Even if you know nothing about hurricanes, an unavoidable sense of doom and destruction overtakes you when you look at this image of Hurricane Florence as it moves inexorably toward North and South Carolina.
Even if you didn’t know that the powerful storm is forecast to gain strength as it hits the coast on Friday, or that it will dump several months of rain onto the region in a mere few days, or that the storm surge could reach as high as 9 to 13 ft. If you didn’t know all those things, the picture of Florence taken from space would still fill you with foreboding.
Within Earth’s orbit, there are an estimated eighteen-thousands Near-Earth Asteroids (NEAs), objects whose orbit periodically takes them close to Earth. Because these asteroids sometimes make close flybys to Earth – and have collided with Earth in the past – they are naturally seen as a potential hazard. For this reason, scientists are dedicated to tracking NEAs, as well as studying their origin and evolution.
Shortly after Einstein published his Theory of General Relativity in 1915, physicists began to speculate about the existence of black holes. These regions of space-time from which nothing (not even light) can escape are what naturally occur at the end of most massive stars’ life cycle. While black holes are generally thought to be voracious eaters, some physicists have wondered if they could also support planetary systems of their own.
Looking to address this question, Dr. Sean Raymond – an American physicist currently at the University of Bourdeaux – created a hypothetical planetary system where a black hole lies at the center. Based on a series of gravitational calculations, he determined that a black hole would be capable of keeping nine individual Suns in a stable orbit around it, which would be able to support 550 planets within a habitable zone.
He named this hypothetical system “The Black Hole Ultimate Solar System“, which consists of a non-spinning black hole that is 1 million times as massive as the Sun. That is roughly one-quarter the mass of Sagittarius A*, the super-massive black hole (SMBH) that resides at the center of the Milky Way Galaxy (which contains 4.31 million Solar Masses).
Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.
As Raymond indicates, one of the immediate advantages of having this black hole at the center of a system is that it can support a large number of Suns. For the sake of his system, Raymond chose 9, thought he indicates that many more could be sustained thanks to the sheer gravitational influence of the central black hole. As he wrote on his website:
“Given how massive the black hole is, one ring could hold up to 75 Suns! But that would move the habitable zone outward pretty far and I don’t want the system to get too spread out. So I’ll use 9 Suns in the ring, which moves everything out by a factor of 3. Let’s put the ring at 0.5 AU, well outside the innermost stable circular orbit (at about 0.02 AU) but well inside the habitable zone (from about 2.7 to 5.4 AU).”
Another major advantage of having a black hole at the center of a system is that it shrinks what is known as the “Hill radius” (aka. Hill sphere, or Roche sphere). This is essentially the region around a planet where its gravity is dominant over that of the star it orbits, and can therefore attract satellites. According to Raymond, a planet’s Hill radius would be 100 times smaller around a million-sun black hole than around the Sun.
This means that a given region of space could stably fit 100 times more planets if they orbited a black hole instead of the Sun. As he explained:
“Planets can be super close to each other because the black hole’s gravity is so strong! If planets are little toy Hot wheels cars, most planetary systems are laid out like normal highways (side note: I love Hot wheels). Each car stays in its own lane, but the cars are much much smaller than the distance between them. Around a black hole, planetary systems can be shrunk way down to Hot wheels-sized tracks. The Hot wheels cars — our planets — don’t change at all, but they can remain stable while being much closer together. They don’t touch (that would not be stable), they are just closer together.”
This is what allows for many planets to be placed with the system’s habitable zone. Based on the Earth’s Hill radius, Raymond estimates that about six Earth-mass planets could fit into stable orbits within the same zone around our Sun. This is based on the fact that Earth-mass planets could be spaced roughly 0.1 AU from each other and maintain a stable orbit.
Given that the Sun’s habitable zone corresponds roughly to the distances between Venus and Mars – which are 0.3 and 0.5 AU away, respectively – this means there is 0.8 AUs of room to work with. However, around a black hole with 1 million Solar Masses, the closest neighboring planet could be just 1/1000th (0.001) of an AU away and still have a stable orbit.
Doing the math, this means that roughly 550 Earths could fit in the same region orbiting the black hole and its nine Suns. There is one minor drawback to this whole scenario, which is that the black hole would have to remain at its current mass. If it were to become any larger, it would cause the Hill radii of its 550 planets to shrink down further and further.
Once the Hill radius got down to the point where it was the same size as any of the Earth-mass planets, the black hole would begin to tear them apart. But at 1 million Solar masses, the black hole is capable of supporting a massive system of planets comfortably. “With our million-Sun black hole the Earth’s Hill radius (on its current orbit) would already be down to the limit, just a bit more than twice Earth’s actual radius,” he says.
