it also has the most eccentric orbit (0.2056) of any of the Solar Planets. This means that while its average distance (semi-major axis) from the Sun is 57,909,050 km (35,983,015 mi) or 0.387 AUs, this ranges considerably – from 46,001,200 km (2,8583,820 mi) at perihelion (closet) to 69,816,900 km (43,382,210 mi) at aphelion (farthest).
A timelapse of Mercury transiting across the face of the Sun. Credit: NASA
Because of this proximity, Mercury has a rapid orbital period, which varies depending on where it is in its orbit. Naturally, it moves fastest when it is at its closest to the Sun, and slowest when it is farthest. On average, its orbital velocity is 47.362 km/s (29.43 mi/s), which means it takes only 88 days to complete a single orbit of the Sun.
Astronomers used to suspect that Mercury was tidally locked to the Sun, meaning that it always showed the same face to the Sun – similar to how the Moon is tidally locked to the Earth. But radar-Doppler measurements obtained in 1965 demonstrated that Mercury is actually rotating very slowly compared to the Sun.
Sidereal vs. Solar Day:
Based on data obtained by these radar measurements, Mercury is now known to be in 3:2 orbital resonance with the Sun. This means that the planet completes three rotations on its axis for every two orbits it makes around the Sun. At it’s current rotational velocity – 3.026 m/s, or 10.892 km/h (6.77 mph) – it takes Mercury 58.646 days to complete a single rotation on its axis.
While this might lead some to conclude that a single day on Mercury is about 58 Earth days – thus making the length of a day and year correspond to the same 3:2 ratio – this would be inaccurate. Due to its rapid orbital velocity and slow sidereal rotation, a Solar Day on Mercury (the time it takes for the Sun to return to the same place in the sky) is actually 176 days.
In that respect, the ratio of days to years on Mercury is actually 1:2. The only places that are exempt to this day and night cycle are the polar regions. The cratered northern polar region, for example, exists in a state of perpetual shadow. Temperatures in these craters are also cool enough that significant concentrations of water ice can exist in stable form.
For over 20 years, scientists believed that radar-bright images from Mercury’s northern polar regions might indicate the presence of water ice there. In November of 2012, NASA’s MESSENGER probe examined the northern polar region using its neutron spectrometer and laser altimeter and confirmed the presence of both water ice and organic molecules.
View of Mercury’s north pole. based on MESSENGER probe data, showing polar deposits of water ice. Credit: NASA/JHUAPL/Carnegie Institute of Science/NAIC/Arecibo Observatory
Yes, as if Mercury weren’t strange enough, it turns out that a single day on Mercury lasts as long as two years! Just another oddity for a planet that likes to keep things really hot, really cold, and is really eccentric.
ASA's Cassini spacecraft looks toward the night side of Saturn's largest moon and sees sunlight scattering through the periphery of Titan's atmosphere and forming a ring of color.
Credit: NASA/JPL-Caltech/Space Science Institute
Last week – from Monday, February 27th to Wednesday, March 1st – NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. In the course of the many presentations, speeches and panel discussions, NASA’s shared its many plans for the future of space exploration with the international community.
Among the more ambitious of these was a proposal to explore Titan using an aerial explorer and a lander. Building upon the success of the ESA’s Cassini-Huygen mission, this plan would involve a balloon that would explore Titan’s surface from low altitude, along with a Mars Pathfinder-style mission that would explore the surface.
Ultimately, the goal a mission to Titan would be to explore the rich organic chemical environment the moon has, which presents a unique opportunity for planetary researchers. For some time, scientists have understood that Titan’s surface and atmosphere have an abundance of organic compounds and all the prebiotic chemistry necessary for life to function.
Artist depiction of Huygens landing on Titan. Credit: ESA
“Titan’s of particular interest because the abundant and complex organic chemistry can teach us about chemical interactions that could have occurred here on Earth (and elsewhere?) leading to the development of life. Furthermore, not only does Titan have an interior liquid-water ocean, but there will also have been opportunities for organic material to have mixed with liquid water at Titan’s surface, for example impact craters and possibly cryovolcanic eruptions. The combination of organic material with liquid water, of course, increases astrobiological potential.”
For this reason, the exploration of Titan has been a scientific goal for decades. The only question is how best to go about exploring Titan’s unique environment. During previous Decadal Surveys – such as the Campaign Strategy Working Group (CSWG) on Prebiotic Chemistry in the Outer Solar System, of which Lorenz was a contributor – has suggested that a mobile aerial vehicle (such as an airship or a balloon) would well-suited to the task.
