Artist's rendition of the Dawn mission on approach to the protoplanet Ceres. Credit: NASA/JPL
The Dawn probe continues to excite and amaze! Since it achieved orbit around Ceres in March of 2015, it has been sending back an impressive stream of data and images on the protoplanet. In addition to capturing pictures of the mysterious “bright spots” on Ceres’ surface, it has also revealed evidence of cryovolcanism and the possibility of an interior ocean that could even support life.
Most recently, the Dawn probe conducted observations of the protoplanet while it was at opposition – directly between the Sun and Ceres surface – on April 29th. From this position, the craft was able to capture pictures of the Occator Crater, which contains the brightest spot on Ceres. These images were then stitched together by members of the mission team in order to create a short movie that showcases the view Dawn had of the planet.
The images were snapped when the Dawn probe was at an altitude of about 20,000 km (12,000 mi) from Ceres’ surface. As you can see (by clicking on the image below), the short movie shows the protoplanet rotating so that the Occator Crater is featured prominently. This crater is unmistakable thanks to the way its bright spots (two side by side white dots) stand out from the bland, grey landscape.
NASA movie made of images taken by NASA’s Dawn spacecraft, from a position exactly between the sun and Ceres’ surface. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This increase in brightness is attributable to the size of grains of material on the surface, as well as their degree of porosity. As scientists have known for some time (thanks to the Dawn mission data) these bright spots are salt deposits, which stand out because they are more reflective than their surrounding environment. But for the sake of movie, this contrast was enhanced further in order to highlight the difference.
The observations were conducted as part of the latest phase of the Dawn mission, where it is recording cosmic rays in order to refine its earlier measurements of Ceres’ underground environment. In order to conduct these readings, the probe has been placed through an intricate set of maneuvers designed to shift its orbit around Ceres. Towards the end of April, this placed the probe in a position directly between the Sun and Ceres.
Based on previous data collected by ground-based telescopes and spacecraft that have viewed planetary bodies at opposition, the Dawn team predicted that Ceres would appear brighter from this vantage point. But rather than simply providing for some beautiful images of Ceres’ surface, the pictures are expected to reveal new details of the surface that are not discernible by visual inspection.
A view of Ceres in natural colour, pictured by the Dawn spacecraft in May 2015. Credit: NASA/JPL/Planetary Society/Justin Cowart
For more than two years now, the Dawn probe has been observing Ceres from a range of illumination angles that exceed those made of just about any other body in the Solar System. These has provided scientists with the opportunity to gain new insights into its surface features, properties, and the forces which shape it. Such observations will come in very handy as they continue to probe Ceres’ surface for hints of what lies beneath.
For years, scientists have been of the opinion that Ceres’ harbors an interior ocean that could support life. In fact, the Dawn probe has already gathered spectral data that hinted at the presence of organic molecules on the surface, which were reasoned to have been kicked up when a meteor impacted the surface. Characterizing the surface and subsurface environments will help determine if this astronomical body really could support life.
At present, the Dawn probe is maintaining an elliptical orbit that is taking it farther away from Ceres. As of May 11th, NASA reported that the probe was in good health and functioning well, despite the malfunction that took place in April where it’s third reaction wheel failed. The Dawn mission has already been extended, and it is expected to operate around Ceres until 2017.
Artist’s impression of Proxima b, which was discovered using the Radial Velocity method. Credit: ESO/M. Kornmesser
The extra-solar planet known as Proxima b has occupied a special place in the public mind ever since its existence was announced in August of 2016. As the closest exoplanet to our Solar System, its discovery has raised questions about the possibility of exploring it in the not-too-distant future. And even more tantalizing are the questions relating to its potential habitability.
Despite numerous studies that have attempted to indicate whether the planet could be suitable for life as we know it, nothing definitive has been produced. Fortunately, a team of astrophysics from the University of Exeter – with the help of meteorology experts from the UK’s Met Office – have taken the first tentative steps towards determining if Proxima b has a habitable climate.
According to their study, which appeared recently in the journal Astronomy & Astrophysics, the team conducted a series of simulations using the state-of-the-art Met Office Unified Model (UM). This numerical model has been used for decades to study Earth’s atmosphere, with applications ranging from weather prediction to the effects of climate change.
Artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. The double star Alpha Centauri AB is visible to the upper right of Proxima itself. Credit: ESO
With this model, the team simulated what the climate of Proxima b would be like if it had a similar atmospheric composition to Earth. They also conducted simulations on what the planet would be like it if had a much simpler atmosphere – one composed of nitrogen with trace amounts of carbon dioxide. Last, but not least, they made allowances for variations in the planet’s orbit.
For instance, given the planet’s distance from its sun – 0.05 AU (7.5 million km; 4.66 million mi) – there have been questions about the planet’s orbital characteristics. On the one hand, it could be tidally-locked, where one face is constantly facing towards Proxima Centauri. On the other, the planet could be in a 3:2 orbital resonance with its sun, where it rotates three times on its axis for every two orbits (much like Mercury experiences with our Sun).
In either case, this would result in one side of the planet being exposed to quite a bit of radiation. Given the nature of M-type red dwarf stars, which are highly variable and unstable compared to other types of stars, the sun-facing side would be periodically irradiated. Also, in both orbital scenarios, the planet would be subject to significant variations in temperature that would make it difficult for liquid water to exist.
For example, on a tidally-locked planet, the main atmospheric gases on the night-facing side would be likely to freeze, which would leave the daylight zone exposed and dry. And on a planet with a 3:2 orbital resonance, a single solar day would most likely last a very long time (a solar day on Mercury lasts 176 Earth days), causing one side to become too hot and dry the other side too cold and dry.
This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Credit: ESO
By taking all this into account, the team’s simulations allowed for some crucial comparisons with previous studies, but also allowed the team to reach beyond them. As Dr. Ian Boutle, an Honorary University Fellow at the University of Exeter and the lead author of the paper, explained in a University press release:
“Our research team looked at a number of different scenarios for the planet’s likely orbital configuration using a set of simulations. As well as examining how the climate would behave if the planet was ‘tidally-locked’ (where one day is the same length as one year), we also looked at how an orbit similar to Mercury, which rotates three times on its axis for every two orbits around the sun (a 3:2 resonance), would affect the environment.”