Illustration of tightly-packed orbits of Earth-mass planets in orbit around the Sun (in black) vs. around a supermassive black hole (green). Credit: Sean Raymond
Lastly, Raymond considers the implications that living in such a system would have. For one, a year on any planet within the system’s habitable zone would be much shorter, owing to the fact their orbital periods would be much faster. Basically, a year would last roughly 1.6 days for planets at the inner edge of the habitable zone and 4.6 days for planets at the outer edge of the habitable zone.
In addition, on the surface of any planet in the system, the sky would be a lot more crowded! With so many planets in close orbit together, they would pass very close to one another. That essentially means that from the surface of any individual Earth, people would be able to see nearby Earths as clear as we see the Moon on some days. As Raymond illustrated:
“At closest approach (conjunction) the distance between planets is about twice the Earth-Moon distance. These planets are all Earth-sized, about 4 times larger than the Moon. This means that at conjunction each planet’s closest neighbor appears about twice the size of the full Moon in the sky. And there are two nearest neighbors, the inner and outer one. Plus, the next-nearest neighbors are twice as far away so they are still as big as the full Moon during conjunction. And four more planets that would be at least half the full Moon in size during conjunction.”
He also indicates that conjunctions would occur almost once per orbit, which would mean that every few days, there would be no shortage of giant objects passing across the sky. And of course, there would be the Sun’s themselves. Recall that scene in Star Wars where a young Luke Skywalker is watching two suns set in the desert? Well, it would a little like that, except way more cool!
According to Raymond’s calculations, the nine Suns would complete an orbit around the black hole every three hours. Every twenty minutes, one of these Suns would pass behind the black hole, taking just 49 seconds to do so. At this point, gravitational lensing would occur, where the black hole would focus the Sun’s light toward the planet and distort the apparent shape of the Sun.
To illustrate what this would look like, he provides an animation (shown above) created by @GregroxMun – a planet modeller who develops space graphics for Kerbal and other programs – using Space Engine.
While such a system may never occur in nature, it is interesting to know that such a system would be physically possible. And who knows? Perhaps a sufficiently advanced species, with the ability to tow stars and planets from one system and place them in orbit around a black hole, could fashion this Ultimate Solar System. Something for SETI researchers to be on the lookout for, perhaps?
This hypothetical exercise was the second installment in two-part series by Raymond, titled “Black holes and planets”. In the first installment, “The Black Hole Solar System“, Raymond considered what it would be like if our system orbited around a black hole-Sun binary. As he indicated, the consequences for Earth and the other Solar planets would be interesting, to say the least!
In the 1950s, famed physicist Enrico Fermi posed the question that encapsulated one of the toughest questions in the Search for Extra-Terrestrial Intelligence (SETI): “Where the heck is everybody?” What he meant was, given the age of the Universe (13.8 billion years), the sheer number of galaxies (between 1 and 2 trillion), and the overall number of planets, why has humanity still not found evidence of extra-terrestrial intelligence?
This question, which has come to be known as the “Fermi Paradox”, is something scientists continue to ponder. In a new study, a team from the University of Rochester considered that perhaps Climate Change is the reason. Using a mathematical model based on the Anthropocene, they considered how civilizations and planet systems co-evolve and whether or not intelligent species are capable of living sustainability with their environment.
Today, Climate Change is one of the most pressing issues facing humanity. Thanks to changes that have taken place in the past few centuries – i.e. the industrial revolution, population growth, the growth of urban centers and reliance on fossil fuels – humans have had a significant impact on the planet. In fact, many geologists refer to the current era as the “Anthropocene” because humanity has become the single greatest factor affecting planetary evolution.
In the future, populations are expected to grow even further, reaching about 10 billion by mid-century and over 11 billion by 2100. In that time, the number of people who live within urban centers will also increase dramatically, increasing from 54% to 66% by mid-century. As such, the quesiton of how billions of people can live sustainably has become an increasingly important one.
Prof. Frank, who is also the author of the new book Light of the Stars: Alien Worlds and the Fate of the Earth (which draws on this study), conducted this study with his colleagues in order to address the issue Climate Change in an astrobiological context. As he explained in a University of Rochester press release:
“Astrobiology is the study of life and its possibilities in a planetary context. That includes ‘exo-civilizations’ or what we usually call aliens. If we’re not the universe’s first civilization, that means there are likely to be rules for how the fate of a young civilization like our own progresses.”
Using the Anthropocene as an example, one can see how civilization-planet systems co-evolve, and how a civilization can endanger itself through growth and expansion – in what is known as a “progress trap“. Basically, as civilizations grow, they consume more of the planet’s resources, which causes changes in the planet’s conditions. In this sense, the fate of a civilization comes down to how they use their planet’s resources.
In order to illustrate this process Frank and his collaborators developed a mathematical model that considers civilizations and planets as a whole. As Prof. Frank explained:
“The point is to recognize that driving climate change may be something generic. The laws of physics demand that any young population, building an energy-intensive civilization like ours, is going to have feedback on its planet. Seeing climate change in this cosmic context may give us better insight into what’s happening to us now and how to deal with it.”