However, such vehicles would be unable to study Titan’s methane lakes, which are one of the most exciting draws of the moon as far as research into prebiotic chemistry goes. What’s more, an aerial vehicle would not be able to conduct in-situ chemical analysis of the surface, much like what the Mars Exploration Rovers (Spirit, Opportunity and Curiosity) have been doing on Mars – and with immense results!
The ESA’s TALISE (Titan Lake In-situ Sampling Propelled Explorer) on the left, and NASA’s Titan Mare Explorer (TiME) on the right. Credit: bisbos.com
At the same time, Lorenz and his colleagues examined concepts for the exploration of Titan’s hydrocarbon seas – like the proposed Titan Mare Explorer (TiME) capsule. As one of several finalists of NASA’s 2010 Discovery competition, this concept called for the deployment of nautical robot to Titan in the coming decades, where it would study its methane lakes to learn more about the methane cycle and search for signs of organic life.
While such a proposal would be cost-effective and presents some very exciting opportunities for research, it also has some limitations. For instance, during the 2020s-2030s, Titan’s northern hemisphere will be experiencing its winter season; at which point the thickness of its atmosphere will make direct-to-Earth communications and Earth views impossible. On top of that, a nautical vehicle would preclude the exploration of Titan’s land surfaces.
These offer some of the most likely prospects for studying Titan’s advanced chemical evolution, including Titan’s dune sands. As a windswept region, this area likely has material deposited from all over Titan and may also contain aqueously altered materials. Much as the Mars Pathfinder landing site was selected so it could collect samples from a wide area, such as location would be an ideal site for a lander.
As such, Lorenz and his colleagues advocated the type of mission that was articulated in the 2007 Flagship Study, which called for a Montgolfière balloon for regional exploration and a Pathfinder-like lander. This would provide the opportunity to conduct surface imaging at resolutions that are impossible from orbit (due to the thick atmosphere) as well as investigating the surface chemistry and interior structure of the moon.
Artist’s conception of a possible structure for underground liquid reservoirs on Saturn moon’s Titan. Credit: ESA/ATG medialab
So while the balloon would gather high-resolution geographical data of the moon, the lander could conduct seismological surveys that would characterize the thickness of the ice above Titan’s internal water ocean. However, a lander mission would be limited in terms of range, and the surface of Titan presents problems for mobility. This would make multiple landers, or a relocatable lander, the most desired option.
“Potential targets include areas where we can measure solid surface materials, the composition of which is still not well known, Titan’s dune sands, for example,” said Turtle. “Detailed in situ analysis is required to determine their composition. The lakes and seas are also intriguing; however, in the nearer term (missions arriving in the 2030s) most of those will be in winter darkness. So, exploring them would likely have to wait until the 2040s.”
This mission concept would also take advantage of several technological advances that have been made in recent years. As Lorenz explained in the course of the presentation:
“Heavier-than-air mobility at Titan is in fact highly efficient, moreover, improvements in autonomous aircraft in the two decades since the CSWG make such exploration a realistic prospect. Multiple in-situ landers delivered by an aerial vehicle like an airplane or a lander with aerial mobility to access multiple sites, would provide the most desirable scientific capability, highly relevant to the themes of origins, workings, and life.”
Updated maps of Titan, based on the Cassini imaging science subsystem. Credit: NASA/JPL/Space Science Institute
However, addressing some additional challenges not raised at the 2050 Vision Workshop, they will be presenting a slight twist on their idea. Instead of a balloon and multiple landers, they will present a mission concept involving a “Dragonfly” qaudcopter. This four-rotor vehicle would be able to take advantage of Titan’s thick atmosphere and low gravity to obtain samples and determine the surface composition in multiple geological settings.
This concept also incorporates a lot of recent advances in technology, which include modern control electronics and advances in commerical unmanned aerial vehicle (UAV) designs. On top of that, a quadcopter would do away with chemically-powered retrorockets and could power-up between flights, giving it a potentially much longer lifespan.
These and other concepts for exploring Saturn’s moon Titan are sure to gain traction in the coming years. Given the many mysteries locked away on this world – with includes abundant water ice, prebiotic chemistry, a methane cycle, and a subsurface ocean that is likely to be a prebiotic environment – it is certainly a popular target for scientific research.
An artist's illustration of the Thirty Meter Telescope at its preferred location at Mauna Kea, Hawaii. Image Courtesy TMT International Observatory
As Carl Sagan said, “Understanding is Ecstasy.” But in order 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 six Super Telescopes being built:
The Thirty Meter Telescope (TMT) is being built by an international group of countries and institutions, like a lot of Super Telescopes are. In fact, they’re proud of pointing out that the international consortium behind the TMT represents almost half of the world’s population; China, India, the USA, Japan, and Canada. The project needs that many partners to absorb the cost; an estimated $1.5 billion.