In the end, the results were quite favorable, as the team found that Proxima b would have a remarkably stable climate with either atmosphere and in either orbital configuration. Essentially, the UM software simulations showed that when both atmospheres and both the tidally-locked and 3:2 resonance configurations were accounted for, there would still be regions on the planet where water was able to exist in liquid form.
Naturally, the 3:2 resonance example resulted in more substantial areas of the planet falling within this temperature range. They also found that an eccentric orbit, where the distance between the planet and Proxima Centauri varied to a significant degree over the course of a single orbital period, would lead to a further increase in potential habitability.
Artist’s depiction of a watery exoplanet orbiting a distant red dwarf star. New research indicates that Proxima b could be especially watery. Credit: CfA
As Dr James Manners, another Honorary University Fellow and one of the co-authors on the paper, said:
“One of the main features that distinguishes this planet from Earth is that the light from its star is mostly in the near infra-red. These frequencies of light interact much more strongly with water vapor and carbon dioxide in the atmosphere which affects the climate that emerges in our model.”
Of course, much more work needs be done before we can truly understand whether this planet is capable of supporting life as we know it. Beyond feeding the hopes of those who would like to see it colonized someday, studies into Proxima b’s conditions are also of extreme importance in determining whether or not indigenous life exists there right now.
But in the meantime, studies such as this are extremely helpful when it comes to anticipating what kinds of environments we might find on distant planets. Dr Nathan Mayne – the scientific lead on exoplanet modelling at the University of Exeter and a co-author on the paper – also indicated that climate studies of this kind could have applications for scientists here at home.
“With the project we have at Exeter we are trying to not only understand the somewhat bewildering diversity of exoplanets being discovered, but also exploit this to hopefully improve our understanding of how our own climate has and will evolve,” he said. What’s more, it helps to illustrate how conditions here on Earth can be used to predict what may exist in extra-solar environments.
While that might sound a bit Earth-centric, it is entirely reasonable to assume that planets in other star systems are subject to processes and mechanics similar to what we’ve seen on the Solar planets. And this is something we are invariably forced to do when it comes to searching for habitable planets and life beyond our Solar System. Until we can go there directly, we will be forced to measure what we don’t know by what we do.
A new study from researchers from the University of British Columbia offers a new explanation of Dark Energy. Credit: NASA
Since the late 1920s, astronomers have been aware of the fact that the Universe is in a state of expansion. Initially predicted by Einstein’s Theory of General Relativity, this realization has gone on to inform the most widely-accepted cosmological model – the Big Bang Theory. However, things became somewhat confusing during the 1990s, when improved observations showed that the Universe’s rate of expansion has been accelerating for billions of years.
This led to the theory of Dark Energy, a mysterious invisible force that is driving the expansion of the cosmos. Much like Dark Matter which explained the “missing mass”, it then became necessary to find this elusive energy, or at least provide a coherent theoretical framework for it. A new study from the University of British Columbia (UBC) seeks to do just that by postulating the Universe is expanding due to fluctuations in space and time.
The study – which was recently published in the journal Physical Review D – was led by Qingdi Wang, a PhD student with the Department of Physics and Astronomy at UBC. Under the supervisions of UBC Professor William Unruh (the man who proposed the Unruh Effect) and with assistance from Zhen Zhu (another PhD student at UBC), they provide a new take on Dark Energy.
Diagram showing the Lambda-CBR universe, from the Big Bang to the the current era. Credit: Alex Mittelmann/Coldcreation
The team began by addressing the inconsistencies arising out of the two main theories that together explain all natural phenomena in the Universe. These theories are none other than General Relativity and quantum mechanics, which effectively explain how the Universe behaves on the largest of scales (i.e. stars, galaxies, clusters) and the smallest (subatomic particles).
Unfortunately, these two theories are not consistent when it comes to a little matter known as gravity, which scientists are still unable to explain in terms of quantum mechanics. The existence of Dark Energy and the expansion of the Universe are another point of disagreement. For starters, candidates theories like vacuum energy – which is one of the most popular explanations for Dark Energy – present serious incongruities.
According to quantum mechanics, vacuum energy would have an incredibly large energy density to it. But if this is true, then General Relativity predicts that this energy would have an incredibly strong gravitational effect, one which would be powerful enough to cause the Universe to explode in size. As Prof. Unruh shared with Universe Today via email:
“The problem is that any naive calculation of the vacuum energy gives huge values. If one assumes that there is some sort of cutoff so one cannot get energy densities much greater than the Planck energy density (or about 1095 Joules/meter³) then one finds that one gets a Hubble constant – the time scale on which the Universe roughly doubles in size – of the order of 10-44 sec. So, the usual approach is to say that somehow something reduces that down so that one gets the actual expansion rate of about 10 billion years instead. But that ‘somehow’ is pretty mysterious and no one has come up with an even half convincing mechanism.”
Timeline of the Big Bang and the expansion of the Universe. Credit: NASA
Whereas other scientists have sought to modify the theories of General Relativity and quantum mechanics in order to resolve these inconsistencies, Wang and his colleagues sought a different approach. As Wang explained to Universe Today via email:
“Previous studies are either trying to modify quantum mechanics in some way to make vacuum energy small or trying to modify General Relativity in some way to make gravity numb for vacuum energy. However, quantum mechanics and General Relativity are the two most successful theories that explain how our Universe works…Instead of trying to modify quantum mechanics or General Relativity, we believe that we should first understand them better. We takes the large vacuum energy density predicted by quantum mechanics seriously and just let them gravitate according to General Relativity without modifying either of them.”
For the sake of their study, Wang and his colleagues performed new sets of calculations on vacuum energy that took its predicted high energy density into account. They then considered the possibility that on the tiniest of scales – billions of times smaller than electrons – the fabric of spacetime is subject to wild fluctuations, oscillating at every point between expansion and contraction.
Could fluctuations at the tiniest levels of space time explain Dark Energy and the expansion of the cosmos? Credit: University of Washington
As it swings back and forth, the result of these oscillations is a net effect where the Universe expands slowly, but at an accelerating rate. After performing their calculations, they noted that such an explanation was consistent with both the existence of quantum vacuum energy density and General Relativity. On top of that, it is also consistent with what scientists have been observing in our Universe for almost a century. As Unruh described it:
“Our calculations showed that one could consistently regard [that] the Universe on the tiniest scales is actually expanding and contracting at an absurdly fast rate; but that on a large scale, because of an averaging over those tiny scales, physics would not notice that ‘quantum foam’. It has a tiny residual effect in giving an effective cosmological constant (dark energy type effect). In some ways it is like waves on the ocean which travel as if the ocean were perfectly smooth but really we know that there is this incredible dance of the atoms that make up the water, and waves average over those fluctuations, and act as if the surface was smooth.”