The model was also based on case studies of extinct civilizations, which included the famous example of what became of the inhabitants of Rapa Nui (aka. Easter Island). According to archaeological studies, the people of the South Pacific began colonizing this island between 400 and 700 CE and its population peaked at 10,000 sometime between 1200 and 1500 CE.
Professor Adam Frank, who led the study in how civilization-planet systems evolve. Credit: University of Rochester photo / J. Adam Fenster
By the 18th century, however, the inhabitants had depleted their resources and the population declined to just 2000. This example raises the important concept known as “carrying capacity”, which is the maximum number of species an environment can support. As Frank explained, Climate Change is essentially how the Earth responds to the expansion of our civilization:
“If you go through really strong climate change, then your carrying capacity may drop, because, for example, large-scale agriculture might be strongly disrupted. Imagine if climate change caused rain to stop falling in the Midwest. We wouldn’t be able to grow food, and our population would diminish.”
Using their mathematical model, the team identified four potential scenarios that might occur on a planet. These include the Die-Off scenario, the Sustainability scenario, the Collapse Without Resource Change scenario, and the Collapse With Resource Change scenario. In the Die-Off scenario, the population and the planet’s state (for example, average temperatures) rise very quickly.
This would eventually lead to a population peak and then a rapid decline as changing planetary conditions make it harder for the majority of the population to survive. Eventually, a steady population level would be achieved, but it would only be a fraction of what the peak population was. This scenario occurs when civilizations are unwilling or unable to change from high-impact resources (i.e. oil, coal, clear-cutting) to sustainable ones (renewable energy).
Four scenarios for the fate of civilizations and their planets, based on mathematical models developed by Adam Frank and his collaborators. Credit: University of Rochester illustration / Michael Osadciw
In the Sustainability scenario, the population and planetary conditions both rise, but eventually come to together with steady values, thus avoiding any catastrophic effects. This scenario occurs when civilizations recognize that environmental changes threaten their existence and successfully make the transition from high-impact resources to sustainable ones.
The final two scenarios – Collapse Without Resource Change and Collapse With Resource Change – differ in one key respect. In the former, the population and temperature both rise rapidly until the population reaches a peak and begins to drop rapidly – though it is not clear if the species itself survives. In the latter, the population and temperature rise rapidly, but the populations recognizes the danger and makes the transition. Unfortunately, the change comes too late and the population collapses anyway.
At present, scientists cannot say with any confidence which of these fates will be the one humanity faces. Perhaps we will make the transition before it is too late, perhaps not. But in the meantime, Frank and his colleagues hope to use more detailed models to predict how planets will respond to civilizations and the different ways they consume energy and resources in order to grow.
From this, scientists may be able to refine their predictions of what awaits us in this century and the next. It is during this time that crucial changes will be taking place, which include the aforementioned population growth, and the steady rise in temperatures. For instance, based on two scenarios that measured CO2 increases by the year 2100, NASA indicated that global temperatures could rise by either 2.5 °C (4.5 °F) or 4.4 °C (8 °F).
In the former scenario, where CO2 levels reached 550 ppm by 2100, the changes would be sustainable. But in the latter scenario, where CO2 levels reached 800 ppm, the changes would cause widespread disruption to systems that billions of humans depends upon for their livelihood and survival. Worse than that, life would become untenable in certain areas of the world, leading to massive displacement and humanitarian crises.
In addition to offering a possible resolution for the Fermi Paradox, this study offers some helpful advice for human beings. By thinking of civilizations and planets as a whole – be they Earth or exoplanets – researchers will be able to better predict what changes will be necessary for human civilization to survive. As Frank warned, it is absolutely essential that humanity mobilize now to ensure that the worst-case scenario does not occur here on Earth:
“If you change the earth’s climate enough, you might not be able to change it back. Even if you backed off and started to use solar or other less impactful resources, it could be too late, because the planet has already been changing. These models show we can’t just think about a population evolving on its own. We have to think about our planets and civilizations co-evolving.”
And be sure to enjoy this video that addresses Prof. Frank and his team’s research, courtesy of the University of Rochester:
The purpose of this new generation of satellites is to improve the forecasts of weather, oceans, the environment and space weather by providing faster and more detailed data, real-time images, and advanced monitoring. Recently, the satellite’s Advanced Baseline Imager (ABI) made its debut by releasing its “first light“, which just happened to be some beautiful and breathtaking images of Earth from space.
The image featured above was taken on May 20th, 2018, where GOES-17 captured the sunset over Earth’s Western Hemisphere. This image was taken when the satellite was at a distance of 35,405 km (22,000 miles) from Earth and was presented in “GeoColor”, which captures features of the Earth’s surface and atmosphere in vivid detail and colors that are familiar to the human eye.
