An artist's illustration of the MOM orbiter at Mars. Image: By Nesnad - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=29435816
Science—like literature and the arts—helps nations cooperate together, even when they’re in conflict politically. The USA and Russia are in conflict over the Ukraine and Syria, yet both nations still cooperate when it comes to the International Space Station. With that in mind, it’s great to see other nations—in this case India—taking on a greater role in space exploration and sharing their scientific results.
India’s Mars Orbiter Mission (MOM) probe has been in orbit around Mars since September 2014, after being launched in November 2013. Though the Indian Space Research Organization (ISRO) has released plenty of pictures of the surface of Mars, they haven’t released any scientific data. Until now.
A beautiful full-disc image of Mars captured by MOM. Image: ISRO/MOM.
In September 2015, MOM’s orbit was adjusted to bring it to within 260 km of Mars’ surface, significantly closer to the surface than the usual 400 km altitude. This manoeuver allowed one of MOM’s six instruments, the Mars Exospheric Neutral Composition Analyzer (MENCA), to measure the atmospheric composition at different altitudes. The sensor measured carbon dioxide, oxygen, nitrogen and carbon monoxide to see how they were distributed at different altitudes.
MOM’s activity at Mars is important for a couple of reasons. Its results confirm the results of other probes that have studied Mars’ atmosphere. And confirmation is an important part of science. But there’s another reason why MOM is important, and this centres around the search for evidence of life on the Red Planet.
Methane is considered a marker for the presence of life. It’s not an absolute indicator that life is or was present, but it’s a good hint. One of MOM’s sensors is the Methane Sensor for Mars (MSM.) Methane has been detected in Mars’ atmosphere before, but these could have been spikes, and not a strong indicator of living processes. If MSM provides stronger data indicating a consistent methane presence, that would be very interesting.
Releasing these results is also vindication for ISRO. In 2008, ISRO released data from their lunar mission, Chandrayaan-1, showing the presence of water on the Moon. Those results, which were gathered with an instrument called Chandra’s Altitudinal Composition Explorer (CHACE) were rejected by several scientific publications, on the grounds that the results were contaminated. Only when they were confirmed by another of Chandrayaan-1’s instruments—the Moon Mineralogy Mapper (M3)—were the results accepted.
But MOM’s MENCA instrument is based on the CHACE instrument aboard Chandrayaan-1, so ISRO feels that MENCA’s success in the atmosphere at Mars vindicates CHACE’s results on the Moon. And rightly so.
You can read a blog post by Syed Maqbool Ahmed at the Planetary Society, where he talks about the success of MOM’s MENCA, and how it vindicates ISRO’s earlier results with CHACE that showed the presence of water on the Moon.
MOM is India’s first interplanetary mission, and is expected to last until its fuel runs out, which could take many years. India is the first Asian nation to make it to another planet, and the first of any nation to make it to Mars on their first attempt. Not bad for a mission that was initially considered to be only a technology demonstration mission.
A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University
“What happened to Mars?” is one of the most compelling questions in space science. It probably wasn’t always the dead, dry, cold place it is now. Did its core cool and stop rotating, allowing the full glare of the sun to blast away its atmosphere and water, and kill anything that may have lived there? Was it struck by a large body, which incinerated its atmosphere, and led to its demise? Were there other causes?
According to a new research paper from Sylvain Bouley at the University of Paris-South, and his colleagues, it may have been a massive, ancient outpouring of molten rock that threw Mars off kilter and helped change Mars into what it is today.
The Tharsis region is an ancient lava complex on Mars that dates back to between 4.1 billion and 3.7 billion years ago. It’s located in Mars’ Western Hemisphere, right near the equator. It’s made up of three huge shield volcanoes—Arsia Mons, Pavonis Mons, and Ascraeus Mons. Collectively, they’re known as Tharsis Montes. (Olympus Mons, the largest volcano in the Solar System, is not a part of the Tharsis complex, though it is near it.)
Tharsis is over 5,000 km across and over 10 miles thick, making it the largest volcanic complex in the Solar System. That much mass positioned after Mars was already formed and had an established rotation would have been cataclysmic. Think what would happen to Earth if Australia rose up 10 miles.
An image of the Syria-Thaumasia region of the Tharsis complex, showing the volcano Arsia Mons on the left, and Valles Marineris on the northern edge. Brown areas are the highest altitude. Open Source Image: Arizona State University, JMars.
The new paper, published on March 2nd, 2016, in the journal Nature, says that the position of the Tharsis complex would have initiated a True Polar Wander (TPW.) Basically, what this means is that Tharsis’ huge mass would have forced Mars to shift its rotation, so that the location of Tharsis became the new equator.
It was thought that the emergence of Tharsis made Martian rivers—which formed later—flow the direction they do. But the study from Bouley and his colleagues shows that Martian rivers and valleys formed first—or maybe concurrently—and that the Tharsis TPW deformed the planet later.