In contrast to conflicting theories of a Universe where the various forces that govern it cannot be resolved and must cancel each other out, Wang and his colleagues presents a picture where the Universe is constantly in motion. In this scenario, the effects of vacuum energy are actually self-cancelling, and also give rise to the expansion and acceleration we have been observing all this time.
While it may be too soon to tell, this image of a Universe that is highly-dynamic (even on the tiniest scales) could revolutionize our understanding of spacetime. At the very least, these theoretical findings are sure to stimulate debate within the scientific community, as well as experiments designed to offer direct evidence. And that, as we know, is the only way we can advance our understanding of this thing known as the Universe.
Artist's representation of a Dyson ring, orbiting a star at a distance of 1 AU. Credit: WIkipedia Commons/Falcorian
During the 1960s, Freeman Dyson and Nikolai Kardashev captured the imaginations of people everywhere by making some radical proposals. Whereas Dyson proposed that intelligent species could eventually create megastructures to harness the energy of their stars, Kardashev offered a three-tiered classification system for intelligent species based on their ability to harness the energy of their planet, solar system and galaxy, respectively.
The stunning, shaped clouds of gas in the Orion Nebula make it beautiful, but also make it difficult to see inside of. This image of the Orion Nebula was captured by the Hubble Telescope. Image: NASA, ESA, M. Robberto (STScI/ESA) and
The Hubble Space Telescope Orion Treasury Project Team
Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at that Great and most brightest of nebulae – the Orion Nebula!
During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these objects is the Orion Nebula, a diffuse nebula situated just south of Orion’s Belt in the Orion constellation. Located between 1,324 and 1,364 light years distant, it is the closest massive star forming region to Earth. Little wonder then why it is the brightest nebula in the night sky and can be seen on a clear evening with the naked eye.
Description:
Known as “The Great Orion Nebula,” let’s learn what makes it glow. M42 is a great cloud of gas spanning more than 20,000 times the size of our own solar system and its light is mainly florescent. For most observers, it appears to have a slight greenish color – caused by oxygen being stripped of electrons by radiation from nearby stars.
A pair of binoculars will make the “Curlicue” pop in Orion’s Belt. Although the stars aren’t related, they form a delightfully curvy line-of-sight pattern. Credit: Bob King
At the heart of this immense region is an area known as the “Trapezium” – its four brightest stars form perhaps the most celebrated multiple star system in the night sky. The Trapezium itself belongs to a faint cluster of stars now approaching main sequence and resides in an area of the nebula known as the “Huygenian Region” (named after 17th century astronomer and optician Christian Huygens who first observed it in detail).
Buried amidst the bright ribbons and curls of this cloud of predominately hydrogen gas are many star forming regions. Appearing like “knots,” these Herbig-Haro objects are thought to be stars in the earliest stages of condensation. Associated with these objects are a great number of faint red stars and erratically luminous variables – young stars, possibly of the T Tauri type.
There are also “flare stars,” whose rapid variations in brightness mean an ever changing view. “Orion may seem very peaceful on a cold winter night, but in reality it holds very massive, luminous stars that are destroying the dusty gas cloud from which they formed,” said Tom Megeath, an astronomer at the Harvard-Smithsonian Center for Astrophysics.
While studying M42, you’ll note the apparent turbulence of the area – and with good reason. The “Great Nebula’s” many different regions move at varying speeds. The rate of expansion at the outer edges may be caused by radiation from the very youngest stars present. Said Massimo Roberto, an astronomer at the Space Science Telescope Institute in Baltimore:
“In this bowl of stars we see the entire formation history of Orion printed into the features of the nebula: arcs, blobs, pillars and rings of dust that resemble cigar smoke. Each one tells a story of stellar winds from young stars that impact the environment and the material ejected from other stars.”
The star Alnitak and Flame Nebula in Orion. Credit and copyright: César Cantú.
Although M42 may have been luminous for as long as 23,000 years, it is possible that new stars are still forming, while others were ejected by gravitation – known as “runaway” stars. A tremendous X-ray source (2U0525-06) is quite near the Trapezium and hints at the possibility of a black hole present within M42. The Trapezium’s stellar winds also are responsible for the formation of stars inside the nebula – their shock waves compressing the medium and igniting starbirth.
“When you look closely, you see that the nebula is filled with hundreds of visible shock waves,” said Bob O’Dell, an astronomer from Vanderbilt University. O’Dell was fortunate enough to use Hubble to map Orion’s stellar winds and create a map of two of Orion’s three star-forming regions… Regions where the winds have been blowing continuously for nearly 1,500 years!
What else have we learned about the Great Orion nebula in recent years? Try the discovery of 13 drifting gas planets. These rare, “free-floating” objects were confirmed by Patrick Roche of the University of Oxford and Philip Lucas of the University of Hertfordshire just before the turn of the century. They were found with the Hubble Space Telescope while looking for faint stars and brown dwarfs. As he explained:
“The objects are likely to be large gas planets similar in size to Jupiter and consisting primarily of hydrogen and helium. From the measured brightness and the known distance to the Orion nebula, we knew they did not have enough material for any nuclear processing in their interiors.”
Orion’s Horsehead Nebula Credit & Copyright Ryan Steinberg & Family, Adam Block, NOAO, AURA, NSF
Chances are very good these planets may be failed stars – much like our own Jupiter. But these planets don’t orbit a star the same way our solar system’s planets orbit the Sun… they simply roam around. Dr. Roche said that the 13 objects “probably formed in a different way from the planets in our solar system” in that they were not made “out of the residue of material left over from the birth of the sun.”
Instead, they formed “like stars via the collapse of a cloud of cold gas,” explained Lucas. “But they possess most of the physical properties and structure of gas giant planets,” added Lucas.
History of Observation:
Messier 42 was possibly discovered 1610 by Nicholas-Claude Fabri de Peiresc and was recorded by by Johann Baptist Cysatus, Jesuit astronomer, in 1611. For fans of the great Galileo, he was the first to mention the Trapezium cluster in 1617, but did not see the nebula. (However, do not despair! For it is my belief that he was simply using too much magnification and therefore could not see the extent of what he was looking at.)