Compared to previous GOES satellites, GOES-17 can collect three times more data at four times the image resolution, and scan the planet five times faster than previous probes. These abilities were put to the test as the ABI created its beautiful images of Earth using two visible bands (blue and red) and one near-infrared “vegetation” band, and one of the ABI’s “longwave” infrared bands.
When combined as a “GeoColor” image, these bands provide valuable information for monitoring dust, haze, smoke, fog, clouds and winds in the atmosphere – which allows meteorologists to monitor and forecast where severe weather events will take place. It also allows scientists to monitor vegetation patterns to see how weather conditions can lead to increased drought or the expansions of greenery.
It also results in pictures depicting Earth in vivid and colorful detail, as you can plainly see! The satellite is currently in its post-launch checkout testing phase, where controllers on Earth are busy calibrating its instruments and systems and validating them for use. The imagery acquired by the ABI is one such example, which served as a preliminary check to ensure that the imaging instrument will function properly.
Other images included the picture of a series of dynamic marine stratocumulus clouds (shown above), which was captured by the satellite’s ABI off the western coast of Chile in the the southeastern Pacific Ocean. Once again, the improved resolution and sensitivity of the GOES-17 allows it to monitor clouds in our atmosphere with amazing detail and clarity.
GOES-17 also captured a deck of low level stratus clouds covering the southern California coast (above) and smoke plumes created by wildfires in central and northern Saskatchewan, Canada (below). These two images were also acquired by the ABI on May 20th, 2018, and demonstrate how effective GOES-17 will be when it comes to monitoring weather patterns, events that can trigger fires (i.e. lighting), and the resulting fires themselves.
Alongside GOES-17, NOAA’s operational geostationary constellation also consists of GOES-16 (operating as GOES-East), GOES-15 (operating as GOES-West), and GOES-14 – operating as the on-orbit spare. This satellite constellation is currently in good working order and is monitoring weather across the US and the planet each day.
While this data is still preliminary and non-operational, it does provide a good preview of what the GOES-17 can do. In the coming years, it and its third and fourth-generation cousins – GOES-T and GOES-U – will allow Earth observers to monitor weather, climate change and natural disasters with far greater detail, allowing for better early warning and response efforts.
To see more full-resolution images from the GOES-17 ABI, go to the NOAA page.
It is a well-known fact among Earth scientists that our planet periodically undergoes major changes in its climate. Over the course of the past 200 million years, our planet has experienced four major geological periods (the Triassic, Jurassic and Cretaceous and Cenozoic) and one major ice age (the Pliocene-Quaternary glaciation), all of which had a drastic impact on plant and animal life, as well as effecting the course of species evolution.
For decades, geologists have also understood that these changes are due in part to gradual shifts in the Earth’s orbit, which are caused by Venus and Jupiter, and repeat regularly every 405,000 years. But it was not until recently that a team of geologists and Earth scientists unearthed the first evidence of these changes – sediments and rock core samples that provide a geological record of how and when these changes took place.
Professor Dennis Kent with part of a 1,700-foot-long rock core obtained from Petrified Forest National Park in Arizona. Credit: Nick Romanenko/Rutgers University
As noted, the idea that Earth experiences periodic changes in its climate (which are related to changes in its orbit) has been understood for almost a century. These changes consist of Milankovitch Cycles, which consist of a 100,000-year cycle in the eccentricity of Earth’s orbit, a 41,000-year cycle in the tilt of Earth’s axis relative to its orbital plane, and a 21,000-year cycle caused by changes in the planet’s axis.
Combined with the 405,000-year swing, which is the result of Venus and Jupiter’s gravitational influence, these shifts cause changes in how much solar energy reaches parts of our planet, which in turn influences Earth’s climate. Based on fossil records, these cycles are also known to have had a profound impact on life on Earth, which likely had an effect on the course of species of evolution. As Prof. Bent explained in a Rutgers Today press release:
“The climate cycles are directly related to how Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes. The Earth’s orbit changes from close to perfectly circular to about 5 percent elongated especially every 405,000 years.”
For the sake of their study, Prof. Kent and his colleagues obtained sediment samples from the Newark basin, a prehistoric lake that spanned most of New Jersey, and a core rock sample from the Chinle Formation in Petrified Forest National Park in Arizona. This core rock measured about 518 meters (1700 feet) long, 6.35 cm (2.5 inches) in diameter, and was dated to the Triassic Period – ca. 202 to 253 million years ago.
Within ancient rocks in Arizona’s Petrified Forest National Park, scientists have identified signs of a regular variation in Earth’s orbit that influences climate. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory
The team then linked reversals in Earth’s magnetic field – where the north and south pole shift – to sediments with and without zircons (minerals with uranium that allow for radioactive dating) as well as to climate cycles in the geological record. What these showed was that the 405,000-years cycle is the most regular astronomical pattern linked to Earth’s annual orbit around the Sun.