The authors of the study calculated where the Martian poles would have been prior to Tharsis, and looked for evidence of polar conditions at those locations. The location of this ancient north pole contains a lot of ice today, and the location of the ancient south polar region also shows evidence of water.
What it all adds up to is that the disappearance of water on Mars probably happened at the same time as the TPW. Whether the appearance of the Tharsis lava complex, and the resulting cataclysmic shifting of Mars’ rotational orientation, were the cause of Mars losing its climate is not yet known for sure. But this study shows that the ancient volcanic cataclysm did at least help shape Mars into what it is today.
The view from the beach on Titan? A recent study has shown that Titan's seas experience very low waves, making it a perfect place for a probe to set down.Credit: NASA
Space is mostly vast and empty. So whenever we notice something like ripples on a lake, on the frozen moon of a gas giant, we take notice.
At a meeting of the American Geophysical Union in San Francisco this week, it was reported that Cassini images of Saturn’s moon Titan showed light being reflected from the Ligeia Mare, a frigid sea of hydrocarbons on that moon. Subsequent images showed the same phenomenon on two other seas of Titan, as well. These are thought to be waves, the first waves detected anywhere other than Earth, and suggest that Titan has more geophysical activity than previously thought.
Surfers on Earth, known for seeking out remote and secretive locations, shouldn’t get too excited. According to mathematical modelling and radar imagery, these waves are only 1.5 cm (0.6 inches) tall, and they’re moving only 0.7 metres (2.3 feet) per second. Plus, they’re on a sea of liquid hydrocarbons—mostly methane—that is a frigid -180 degrees Celsius (-292 F.)
The left image shows a mosaic of images of Titan taken by the Cassini spacecraft in near infrared light. Titan’s polar seas are visible as sunlight glints off of them. The right image is a radar image of Kraken Mare. Credit: NASA Jet Propulsion Laboratory.
Planetary scientists are taking note, though, because these waves show that Titan has an active environment, rather than just being a moon frozen in time. It’s thought that the change in seasons on Titan is responsible for these waves, as Titan begins its 7 year summer. Processes related to the changing seasons on Titan have created winds, which have cause these ripples.
There’s other evidence of active weather on Titan, including dunes, river channels, and shorelines. But this is the first observation of active weather phenomena, rather than just the results. All together, it shows that Titan is a more active, dynamic environment than previously thought.
Titan’s hydrocarbon lakes are thought to be up to 200 metres (656 ft.) deep, and are clustered around the north polar region. Just one of its lakes is thought to contain approximately 9,000 cubic km of methane, which is about 40 times more than the Earth’s reserves of oil and gas.
Titan is the second largest moon in the Solar System, second only to Ganymede, and both moons are larger than the planet Mercury. Titan was discovered in 1655 by Christiaan Huygens.
The planet Venus, as imaged by the Magellan 10 mission. The planet's inhospitable surface makes exploration extremely difficult. Credit: NASA/JPL
The first spacecraft to reach the surface of another world was the Soviet Venera 3 probe. Venera 3 crash-landed on the surface of Venus on March 1, 1966, 50 years ago. It was the 3rd in the series of Venera probes, but the first two never made it.
Venera 3 didn’t last long. It survived Venus’ blistering heat and crushing atmospheric pressure for only 57 minutes. But because of that 57 minutes, its place in history is cemented.
With a temperature of 462 degree C. (863 F.,) and a surface pressure 90 times greater than Earth’s, Venus’ atmosphere is the most hostile one in the Solar System. But Venus is still a tantalizing target for exploration, and rather than letting the difficult conditions deter them, Venus is a target that NASA thinks it can hit.
The Venus Landsail—called Zephyr—could be the first craft to survive the hostile environment on Venus. If approved, it would launch in 2023, and spend 50 days on the surface of Venus. But to do so, it has to meet several challenges.
NASA thinks they have the electronics that can withstand the heat, pressure, and corrosive atmosphere of Venus. Their development of sensors that can function inside jet engines proves this, and is the kind of breakthrough that really helps to advance space exploration. They also have solar cells that should function on the surface of Venus.
But the thick cloud cover will prevent the Zephyr’s solar cells from generating much electricity; certainly not enough for mobility. They needed another solution for traversing the surface of Venus: the land sail.
An artist’s conception of what NASA’s Zephyr Landsail might look like on the surface of Venus. Image: NASA Glenn Research Center.
Venus has very slow winds—less than one meter per second—but the high density of the atmosphere means that even a slow wind will allow Zephyr to move effectively around the Venusian surface. But a land sail will only work on a surface without large rocks in the way. Thanks to the images of the surface of Venus sent back to Earth from the Venera probes, we know that a land sail will work, at least in some parts of the Venusian surface.