The first known drawing of the Orion nebula was created by Giovanni Batista Hodierna, and after all of these documents were lost, the Orion nebula was once again credited to Christian Huygens 1656, documented by Edmund Halley in 1716. It then went on to Jean-Jacques d’Ortous de Mairan in his nebulae descriptions, to be added by Philippe Loys de Chéseaux to his list, expounded by Guillaume Legentil in his review.
Horsehead Nebula at the Orion. Credit & Copyright Adam Block, Mt. Lemmon SkyCenter, U. Arizona
At last, Charles Messier added the nebula to his catalog on March 4, 1769. As he wrote of the stunning objectL
“The drawing of the nebula in Orion, which I present at the Academy, has been traced with the greatest care which is possible for me. The nebula is represented there as I have seen it several times with an excellent achromatic refractor of three and a half feet focal length, with a triple lens, of 40 lignes [3.5 inches] aperture, and which magnifies 68 times. This telescope made in London by Dollond, belongs to M. President de Saron. I have examined that nebula with the greatest attention, in an entirely serene sky, as follows: February 25 & 26, 1773. Orion in the Meridian. March 19, between 8 & 9 o’clock in the evening. [March] 23, between 7 & 8 o’clock. The 25th & 26th of the same month, at the same time. These combined observations and the drawings brought together, have enabled me to represent with care and precision its shape and its appearances.
“This drawing will serve to recognize, in following times, if this nebula is subject to any changes. There may be already cause to presume this; for, if one compares this drawing with those given by MM. Huygens, Picard, Mairan and by le Gentil, one finds there such a change that one would have difficulty to figure out that this was the same. I will make these observations in the following with the same telescope and the same magnification. In the figure which I give, the circle represents the field of the telescope in its true aperture; it contains the Nebula and thirty Stars of different magnitudes. The figure is inverted, as it is shown in the instrument; one recognizes there also the extension and the limits of this nebula, the sensible difference between its clearest or most apparent light with that which merges gradually with the background of the sky. The jet of light, directed from the star no. 8 to the star no. 9, passing by a small star of the 10th magnitude, which is extremely rare, as well as the light directed to the star no. 10, and that which is opposite, where there are the eight stars contained in the nebula; among these stars, there is one of the eighth magnitude, six of the tenth, and the eighth of the eleventh magnitude. M. de Mairan, in his Traite de l’Aurore Boreale, speaks of the star no. 7. I report it in my drawing below such as it is at present, and as I have seen; so to speak surrounded by a thin nebulosity. In the night of October 14 to 15, 1764, in a serene sky, I determined with regard to Theta in the nebula, the positions of the more apparent stars in right ascension and declination, by the means of a micrometer adapted to a Newtonian telescope of 4 1/2 feet length. These stars are numbered up to ten; I have reported them in the drawing containing the field of the telescope; and an eleventh of them is beyond the circle. The positions of the stars which are not marked with numbers have been fixed by estimating their relative alignments. One will know easily also the magnitude of the Stars by the model which I have reported on the figure. Those of the tenth and the eleventh magnitude are absolutely telescopic and very difficult to find.”
However, it would be Sir William Herschel who would devote much love, time, and attention to the Great Orion Nebula – even though his findings would never be made public. As a true master observer, he had quite a talent for sensing what truly might lay beyond the boundary:
“In 1783, I reexamined the nebulous star, and found it to be faintly surrounded with a circular glory of whitish nebulosity, faintly joined to the great nebula. About the latter end of the same year I remarked that it was not equally surrounded, but most nebulous toward the south. In 1784 I began to entertain an opinion that the star was not connected with the nebulosity of the great nebula in Orion, but was one of those which are scattered over that part of the heavens. In 1801, 1806, and 1810 this opinion was fully confirmed, by the gradual change which happened in the great nebula, to which the nebulosity surrounding this star belongs. For the intensity of the light about the nebulous star had by this time been considerably reduced, by attenuation or dissipation of nebulous matter; and it seemed now to be pretty evident that the star is far behind the nebulous matter, and that consequently its light in passing through it is scattered and deflected, so as to produce the appearance of a nebulous star. A similar phenomenon may be seen whenever a planet or a star of the 1st or 2nd magnitude happens to be involved in haziness; for a diffused circular light will then be seen, to which, but in a much inferior degree, that which surrounds this nebulous star bears a great resemblance.”
But of course, the great Sir William Herschel also had nights from his many notes on M42 where he simply said: “The nebula in Orion which I saw by the front-view was so glaring and beautiful that I could not think of taking any place of its extent.”
Locating Messier 42:
Finding Messier 42 is very easy from a dark sky location by centering on the glowing region in the center of Orion’s “sword”. However, from urban locations, these stars might not be visible, so aim your binoculars or telescope about a fist width south of the three prominent stars that make the asterism known as Orion’s Belt. It’s a very bright and large object well suited to all sky conditions and instruments!
This chart shows the location of Messier 78 in the famous constellation of Orion (The Hunter). Credit: ESO, IAU and Sky & Telescope
Remember to use low power to get the full majesty of M42 and to increase magnification to study various regions. And trust us when we tell you, you are in for some pretty awesome viewing!
And of course, here are the quick facts on Messier 42 to help you get started:
Object Name: Messier 42 Alternative Designations: M42, NGC 1976, The Great Orion Nebula, Home of the Trapezium Object Type: Emission and Reflection Nebula with Open Galactic Star Cluster Constellation: Orion Right Ascension: 05 : 35.4 (h:m) Declination: -05 : 27 (deg:m) Distance: 1.3 (kly) Visual Brightness: 4.0 (mag) Apparent Dimension: 85×60 (arc min)
Composite Spitzer, Hubble, and Chandra image of supernova remnant Cassiopeia A. A new study shows that a supernova as far away as 50 light years could have devastating effects on life on Earth. (NASA/JPL-Caltech/STScI/CXC/SAO)
There are a lot of ways that life on Earth could come to an end: an asteroid strike, global climate catastrophe, or nuclear war are among them. But perhaps the most haunting would be death by supernova, because there’s absolutely nothing we could do about it. We’d be sitting ducks.