The results further indicated that the cycle been stable for hundreds of millions of years and is still active today. As Prof. Kent explained, this constitutes the first verifiable evidence that celestial mechanics have played a historic role in natural shifts in Earth’s climate. As Prof. Kent indicated:
“It’s an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago. Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way.”
Previously, astronomers were able to calculate this cycle reliably back to around 50 million years, but found that the problem became too complex prior to this because too many shifting motions came into play. “There are other, shorter, orbital cycles, but when you look into the past, it’s very difficult to know which one you’re dealing with at any one time, because they change over time,” said Prof. Kent. “The beauty of this one is that it stands alone. It doesn’t change. All the other ones move over it.”
The super-continent Pangaea during the Permian period (300 – 250 million years ago). Credit: NAU Geology/Ron Blakey
In addition, scientists were unable to obtain accurate dates as to when Earth’s magnetic field reversed for 30 million years of the Late Triassic – between ca. 201.3 and 237 million years ago. This was a crucial period for the evolution of terrestrial life because it was when the Supercontinent of Pangaea broke up, and also when the dinosaurs and mammals first appeared.
This break-up led to the formation of the Atlantic Ocean as the continents drifted apart and coincided with a mass extinction event by the end of the period that effected the dinosaurs. With this new evidence, geologists, paleontologists and Earth scientists will be able to develop very precise timelines and accurately categorize fossil evidence dated to this period, which show differences and similarities over wide-ranging areas.
This research, and the ability to create accurate geological and climatological timelines that go back over 200 million years, is sure to have drastic implications. Not only will climate studies benefit from it, but also our understanding of how life, and even how our Solar System, evolved. What emerges from this could include a better understanding of how life could emerge in other star systems.
After all, if our search for extra-solar life life comes down to what we know about life on Earth, knowing more about how it evolved here will better the odds of finding it out there.
For decades, scientists have pondered how Earth acquired its only satellite, the Moon. Whereas some have argued that it formed from material lost by Earth due to centrifugal force, or was captured by Earth’s gravity, the most widely accepted theory is that the Moon formed roughly 4.5 billion years ago when a Mars-sized object (named Theia) collided with a proto-Earth (aka. the Giant Impact Hypothesis).
However, since the proto-Earth experienced many giant-impacts, several moons are expected to have formed in orbit around it over time. The question thus arises, what happened to these moons? Raising this very question, a team an international team of scientist conducted a study in which they suggest that these “moonlets” could have eventually crashed back into Earth, leaving only the one we see today.
For the sake of their study, Dr. Malamud and his colleagues – Prof. Hagai B. Perets, Dr. Christoph Schafer and Mr. Christoph Burger (a PhD student) – considered what would happen if Earth, in its earliest form, had experienced multiple giant impacts that predated the collision with Theia. Each of these impacts would have had the potential to form a sub-Lunar mass “moonlet” that would have interacted gravitationally with the proto-Earth, as well as any possible previously-formed moonlets.
Ultimately, this would have resulted in moonlet-moonlet mergers, the moonlets being ejected from Earth’s orbit, or the moonlets falling to Earth. In the end, Dr. Malamud and his colleagues chose to investigate this latter possibility, as it has not been previously explored by scientists. What’s more, this possibility could have a drastic impact on Earth’s geological history and evolution. As Malamud indicated to Universe Today via email:
“In the current understanding of planet formation the late stages of terrestrial planet growth were through many giant collisions between planetary embryos. Such collisions form significant debris disks, which in turn can become moons. As we suggested and emphasized in this and our previous papers, given the rates of such collisions and the evolution of the moons – the existence of multiple moons and their mutual interactions will lead to moonfalls. It is an inherent, inescapable part of the current planet formation theory.”
However, because Earth is a geologically active planet, and because its thick atmosphere leads to natural weathering and erosion, the surface changes drastically with time. As such, it is always difficult to determine the effects of events that happened during the earliest periods of Earth – i.e. the Hadean Eon, which began 4.6 billion years ago with the formation of the Earth and ended 4 billion years ago.
Artist’s conception of asteroids or comets bearing water to a proto-Earth. Credit: Harvard-Smithsonian Center for Astrophysics
To test whether or not multiple impacts could have taken place during this Eon, resulting in moonlets that eventually fell to Earth, the team conducted a series of smooth particle hydrodynamical (SPH) simulations. They also considered a range of moonlet masses, collision impact-angles and initial proto-Earth rotation rates. Basically, if moonlets did fall to Earth in the past, it would have altered the rotation rate of the proto-Earth, resulting in its current sidereal rotation period of 23 hours, 56 minutes, and 4.1 seconds.