So Venus is back on the menu. With all the missions to other places in the Solar System, Venus is kind of forgotten, right here in our own backyard. But there’s actually a pretty rich history of missions to Venus, even though an extended visit to the surface has been out of reach. Since it’s been 50 years since Venera 3 reached the surface, now is a good time to look back at the history of the exploration of Venus.
The Soviet Union dominated the exploration of Venus. The Venera probes went all the way up to Venera 16, though some were orbiters rather than landers. From one perspective, the whole Venera program was plagued with problems. Many of the craft failed completely, or else had malfunctions that crippled them. But they still returned important information, and achieved many firsts, so the Venera program overall has to be considered a success.
The Soviet Union did not like to acknowledge or talk about space missions that failed. They often changed the name of a mission if it failed, so the names and numbers can get a little confusing.
Venera 4 was actually the first spacecraft to transmit any data from another world. On October 18th, 1967, it transmitted data from Venus’ atmosphere, but none from the surface. There were actually ten Venera missions before it, but most of them didn’t make it to Venus, suffering explosions or failing to leave Earth’s orbit and crashing back to the surface of Earth. Two of the Venera probes, numbers 1 and 2, suffered a loss of communications, so their fate is unknown.
After Venera 4’s relative success, there was another failed craft that fell back to Earth. Then on May 16th, 1969, Venera 5 successfully entered Venus’ atmosphere, and made it to within 26 kilometers of the surface before being crushed by the pressure. The next day—the Soviets often launched missions in pairs—Venera 6 entered the atmosphere of Venus and successfully transmitted data. It made it deeper into the atmosphere before being crushed within 11 kilometers of the surface.
Venera 7 was a successful mission. On December 15th, 1970, it landed on the surface of Venus and survived for 23 minutes. Venera 7 was the very first broadcast from the surface of another planet.
In 1972 Venera 8 survived for 50 minutes on the surface, followed by Venera 9 in 1975. Venera 9 survived for 53 minutes and sent back the first black and white images of the surface of Venus. Venera 10 landed 3 days after Venera 9 and survived 65 minutes, and also sent photos back. Grainy and blurry, but still amazing!
Images from Venera 9 (top) and Venera 10 (bottom). Public Domain Images, courtesy of NASA/National Space Science Data Center.
December 1978 saw the arrival of Venera 11 and 12, surviving 95 and 112 minutes respectively. Venera 11’s camera failed, but Venera 12 recorded what is thought to be lightning.
In March 1982, Venera 13 and 14 arrived. 13 took the first color images of the surface of Venus, and both craft took soil samples. Venera 15 and 16—both orbiters—arrived in 1983 and mapped the northern hemisphere.
The first color pictures taken of the surface of Venus by the Venera-13 space probe. Credit: NASA
The Soviet Unions final missions to Venus were Vega 1 and Vega 2, in 1985, which combined landings on Venus and flybys of Halley’s comet into each mission. Vega 1’s surface experiments failed, while Vega 2 transmitted data from the surface for 56 minutes.
The United States has also launched several mission to Venus, though none have been landers. Spacecraft in the Mariner series studied Venus from orbit and during flybys, sometimes getting quite close to the cloud tops.
In 1962 and 1967, Mariner 2 and 5 completed flybys of Venus and transmitted data back to Earth. Mariner 5 came as close as 4094 km of the surface. In February 1974, Mariner 10 approached Venus and came to within 5,768 km. It returned color images of Venus, and then used gravitational assist—the first spacecraft to ever do so—to propel itself to Mercury.
Mariner 10’s Venus. Image: NASA
In December 1978, the Pioneer Venus Orbiter reached Venus and studied the atmosphere, surface, and other aspects of Venus. It lasted until August 1992, when its fuel ran out and it was destroyed when it entered the atmosphere.
On August 1990, the Magellan mission reached Venus and used radar to map the surface of the planet. On October 1994, Magellan entered the Venusian atmosphere and was destroyed, but not before successfully mapping over 99% of the planet’s surface.
Deployment of Magellan with Inertial Upper Stage booster. Credit: NASA
Messenger was a NASA mission to Mercury that was launched in August 2004. It did two flybys of Venus, in October 2006 and June 2007.
The Venus Express, a European Space Agency mission, orbited Venus and studied the atmosphere and plasma of Venus. Of special interest to Venus Express was the study of what role greenhouse gases played in the formation of the atmosphere.
In 2010, the Japanese Space Agency launched Akatsuki, also known as the Venus Climate Orbiter. It’s role is to orbit Venus and study the atmospheric dynamics. It will also look for evidence of lightning and volcanic activity.
If there’s one thing that space exploration keeps teaching us, it’s to expect the unexpected. Who knows what we’ll find on Venus, if the Land Sail mission is approved, and it survives for its projected 50 days.