New research suggest that a supernova’s kill zone is bigger than we thought; about 25 light years bigger, to be exact.
Iron in the Ocean
In 2016, researchers confirmed that Earth has been hit with the effects from multiple supernovae. The presence of iron 60 in the seabed confirms it. Iron 60 is an isotope of iron produced in supernova explosions, and it was found in fossilized bacteria in sediments on the ocean floor. Those iron 60 remnants suggest that two supernovae exploded near our solar system, one between 6.5 to 8.7 million years ago, and another as recently as 2 million years ago.
Iron 60 is extremely rare here on Earth because it has a short half life of 2.6 million years. Any of the iron 60 created at the time of Earth’s formation would have decayed into something else by now. So when researchers found the iron 60 on the ocean floor, they reasoned that it must have another source, and that logical source is a supernova.
This evidence was the smoking gun for the idea that Earth has been struck by supernovae. But the questions it begs are, what effect did that supernova have on life on Earth? And how far away do we have to be from a supernova to be safe?
“…we can look for events in the history of the Earth that might be connected to them (supernova events).” – Dr. Adrian Melott, Astrophysicist, University of Kansas.
In a press release from the University of Kansas, astrophysicist Adrian Melott talked about recent research into supernovae and the effects they can have on Earth. “This research essentially proves that certain events happened in the not-too-distant past,” said Melott, a KU professor of physics and astronomy. “They make it clear approximately when they happened and how far away they were. Knowing that, we can consider what the effect may have been with definite numbers. Then we can look for events in the history of the Earth that might be connected to them.”
Earlier work suggested that a supernova kill zone is about 25-30 light years. If a supernova exploded that close to Earth, it would trigger a mass extinction. Bye-bye humanity. But new work suggests that 25 light years is an under-estimation, and that a supernova 50 light years away would be powerful enough to cause a mass extinction.
Supernovae: A Force Driving Evolution?
But extinction is just one effect a supernova could have on Earth. Supernovae can have other effects, and they might not all be negative. It’s possible that a supernovae about 2.6 million years ago even drove human evolution.
“Our local research group is working on figuring out what the effects were likely to have been,” Melott said. “We really don’t know. The events weren’t close enough to cause a big mass extinction or severe effects, but not so far away that we can ignore them either. We’re trying to decide if we should expect to have seen any effects on the ground on the Earth.”
Melott and his colleagues have written a new paper that focuses on the effects a supernova might have on Earth. In a new paper titled “A SUPERNOVA AT 50 PC: EFFECTS ON THE EARTH’S ATMOSPHERE AND BIOTA”, Melott and a team of researchers tried to shed light on Earth-supernova interactions.
The Local Bubble
There are a number of variables that come into play when trying to determine the effects of a supernova, and one of them is the idea of the Local Bubble. The Local Bubble itself is the result of one or more supernova explosion that occurred as long as 20 million years ago. The Local Bubble is a 300 light year diameter bubble of expanding gas in our arm of the Milky Way galaxy, where our Solar System currently resides. We’ve been travelling through it for the last five to ten million years. Inside this bubble, the magnetic field is weak and disordered.
Melott’s paper focused on the effects that a supernova about 2.6 million years ago would have on Earth in two instances: while both were within the Local Bubble, and while both were outside the Local Bubble.
The disrupted magnetic field inside the Local Bubble can in essence magnify the effects a supernova can have on Earth. It can increase the cosmic rays that reach Earth by a factor of a few hundred. This can increase the ionization in the Earth’s troposphere, which mean that life on Earth would be hit with more radiation.
Outside the Local Bubble, the magnetic field is more ordered, so the effect depends on the orientation of the magnetic field. The ordered magnetic field can either aim more radiation at Earth, or it could in a sense deflect it, much like our magnetosphere does now.
Focusing on the Pleistocene
Melott’s paper looks into the connection between the supernova and the global cooling that took place during the Pleistocene epoch about 2.6 million years ago. There was no mass extinction at that time, but there was an elevated extinction rate.
According to the paper, it’s possible that increased radiation from a supernova could have changed cloud formation, which would help explain a number of things that happened at the beginning of the Pleistocene. There was increased glaciation, increased species extinction, and Africa grew cooler and changed from predominantly forests to semi-arid grasslands.
Cancer and Mutation
As the paper concludes, it is difficult to know exactly what happened to Earth 2.6 million years ago when a supernova exploded in our vicinity. And it’s difficult to pinpoint an exact distance at which life on Earth would be in trouble.
But high levels of radiation from a supernova could increase the cancer rate, which could contribute to extinction. It could also increase the mutation rate, another contributor to extinction. At the highest levels modeled in this study, the radiation could even reach one kilometer deep into the ocean.
There is no real record of increased cancer in the fossil record, so this study is hampered in that sense. But overall, it’s a fascinating look at the possible interplay between cosmic events and how we and the rest of life on Earth evolved.
Using data from Chandra and other telescopes, astronomers have found a possible "recoiling" black hole. Credit: NASA/CXC/M.Weiss
When galaxies collide, all manner of chaos can ensue. Though the process takes millions of years, the merger of two galaxies can result in Supermassive Black Holes (SMBHs, which reside at their centers) merging and becoming even larger. It can also result in stars being kicked out of their galaxies, sending them and even their systems of planets into space as “rogue stars“.
But according to a new study by an international team of astronomers, it appears that in some cases, SMBHs could also be ejected from their galaxies after a merger occurs. Using data from NASA’s Chandra X-ray Observatory and other telescopes, the team detected what could be a “renegade supermassive black hole” that is traveling away from its galaxy.
According to the team’s study – which appeared in the Astrophysical Journal under the title A Potential Recoiling Supermassive Black Hole, CXO J101527.2+625911 – the renegade black hole was detected at a distance of about 3.9 billion light years from Earth. It appears to have come from within an elliptical galaxy, and contains the equivalent of 160 million times the mass of our Sun.
Hubble data showing the two bright points near the middle of the galaxy. Credit: NASA/CXC/NRAO/D.-C.Kim/STScI
The team found this black hole while searching through thousands of galaxies for evidence of black holes that showed signs of being in motion. This consisted of sifting through data obtained by the Chandra X-ray telescope for bright X-ray sources – a common feature of rapidly-growing SMBHs – that were observed as part of the Sloan Digital Sky Survey (SDSS).