In the end, they found evidence that while direct impacts from large objects were not likely that a number of grazing tidal-collisions could have taken place. These would have caused material and debris to be thrown up into the atmosphere that would have formed small moonlets that would have then interacted with each other. As Malamud explained:
“Our results however do show that in the case of a moonfall, the distribution of the material from the moonfall is not even on the Earth, and therefore such collisions can give rise to asymmetries and composition inhomogeneities. As we discuss in the paper, there are actually possible evidence for the latter – moonfalls can potentially explain the isotopic heterogeneities in highly siderophile elements in terrestrial rocks. In principle a moon collisions may also produce a large scale structure on the Earth, and we speculated that such an effect could have contributed to the formation of Earth’s earliest super-continent. This aspect, however, is more speculative, and it is difficult to directly confirm, given the geological evolution of the Earth since those early times.”
This study effectively extends the current and widely-popular Giant Impact Hypothesis. In accordance with this theory, the Moon formed during the first 10 to 100 million years of the Solar System, when the terrestrial planets were still forming. During the final stages of this period, these planets (Mercury, Venus, Earth and Mars) are believed to have grown mainly through impacts with large planetary embryos.
An artist’s depiction of two colliding rocky bodies. Such a collision is the most likely source for the warm dust in the HD 131488 system. Credit: Lynette Cook for Gemini Observatory/AURA
Since that time, the Moon is believed to have evolved due to mutual Earth and Moon tides, migrating outwards to its current location, where it has been ever since. However, this paradigm does not consider impacts that took place before the arrival of Theia and the formation of Earth’s only satellite. As a result, Dr. Malamud and his colleagues assert that it is disconnected from the wider picture of terrestrial planet formation.
By taking into account potential collisions that predate the formation of the Moon, they claim, scientist could have a more complete picture of how both the Earth and the Moon evolved over time. These findings could also have implications when it comes to the study of other Solar planets and moons. As Dr. Malamud indicated, there is already compelling evidence that large-scale collisions affected the evolution of planets and moons.
“On other planets we do see evidence for very large impacts that produced a planet scale topographic features, such as the so-called Mars dichotomy and possibly the dichotomy of Charon’s surface,” he said. “These had to arise from large scale impacts, but small enough as to make sub-global planet features. Moonfalls are natural progenitors of such impacts, but one cannot exclude some other large impacts by asteroids which could produce similar effects.”
There’s also the possibility of such collisions happening in the distant future. According to current estimates of its migration, Mars’ moon Phobos will eventually crash into the surface of the planet. While small compared to the impacts that would have created moonlets and the Moon around Earth, this eventual collision is direct evidence that moonfalls took place in the past and will again in the future.
In short, the history of the early Solar System was violent and cataclysmic, with a great deal of creation resulting from powerful collisions. By having a more complete picture of how these impact events affected the evolution of the terrestrial planets, we may gain new insight into how life-bearing planets formed. This, in turn, could help us track down such planets in extra-solar systems.
Earth’s magnetic field is one of the most mysterious features of our planet. It is also essential to life as we know it, ensuring that our atmosphere is not stripped away by solar wind and shielding life on Earth from harmful radiation. For some time, scientists have theorized that it is the result of a dynamo action in our core, where the liquid outer core revolves around the solid inner core and in the opposite direction of the Earth’s rotation.
In addition, Earth’s magnetic field is affected by other factors, such as magnetized rocks in the crust and the flow of the ocean. For this reason, the European Space Agency’s (ESA) Swarm satellites, which have been continually monitoring Earth’s magnetic field since its deployment, recently began monitoring Earth’s oceans – the first results of which were presented at this year’s European Geosciences Union meeting in Vienna, Austria.
The Swarm mission, which consists of three Earth-observation satellites, was launched in 2013 for the sake of providing high-precision and high-resolution measurements of Earth’s magnetic field. The purpose of this mission is not only to determine how Earth’s magnetic field is generated and changing, but also to allow us to learn more about Earth’s composition and interior processes.
Artist’s impression of the ESA’s Swarm satellites, which are designed to measure the magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere. Credit: ESA/AOES Medialab
Beyond this, another aim of the mission is to increase our knowledge of atmospheric processes and ocean circulation patterns that affect climate and weather. The ocean is also an important subject of study to the Swarm mission because of the small ways in which it contributes to Earth’s magnetic field. Basically, as the ocean’s salty water flows through Earth’s magnetic field, it generates an electric current that induces a magnetic signal.
Because this field is so small, it is extremely difficult to measure. However, the Swarm mission has managed to do just that in remarkable detail. These results, which were presented at the EGU 2018 meeting, were turned into an animation (shown below), which shows how the tidal magnetic signal changes over a 24 hour period.
As you can see, the animation shows temperature changes in the Earth’s oceans over the course of the day, shifting from north to south and ranging from deeper depths to shallower, coastal regions. These changes have a minute effect on Earth’s magnetic field, ranging from 2.5 to -2.5 microtesla. As Nils Olsen, from the Technical University of Denmark, explained in a ESA press release:
“We have used Swarm to measure the magnetic signals of tides from the ocean surface to the seabed, which gives us a truly global picture of how the ocean flows at all depths – and this is new. Since oceans absorb heat from the air, tracking how this heat is being distributed and stored, particularly at depth, is important for understanding our changing climate. In addition, because this tidal magnetic signal also induces a weak magnetic response deep under the seabed, these results will be used to learn more about the electrical properties of Earth’s lithosphere and upper mantle.”