The heart of any of the world’s Super Telescopes is the primary mirror, and the TMT is no different. The primary mirror for the TMT is, obviously, 30 meters in diameter. It’s a segmented design consisting of 492 smaller mirrors, each one a 1.4 meter hexagon.
The light collecting capability of the TMT will be 10 times that of the Keck Telescope, and more than 144 times that of the Hubble Space Telescope.
But the TMT is more than just an enormous ‘light bucket.’ It also excels with other capabilities that define a super telescope’s effectiveness. One of those is what’s called diffraction-limited spatial resolution (DLSR).
An illustration of the segmented primary mirror of the Thirty Meter Telescope. Image Courtesy TMT International Observatory
When a telescope is pointed at distant objects that appear close together, the light from both can scatter enough to make the two objects appear as one. Diffraction-limited spatial resolution means that when a ‘scope is observing a star or other object, none of the light from that object is scattered by defects in the telescope. The TMT will more easily distinguish objects that are close to each other. When it comes to DLSR, the TMT will exceed the Keck by a factor of 3, and will exceed the Hubble by a factor of 10 at some wavelengths.
Crucial to the function of large, segmented mirrors like the TMT is active optics. By controlling the shape and position of each segment, active optics allows the primary mirror to compensate for changes in wind, temperature, or mechanical stress on the telescope. Without active optics, and its sister technology adaptive optics, which compensates for atmospheric disturbance, any telescope larger than about 8 meters would not function properly.
The TMT will operate in the near-ultraviolet, visible, and near-infrared wavelengths. It will be smaller than the European Extremely Large Telescope (E-ELT), which will have a 39 meter primary mirror. The E-ELT will operate in the optical and infrared wavelengths.
The world’s Super Telescopes are behemoths. Not just in the size of their mirrors, but in their mass. The TMT’s moving mass will be about 1,420 tonnes. Moving the TMT quickly is part of the design of the TMT, because it must respond quickly when something like a supernova is spotted. The detailed science case calls for the TMT to acquire a new target within 5 to 10 minutes.
This requires a complex computer system to coordinate the science instruments, the mirrors, the active optics, and the adaptive optics. This was one of the initial challenges of the TMT project. It will allow the TMT to respond to transient phenomena like supernovae when spotted by other telescopes like the Large Synoptic Survey Telescope.
The Science
The TMT will investigate most of the important questions in astronomy and cosmology today. Here’s an overview of major topics that the TMT will address:
The Nature of Dark Matter
The Physics of Extreme Objects like Neutron Stars
Early galaxies and Cosmic Reionization
Galaxy Formation
Super-Massive Black Holes
Exploration of the Milky Way and Nearby Galaxies
The Birth and Early Lives of Stars and Planets
Time Domain Science: Supernovae and Gamma Ray Bursts
Exo-planets
Our Solar System
This is a comprehensive list of topics, to be sure. It leaves very little out, and is a testament to the power and effectiveness of the TMT.
The raw power of the TMT is not in question. Once in operation it will advance our understanding of the Universe on multiple fronts. But the actual location of the TMT could still be in question.
The top of Mauna Kea is a prime site for telescopes, as shown in this image. Image Courtesy Mauna Kea Observatories
The dispute between some of the Hawaiian people and the TMT has been well-documented elsewhere, but the basic complaint about the TMT is that the top of Mauna Kea is sacred land, and they would like the TMT to be built elsewhere.
The organizations behind the TMT would still like it to be built at Mauna Kea, and a legal process is unfolding around the dispute. During that process, they identified several possible alternate sites for the telescope, including La Palma in the Canary Islands. Universe Today contacted TMT Observatory Scientist Christophe Dumas, PhD., about the possible relocation of the TMT to another site.
Dr. Dumas told us that “Mauna Kea remains the preferred location for the TMT because of its superb observing conditions, and because of the synergy with other TMT partner facilities already present on the mountain. Its very high elevation of almost 14,000 feet makes it the premier astronomical site in the northern hemisphere. The sky above Mauna Kea is very stable, which allows very sharp images to be obtained. It has also excellent transparency, low light pollution and stable cold temperatures that improves sensitivity for observations in the infrared.”
The preferred secondary site at La Palma is home to over 10 other telescopes, but would relocation to the Canary Islands affect the science done by the TMT? Dr. Dumas says that the Canary Islands site is excellent as well, with similar atmospheric characteristics to Mauna Kea, including stability, transparency, darkness, and fraction of clear-nights.
The Gran Telescopio Canarias (Great Canary Telescope) is the largest ‘scope currently at La Palma. At 10m diameter, it would be dwarfed by the TMT. Image: By Pachango – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6880933
As Dr. Dumas explains, “La Palma is at a lower elevation site and on average warmer than Mauna Kea. These two factors will reduce TMT sensitivity at some wavelengths in the infrared region of the spectrum.”