They then looked at Hubble data of all these X-ray bright galaxies to see if it would reveal two bright peaks at the center of any. These bright peaks would be a telltale indication that a pair of supermassive black holes were present, or that a recoiling black hole was moving away from the center of the galaxy. Last, the astronomers examined the SDSS spectral data, which shows how the amount of optical light varies with wavelength.
From all of this, the researchers invariably found what they considered to be a good candidate for a renegade black hole. With the help data from the SDSS and the Keck telescope in Hawaii, they determined that this candidate was located near, but visibly offset from, the center of its galaxy. They also noted that it had a velocity that was different from the galaxy – properties which suggested that it was moving on its own.
The image below, which was generated from Hubble data, shows the two bright points near the center of the galaxy. Whereas the one on the left was located within the center, the one on the right (the renegade SMBH) was located about 3,000 light years away from the center. Between the X-ray and optical data, all indications pointed towards it being a black hole that was kicked from its galaxy.
The bright X-ray source detected with Chandra (left), and data obtained from the SDSS and the Keck telescope in Hawaii. Credit: NASA/CXC/NRAO/D.-C.Kim/STScI
In terms of what could have caused this, the team ventured that the back hole might have “recoiled” when two smaller SMBHs collided and merged. This collision would have generated gravitational waves that could have then pushed the black hole out of the galaxy’s center. They further ventured that the black hole may have formed and been set in motion by the collision of two smaller black holes.
Another possible explanation is that two SMBHs are located in the center of this galaxy, but one of them is not producing detectable radiation – which would mean that it is growing too slowly. However, the researchers favor the explanation that what they observed was a renegade black hole, as it seems to be more consistent with the evidence. For example, their study showed signs that the host galaxy was experiencing some disturbance in its outer regions.
This is a possible indication that the merger between the two galaxies occurred in the relatively recent past. Since SMBH mergers are thought to occur when their host galaxies merge, this reservation favors the renegade black hole theory. In addition, the data showed that in this galaxy, stars were forming at a high rate. This agrees with computer simulations that predict that merging galaxies experience an enhanced rate of star formation.
But of course, additional researches is needed before any conclusions can be reached. In the meantime, the findings are likely to be of particular interest to astronomers. Not only does this study involve a truly rare phenomenon – a SMBH that is in motion, rather than resting at the center of a galaxy – but the unique properties involved could help us to learn more about these rare and enigmatic features.
Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.
For one, the study of SMBHs could reveal more about the rate and direction of spin of these enigmatic objects before they merge. From this, astronomers would be able to better predict when and where SMBHs are about to merge. Studying the speed of recoiling black holes could also reveal additional information about gravitational waves, which could unlock additional secrets about the nature of space time.
And above all, witnessing a renegade black hole is an opportunity to see some pretty amazing forces at work. Assuming the observations are correct, there will no doubt be follow-up surveys designed to see where the SMBH is traveling and what effect it is having on the surrounding cosmic environment.
Ever since the 1970s, scientists have been of the opinion that most galaxies have SMBHs at their center. In the years and decades that followed, research confirmed the presence of black holes not only at the center of our galaxy – Sagittarius A* – but at the center of all almost all known massive galaxies. Ranging in mass from the hundreds of thousands to billions of Solar masses, these objects exert a powerful influence on their respective galaxies.
Be sure to enjoy this video, courtesy of the Chandra X-Ray Observatory:
Asteroid impacts on Mars could have generated supersonic winds that shaped the surface, according to a new study. Credit: geol.umd.edu
The study of another planet’s surface features can provide a window into its deep past. Take Mars for example, a planet whose surface is a mishmash of features that speak volumes. In addition to ancient volcanoes and alluvial fans that are indications of past geological activity and liquid water once flowing on the surface, there are also the many impact craters that dot its surface.
In some cases, these impact craters have strange bright streaks emanating from them, ones which reach much farther than basic ejecta patterns would allow. According to a new research study by a team from Brown University, these features are the result of large impacts that generated massive plumes. These would have interacted with Mars’ atmosphere, they argue, causing supersonic winds that scoured the surface.
These features were noticed years ago by Professor Peter H. Schultz, a professor of geological science with the Department of Earth, Environmental, and Planetary Sciences (DEEPS) at Brown University. When studying images taken at night by the Mars Odyssey orbiter using its THEMIS instrument, he noticed steaks that only appeared when imaged in the infrared wavelength.
Artist’s conception of the Mars Odyssey spacecraft. Credit: NASA/JPL
These streaks were only visible in IR because it was only at this wavelength that contrasts in heat retention on the surface were visible. Essentially, brighter regions at night indicate surfaces that retain more heat during the day and take longer to cool. As Schultz explained in a Brown University press release, this allowed for features to be discerned that would otherwise not be noticed:
“You couldn’t see these things at all in visible wavelength images, but in the nighttime infrared they’re very bright. Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare.”
Along with Stephanie N. Quintana, a graduate student from DEEPS, the two began to consider other explanations that went beyond basic ejecta patterns. As they indicate in their study – which recently appeared in the journal Icarus under the title “Impact-generated winds on Mars” – this consisted of combining geological observations, laboratory impact experiments and computer modeling of impact processes.
Ultimately, Schultz and Quintana concluded that crater-forming impacts led to vortex-like storms that reached speeds of up to 800 km/h (500 mph) – in other words, the equivalent of an F8 tornado here on Earth. These storms would have scoured the surface and ultimately led to the observed streak patterns. This conclusion was based in part on work Schultz has done in the past at NASA’s Vertical Gun Range.
An infrared image revealing strange bright streaks extending from Santa Fe crater on Mars. Credit: NASA/JPL-Caltech/Arizona State University.
This high-powered cannon, which can fire projectiles at speeds up to 24,000 km/h (15,000 mph), is used to conduct impact experiments. These experiments have shown that during an impact event, vapor plumes travel outwards from the impact point (just above the surface) at incredible speeds. For the sake of their study, Schultz and Quintana scaled the size of the impacts up, to the point where they corresponded to the impact craters on Mars.
The results indicated that the vapor plume speed would be supersonic, and that its interaction with the Martian atmosphere would generate powerful winds. However, the plume and associated winds would not be responsible for the strange streaks themselves. Since they would be travelling just above the surface, they would not be capable of causing the kind of deep scouring that exists in the streaked areas.