By learning more about Earth’s magnetic field, scientists will able to learn more about Earth’s internal processes, which are essential to life as we know it. This, in turn, will allow us to learn more about the kinds of geological processes that have shaped other planets, as well as determining what other planets could be capable of supporting life.
Be sure to check out this comic that explains how the Swarm mission works, courtesy of the ESA.
Are you ready for a luxury hotel in space? We all knew it was coming, even though it seems impossibly futuristic. But this time it’s not just science fiction; somebody actually has a plan.
The space hotel will be called “Aurora Station” and the company behind it is Orion Span, a Silicon Valley and Houston-based firm. Orion Span aims to deliver the astronaut experience to people, by delivering the people into space. The catch?
“We developed Aurora Station to provide a turnkey destination in space. Upon launch, Aurora Station goes into service immediately, bringing travelers into space quicker and at a lower price point than ever seen before, while still providing an unforgettable experience” – Frank Bunger, CEO and founder of Orion Span.
First of all, a 12 day stay aboard Aurora Station for two people will cost $19 million US, or $9.5 million per person. Even so, you can’t just buy a ticket and hop on board. Guests must also sign up for three months of Orion Span Astronaut Certification (OSAC). Then they’ll be trained at a facility in Houston, Texas.
So once their cheque has cleared, and once they’re trained, what awaits guests on Aurora Station?
Aurora Station will orbit Earth at 320 km (200 m) and will make the trip around Earth every 90 minutes. If you do the math, that’s 16 sunrises and sunsets each day, and guests will enjoy this slideshow for 12 days. Other than this compressed schedule of 96 sunsets and 96 sunrises during their 12 day stay, guests will also be treated to stunning views of the Earth rolling by underneath them, thanks to the unprecedented number of windows Aurora Station will have.
Aurora Station will have 5600 square feet of living space which can be configured as 2 or 4 suites. Image: Orion Span
Aurora Station is the brain-child of Orion Span’s CEO, Frank Bunger. “We developed Aurora Station to provide a turnkey destination in space. Upon launch, Aurora Station goes into service immediately, bringing travelers into space quicker and at a lower price point than ever seen before, while still providing an unforgettable experience,” said Bunger.
Guests won’t be alone on the station, of course. The space hotel will have room for 6 people in total, meaning 4 guests and 2 crew. (You didn’t think you’d be alone up there, did you?) Each pair of guests will still have some alone time though, in what Orion Span calls luxurious private suites for two.
There’s no doubt that staying on a space hotel for 12 days will be the experience of a lifetime, but still, 12 days is a long time. The space station itself will be 5600 square feet, with two suites that can be configured to four. Each suite will be about the size of a small bedroom. Once you’ve gotten used to seeing Earth below you, and you’re used to your suite, what will you do?
Well, there’ll be Wi-Fi of course. So if you’re the type of person who gets bored of orbiting the only planet that we know of that hosts life, and the only planet on which every human civilization has lived and died on, you can always surf the web or watch videos. Aurora Station will also have a virtual-reality holodeck, the cherry-on-top for this science-fiction-come-to- life space resort.
But apparently, boredom won’t be a problem. In an interview with the Globe and Mail, Orion Span CEO Frank Bunger said, ““We talked to previous space tourists, they said 10 days aboard the space station was not enough.” Maybe the extra 2 days in space that Aurora Station guests will enjoy will be just the right amount.
As far as getting guests to the station, that will be up to other private space companies like SpaceX. SpaceX has plans to send tourists on trips around the Moon, and they have experience docking with the International Space Station, so they should be able to transport guests to and from a space hotel.
Aurora Station will also host micro-gravity research and in-situ manufacturing. Image: Orion Span
It doesn’t seem like there’s any shortage of customers. Aurora Station was introduced on April 5th 2018, and the first four months of reservations sold out within 72 hours, with each guest paying a deposit of $80,000 US.
There’s another side to Aurora Station, though. Other than just a nice get-away for people who can afford it, there’s a research aspect to it. Orion Span will offer Aurora Station as a platform for micro-gravity research on a pay-as-you-go basis. It will also lease capacity for in-situ manufacturing and 3D printing research.
But Aurora Station would hardly be in the news if it was only a research endeavour. What’s got people excited is the ability to visit space. And maybe to own some real estate there.
Orion Span is designing Aurora Station to be expandable. They can attach more stations to the original without disrupting anything. And this leads us to Orion Span’s next goal: space condos.