Dr. Dumas told Universe Today that this reduced sensitivity in the infrared can be overcome somewhat by scheduling different observing tasks. “This specific issue can be partly mitigated by implementing an adaptive scheduling of TMT observations, to match the execution of the most demanding infrared programs with the best atmospheric conditions above La Palma.”
Court Proceedings End
On March 3rd, 44 days of court hearings into the TMT wrapped up. In that time, 71 people testified for and against the TMT being constructed on Mauna Kea. Those against the telescope say that the site is sacred land and shouldn’t have any more telescope construction on it. Those for the TMT spoke in favor of the science that the TMT will deliver to everyone, and the education opportunities it will provide to Hawaiians.
Though construction has been delayed, and people have gone to court to have the project stopped, it seems like the TMT will definitely be built—somewhere. The funding is in place, the design is finalized, and manufacturing of the components is underway. The delays mean that the TMT’s first light is still uncertain, but once we get there, the TMT will be another game-changer, just like the world’s other Super Telescopes.
Perspective view looking from an unnamed crater (bottom right) towards the Worcester Crater. The region sits at the mouth of Kasei Valles, where fierce floodwaters emptied into Chryse Planitia. Credit: ESA/DLR/FU Berlin
The Mars Express probe was the European Space Agency’s first attempt to explore Mars. Since its arrival around the Red Planet in 2003, the probe has helped determine the composition of the atmosphere, map the mineral composition of the surface, studied the interaction between the atmosphere and solar wind, and taken many high-resolution images of the surface.
And even after 14 years of continuous operation, it is still revealing interesting things about Mars and its past. The latest find comes from the Kasei Valles region, where the probe captured new images of the giant system of canyons. As one of the largest outflow channel networks on the Red Planet, this region is evidence of a massive flood having taken place billions of years ago.
This region formed between 3.6 and 3.4 billion years ago, when a combination of volcanic and tectonic activity in the Tharsis region triggered groundwater releases from Echus Chasma. This chasm, located in the Lunae Planum plateau, contains clay deposits that indicate the presence of liquid water at one time. This water then flooded through Kasei Valles, emptying into the Chryse Planitia region and leaving behind signs of water erosion.
Colour-coded topographic view of the mouth of Kasei Valles, showing the Worcester Crater. Credit: ESA/DLR/FU Berlin.
The Mars Express probe has captured images of this region before. But these latest images, which were snapped n May 25th, 2016, captured the topography of an area that lies at the mouth of the system. Of particular interest was the 25-km-wide Worcester Crater, the remains of an impact that has managed to remain intact despite the erosive force of the mega-flood.
The appearance of this crater and the features around it – which resemble an island – tell us much about the region and its history. For instance, the island has a stepped topography, which is likely the result of its interaction with the flood waters. After the impact threw up material around the crater, moving water pushed it downstream, creating a rigid wall facing towards Kasei Valles and a sloping wall trailing away from it.
The topography of the island is also suggestive of variations in water levels, or possibly different flood episodes. As the water rose and fell, or multiple streams formed over time, the downstream portion of the “island” was affected. There is also the larger crater that appears to the upper right of the image, which sits in a plateau 1 km (0.6 mi) higher than the plains below.
There is a small depression in its center, which would imply that a weaker layer – possibly made of ice – existed under the plateau during the time of impact. This is consistent with the patterns noted in Worcester’s debris blanket, which also suggest the area was rich in water or water-ice during the flooding. The presence of small branch-like channels (aka. dendritic channels) around the plateau are another indication that water levels here varied over time.
Context image shows a region of Mars where Kasei Valles empties into the vast Chryse Planitia. Credit: NASA/MGS/MOLA Science Team
Many smaller craters are also visible in this photo across the mouth of the Kasei Valles region, which also appear to have “tails” of ejected material. This is also true of the crater that sits adjacent to Worchester, who’s debris blanket appears to be largely intact. This would suggest that these craters were formed after the flooding, and any tails that formed were the result of wind.
From all this, it can be concluded that roughly three and a half billion years ago, the mouth of the Kasei Valles region still had water on its surface – possibly still in liquid form but most likely in the form of ice. Volcanic activity – which Mars was still experiencing at the time – then triggered the release of flood waters, which created debris and erosion features throughout the region.
As a result, this latest image manages to capture a preserved record of the geological activity in this region, one which goes back billions of years. And in addition to proving that Mars still had water on its surface, it also confirms that Mars was still experiencing volcanism. It is because of ongoing discoveries like these that the Mars Express mission has been extended several times, the most recent of which extended the mission to end of 2018.