Instead, Schultz and Quintana showed that when the plume struck a raised surface feature – like the ridges of a smaller impact crater – it would create more powerful vortices that would then fall to the surface. It is these, according to their study, that are responsible for the scouring patterns they observed. This conclusion was based on the fact that bright streaks were almost always associated with the downward side of a crater rim.
IR images showing the correlation between the streaks and smaller craters that were in place when the larger crater was formed. Credit: NASA/JPL-Caltech/Arizona State University
As Schultz explained, the study of these streaks could prove useful in helping to establish that rate at which erosion and dust deposition occurs on the Martian surface in certain areas:
“Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that’s what gives us these streaks. We know these formed at the same time as these large craters, and we can date the age of the craters. So now we have a template for looking at erosion.”
In addition, these streaks could reveal additional information about the state of Mars during the time of impacts. For example, Schultz and Quintana noted that the streaks appear to form around craters that are about 20 km (12.4 mi) in diameter, but not always. Their experiments also revealed that the presence of volatile compounds (such as surface or subsurface water ice) would affect the amount of vapor generated by an impact.
In other words, the presence of streaks around some craters and not others could indicate where and when there was water ice on the Martian surface in the past. It has been known for some time that the disappearance of Mars’ atmosphere over the course of several hundred million years also resulted in the loss of its surface water. By being able to put dates to impact events, we might be able to learn more about Mars’ fateful transformation.
The study of these streaks could also be used to differentiate between the impacts of asteroids and comets on Mars – the latter of which would have had higher concentrations of water ice in them. Once again, detailed studies of Mars’ surface features are allowing scientists to construct a more detailed timeline of its evolution, thus determining how and when it became the cold, dry place we know today!
The Constellation Chamaeleon. Credit: Till Credner/AlltheSky.com
Welcome back to Constellation Friday! Today, in honor of the late and great Tammy Plotner, we will be dealing with that famous lizard that specializes at blending in – the Chamaeleon constellation!
In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age.
In time, this list would come to be expanded as astronomers became aware of more asterisms in the night sky. One of these is Chamaeleon, a small constellation located in the southern sky that was first defined in the 16th century. This constellation was appropriately named, given its ability to blend into the background! Today, it is one of the 88 constellations recognized by the IAU.
Name and Meaning:
Since Chamaeleon was unknown to the ancient Greeks and Romans, it has no mythology associated with it, but it’s not hard to understand how it came about its fanciful name. As exploration of the southern hemisphere began, what biological wonders were discovered! Can you imagine how odd a creature that could change its skin color to match its surroundings would be to someone who wasn’t familiar with lizards?
Map of the dark molecular clouds associated with the Chamaeleon constellation. Credit: Roberto Mura
Small wonder that a constellation that blended right in with the background stars could be considered a “chamaeleon” or that it might be pictured sticking its long tongue out to capture its insectile constellation neighbor – Musca the “fly”!
History of Observation:
Chamaeleon was one of twelve constellations created by Pieter Dirkszoon Keyser and Frederick de Houtman between 1595 and 1597. Both were Dutch navigators and early astronomical explorers who made attempts to chart southern hemisphere skies. Their work was added to Johann Bayer’s “Uranometeria” catalog in 1603, where Chamaeleon was first introduced as one of the 12 new southern constellations and its stars given Bayer designations.
To this day, Chamaeleon remain as one of the 88 modern constellations recognized by the IAU and it is bordered by Musca, Carina, Volans, Mensa, Octans and Apus. It contains only 3 main stars, the brightest of which is 4th magnitude Alpha – but it also has 16 Bayer/Flamsteed designated stars within its boundaries.
Notable Features:
The Chamaeleon constellation is home to several notable stars. These include Alpha Chamaeleontis, a spectral type F5III star located approximately 63.5 light years from Earth. Beta Chamaeleontis is a main sequence star that is approximately 270 light years distant. This star is the third brightest in the constellation, after Alpha and Gamma Chamaeleontis.
Artist’s concept of “hot Jupiter”, a Jupiter-sized planet orbiting closely to its star. Credit: NASA/JPL-Caltech
And then there’s HD 63454, a K-type main sequence star located approximately 116.7 light years away. It lies near the south celestial pole and is slightly cooler and less luminous than the Sun. In February of 2005, a hot Jupiter-like planet (HD 63454 b) was discovered orbiting the star.
The “Chamaeleon” also disguises itself with a huge number of dark molecular clouds that are often referred to as the “Chamaeleon Cloud Complex”. Situation about 15 degrees below the galactic plane, it is accepted is one of the closest low mass star forming regions to the Sun with a distance of about 400 to 600 light years.
Within these clouds are pre-main sequence star candidates, and low-mass T Tauri stars. The southern region of the Chamaeleon Cloud is a complex pattern of dark knots connected by elongated, dark, wavy filaments, with a serpentine-like shape. Bright rims with finger-like extensions are apparent, and a web of very faint, extremely thin but very long and straight shining filaments.
These feeble structures, reflecting stellar light, extend over the entire Chamaeleon complex and are considered very young – not yet capable of the type of collapse needed to introduce major star formation. Thanks to Gemini Near Infrared Spectrograph (GNIRS) on Gemini South Telescope, a very faint infrared object confirmed – a very low-mass, newborn brown dwarf star and the lowest mass brown dwarf star found to date in the Chamaeleon I cloud complex.
A newly formed star lights up the surrounding cosmic clouds in this image from ESO’s La Silla Observatory in Chile. Credit: ESO
Chamaeleon is also home to the Eta Chamaeleontis Cluster (aka. Mamajek 1). This open star cluster, which is centered on the star Eta Chamaeleontis, is approximately 316 light years distant and believed to be around eight million years old. The cluster was discovered in 1999 and consists of 12 or so relatively young stars. It was also the first open cluster discovered because of its X-ray emissions its member stars emit.
Finding Chamaeleon:
Chamaeleon is visible at latitudes between +0° and -90° and is best seen at culmination during the month of April. Now take out your telescope and aim it towards Eta for a look at newly discovered galactic star cluster – the Eta Chamaeleontis cluster – Mamajek 1. In 1999, a cluster of young, X-ray-emitting stars was found in the vicinity of eta Chamaeleontis from a deep ROSAT high-resolution imager observation.