As it says on Orion Span’s website, “Like a city rising from the ground, this unique architecture enables us to build up Aurora Station in orbit dynamically – on the fly – and with no impact to the remainder of Aurora Station. As we add capacity, we will design in condos available for purchase.”
I think we all knew this would happen eventually. If you have the money, you can visit space, and even own a condo there.
Some might say it’s paranoid to think about an asteroid hitting Earth and wiping us out. But the history of life on Earth shows at least 5 major extinctions. And at least one of them, about 65 million years ago, was caused by an asteroid.
Preparing for an asteroid strike, or rather preparing to prevent one, is rational thinking at its finest. Especially now that we can see all the Near Earth Asteroids (NEAs) out there. The chances of any single asteroid striking Earth may be small, but collectively, with over 15,000 NEAs catalogued by NASA, it may be only a matter of time until one comes for us. In fact, space rocks strike Earth every day, but they’re too small to cause any harm. It’s the ones large enough to do serious damage that concern NASA.
NASA has been thinking about the potential for an asteroid strike on Earth for a long time. They even have an office dedicated to it, called the Office of Planetary Defense, and minds there have been putting a lot of thought into detecting hazardous asteroids, and deflecting or destroying any that pose a threat to Earth.
Computer generated simulation of an asteroid strike on the Earth. Credit: Don Davis/AFP/Getty Images
One of NASA’s proposals for dealing with an incoming asteroid is getting a lot of attention right now. It’s called the Hyper-velocity Asteroid Mitigation Mission for Emergency Response, or HAMMER. HAMMER is just a concept right now, but it’s worth talking about. It involves the use of a nuclear weapon to destroy any asteroid heading our way.
The use of a nuclear weapon to destroy or deflect an asteroid seems a little risky at first glance. They’re really a weapon of last resort here on Earth, because of their potential to wreck the biosphere. But out in space, there is no biosphere. If scientists sound a little glib when talking about HAMMER, the reality is they’re not. It makes perfect sense. In fact, it may be the only sensible use for a nuclear weapon.
The idea behind HAMMER is pretty simple; it’s a spacecraft with an 8.8 ton tip. The tip is either a nuclear weapon, or an 8.8 ton kinetic impactor. Once we detect an asteroid on a collision course with Earth, we use space-based and ground-based systems to ascertain its size. If its small enough, then HAMMER will not require the nuclear option. Just striking a small asteroid with sufficient mass will divert it away from Earth.
If the incoming asteroid is larger, or if we don’t detect it early enough, then the nuclear option is chosen. HAMMER would be launched with an atomic warhead on it, and the incoming offender would be destroyed. It sounds like a pretty tidy solution, but it’s a little more complicated than that.
A lot depends on the size of the object and when it’s detected. If we’re threatened by an object we’ve been aware of for a long time, then we might have a pretty good idea of its size, and of its trajectory. In that case, we can likely divert it with a kinetic impactor.
Artist’s impression of the first interstellar asteroid, “Oumuamua”. This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser
But for larger objects, we might require a fleet of impactors already in space, ready to be sent on a collision course. Or we might use the nuclear option. The ER in HAMMER stands for Emergency Response for a reason. If we don’t have enough time to plan or respond, then a system like HAMMER could be built and launched relatively quickly. (In this scenario, relatively quickly means years, not months.)
One of the problems is with the asteroids themselves. They have different orbits and trajectories, and the time to travel to different NEO‘s can vary widely. And things in space aren’t static. We share a region of space with a lot of moving rocks, and their trajectories can change as a result of gravitational interactions with other bodies. Also, as we learned from the arrival of Oumuamua last year, not all threats will be from our own Solar System. Some will take us by surprise. How will we deal with those? Could we deploy HAMMER quickly enough?
Another cautionary factor around using nukes to destroy asteroids is the risk of fracturing them into multiple pieces without destroying them. If an object larger than 1 km in diameter threatened Earth, and we aimed a nuclear warhead at it but didn’t destroy it, what would we do? How would we deal with one or more fragments heading towards Earth?
HAMMER and the whole issue of dealing with threatening asteroids is a complicated business. We’ll have to prepare somehow, and have a plan and systems in place for preventing collisions. But our best bet might lie in better detection.
We’ve gotten a lot better at detecting Near Earth Objects,(NEOs), Potentially Hazardous Objects (PHOs), and Near Earth Asteroids (NEAs) lately. We have telescopes and projects dedicated to cataloguing them, like Pan-STARRS, which discovered Oumuamua. And in the next few years, the Large Synoptic Survey Telescope (LSST) will come online, boosting our detection capabilities even further.
It’s not just extinctions that we need to worry about. Asteroids also have the potential to cause massive climate change, disrupt our geopolitical order, and generally de-stabilize everything going on down here on Earth. At some point in time, an object capable of causing massive damage will speed toward us, and we’ll either need HAMMER, or another system like it, to protect ourselves and the planet.