They are believed to be pre-main-sequence weak-lined T Tauri stars, with an age of up to 12 million years old. The cluster itself is far from any significant molecular cloud and thus it has mysterious origins – not sharing proper motions with other young stars in the Chamaeleon region. There’s every possibility it could be a moving star cluster that’s a part of the Scorpius/Centaurus OB star association!
For binoculars, take a look at fourth magnitude Alpha Chamaeleontis. It is a rare class F white giant star that is about 63.5 light years from Earth. It is estimated to be about 1.5 billion years old. Its spectrum shows it to be a older giant with a dead helium core, yet its luminosity and temperature show it to be a younger dwarf.
The location of the Chamaeleon Constellation. Credit: IAU /Sky&Telescope magazine
Now point your binoculars or telescope towards Delta Chamaeleontis. While these two stars aren’t physically connect to one another, the visual double star is exceptionally pleasing with one orange component and one blue.
Last, but not least, take a look at Gamma Chamaeleontis. Although the south celestial pole currently lacks a bright star like Polaris to mark its position, the precession of the equinoxes will change that. One day – in the next 7500 years – the south celestial pole will pass close to the stars Gamma Chamaeleontis. But don’t wait up…
Artist's rendering of a possible Europa Lander mission, which would explore the surface of the icy moon in the coming decades. Credit:: NASA/JPL-Caltech
Between the Europa Clipper and the proposed Europa Lander, NASA has made it clear that it intends to send a mission to this icy moon of Jupiter in the coming decade. Ever since the Voyager 1 and 2 probes conducted their historic flybys of the moon in 1973 and 1974 – which offered the first indications of a warm-water ocean in the moon’s interior – scientists have been eager to peak beneath the surface and see what is there.
Towards this end, NASA has issued a grant to a team of researchers from Arizona State University to build and test a specially-designed seismometer that the lander would use to listen to Europa’s interior. Known as the Seismometer for Exploring the Subsurface of Europa (SESE), this device will help scientists determine if the interior of Europa is conducive to life.
According to the profile for the Europa Lander, this microphone would be mounted to the robotic probe. Once it reached the surface of the moon, the seismometer would begin collecting information on Europa’s subsurface environment. This would include data on its natural tides and movements within the shell, which would determine the icy surface’s thickness.
Image of Europa’s ice shell, taken by the Galileo spacecraft, of fractured “chaos terrain”. Credit: NASA/JPL-Caltech
It would also determine if the surface has pockets of water – i.e. subsurface lakes – and see how often water rises to the surface. For some time, scientists have suspected that Europa’s “chaos terrain” would be the ideal place to search for evidence of life. These features, which are basically a jumbled mess of ridges, cracks, and plains, are believed to be spots where the subsurface ocean is interacting with the icy crust.
As such, any evidence of organic molecules or biological organisms would be easiest to find there. In addition, astronomers have also detected water plumes coming from Europa’s surface. These are also considered to be one of the best bets for finding evidence of life in the interior. But before they can be explored directly, determining where reservoirs of water reside beneath the ice and if they are connected to the interior ocean is paramount.
And this is where instruments like the SESE would come into play. Hongyu Yu is an exploration system engineer from ASU’s School of Earth and Space Exploration and the leader of the SESE team. As he stated in a recent article by ASU Now, “We want to hear what Europa has to tell us. And that means putting a sensitive ‘ear’ on Europa’s surface.”
While the idea of a Europa Lander is still in the concept-development stage, NASA is working to develop all the necessary components for such a mission. As such, they have provided the ASU team with a grant to develop and test their miniature seismometer, which measures no more than 10 cm (4 inches) on a side and could easily be fitted aboard a robotic lander.
Europa’s “Great Lake.” Scientists speculate many more exist throughout the shallow regions of the moon’s icy shell. Credit: Britney Schmidt/Dead Pixel FX/Univ. of Texas at Austin.
More importantly, their seismometer differs from conventional designs in that it does not rely on a mass-and-spring sensor. Such a design would be ill-suited for a mission to another body in our Solar System since it needs to be positioned upright, which requires that it be carefully planted and not disturbed. What’s more, the sensor needs to be placed within a complete vacuum to ensure accurate measurements.
By using a micro-electrical system with a liquid electrolyte for a sensor, Yu and his team have created a seismometer that can operate under a wider range of conditions. “Our design avoids all these problems,” he said. “This design has a high sensitivity to a wide range of vibrations, and it can operate at any angle to the surface. And if necessary, they can hit the ground hard on landing.”
As Lenore Dai – a chemical engineer and the director of the ASU’s School for Engineering of Matter, Transport and Energy – explained, the design also makes the SESE well suited for exploring extreme environments – like Europa’s icy surface. “We’re excited at the opportunity to develop electrolytes and polymers beyond their traditional temperature limits,” she said. “This project also exemplifies collaboration across disciplines.”
The SESE can also take a beating without compromising its sensor readings, which was tested when the team struck it with a sledgehammer and found that it still worked afterwards. According to seismologist Edward Garnero, who is also a member of the SESE team, this will come in handy. Landers typically have six to eight legs, he claims, which could be mated with seismometers to turn them into scientific instruments.
Artist’s concept of chloride salts bubbling up from Europa’s liquid ocean and reaching the frozen surface. Credit: NASA/JPL-Caltech
Having this many sensors on the lander would give scientists the ability to combine data, allowing them to overcome the issue of variable seismic vibrations recorded by each. As such, ensuring that they are rugged is a must.
“Seismometers need to connect with the solid ground to operate most effectively. If each leg carries a seismometer, these could be pushed into the surface on landing, making good contact with the ground. We can also sort out high frequency signals from longer wavelength ones. For example, small meteorites hitting the surface not too far away would produce high frequency waves, and tides of gravitational tugs from Jupiter and Europa’s neighbor moons would make long, slow waves.”
Such a device could also prove crucial to missions other “ocean worlds” within the Solar System, which include Ceres, Ganymede,Callisto,Enceladus, Titan and others. On these bodies as well, it is believed that life could very well exist in warm-water oceans that lie beneath the surface. As such, a compact, rugged seismometer that is capable of working in extreme-temperature environments would be ideal for studying their interiors.
What’s more, missions of this kind would be able to reveal where the ice sheets on these bodies are thinnest, and hence where the interior oceans are most accessible. Once that’s done, NASA and other space agencies will know exactly where to send in the probe (or possibly the robotic submarine). Though we might have to wait a few decades on that one!