Scott Kelly of NASA captured this image, from aboard the International Space Station, of the Soyuz TMA-17M leaving the ISS on Dec. 11, 2015. Credits: NASA/Scott Kelly
American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko will return to Earth tonight after 340 days aboard the International Space Station. The year in space may have been fairly routine in some aspects (other than goofing around in a gorilla suit,) but the return to Earth aboard the Soyuz capsule will be anything but.
After un-docking from the ISS at 8:02 pm EST, the Soyuz—piloted by commander Sergey Volkov—will move about 12 miles away. Then the Soyuz’s braking rockets will be fired for 4 minutes and 49 seconds, slowing the craft by 460 kmh (286 mph.) Then begins the harrowing part.
An illustration of the Soyuz with the descent module highlighted. Image: NASA.
Soyuz will free-fall for 25 minutes, until it hits the Earth’s atmosphere at 100 km (62 miles) above the surface. Then the craft has to withstand a five-minute stretch of extreme heating as it descends to 20 miles above the Earth’s surface. At an altitude of 10.6 km (6.6 miles), a large parachute—called a drogue chute—will deploy from Soyuz’s descent module, helping to slow the craft’s descent. Lastly, rockets will fire, which will lead to a jarring and nerve-wracking touchdown in Kazakhstan. According to Kelly, who has two space shuttle flights to his credit, the whole experience defies description.
Inside Soyuz: Expedition 45 crew members Kjell Lindgren of NASA, Oleg Kononenko of the Russian Federal Space Agency and Kimiya Yui of the Japan Aerospace Exploration Agency settle into the Soyuz TMA-17M spacecraft that carried them safely back to Earth on Dec. 11, 2015. Credits: NASA
But it’s what happens when Kelly is back on Earth that is the most important part of this record-breaking 340 day mission aboard the ISS. It’s no coincidence that the mission was exactly 340 days long. That’s how long a manned mission to Mars is expected to take, and Kelly’s and Kornienko’s mission was designed to mimic that. NASA hopes to gain an understanding of the effects a Mars mission will have on the astronauts who make that trip.
What’s unique about Kelly is that he has a twin brother Mark—also an astronaut and former shuttle commander—who is being monitored and subjected to the same tests as Scott during his year in space. By comparing the twin brothers before, during, and after Scott’s year aboard the ISS, NASA expects to learn a lot about extended periods of weightlessness and long-term exposure to radiation, and how astronauts will be affected. And that will all happen as soon as Kelly and Kornienko return.
Any crew member returning from space faces a battery of tests to determine their condition. But Kelly and Kornienko will face all that and then some. It’s essential that the two are assessed as soon as they return, because their bodies will begin to acclimatize to Earth’s gravity as soon as they land. After exiting Soyuz, they will be transported directly to medical tents, where they will sit in recliners. They will have a short time to get their bearings, then testing will begin. For Kelly, the testing will continue on his flight back to the USA. The more detail they can gather on Kelly’s condition and physiology, the better it will be for any astronauts making the trip to Mars in the future.
This is important, ground-breaking stuff. And with missions like this, NASA and other organizations are learning a lot and are continuing to expand humanity’s horizons. But, as we keep seeing, there is always a lighter side to these endeavours: For fun, check out NASA’s Crazy Facts About The Year In Space.
An illustration of what a quiet supersonic passenger aircraft might look like. Image: Lockheed Martin.
NASA has plans to develop new supersonic passenger aircraft that are not only quieter, but also greener and less expensive to operate. If NASA’s 2017 budget is approved, the agency will re-start their X-Plane program, the same program which was responsible for the first supersonic flight almost 70 years ago. And if all goes according to plan, the first test-model could be flying as soon as 2020.
The problem with supersonic flight—and the reason it’s banned— is the uber-loud boom that it creates. When an aircraft passes the speed of sound, a shockwave is created in the air it passes through. This shockwave can travel up to 40 kilometres (25 miles), and can even break windows. NASA thinks new aircraft designs can prevent this, and it starts with abandoning the ‘tube and wings’ model that current passenger aircraft design adheres to. It’s hoped that new designs will avoid the sonic booms that cause so much disturbance, and instead produce more of a soft thump, or supersonic ‘heartbeat.’
Another illustration of what a quiet supersonic aircraft might look like. Image: NASA/Boeing.
The image above shows what a hybrid wing-body aircraft might look like. Rather than a tube with wings attached, this design uses a unified body and wings built together. It’s powered by turbofan engines, and has vertical fins on the rear to direct sound up and away from the ground. (Just don’t ask for a window seat.)
Lockheed Martin Aeronautics has been chosen to complete a preliminary design for Quiet Supersonic Technology (QueSST.) They will have about 17 months to produce a design, which will then lead to a more detailed designing, building, and testing of a new QueSST jet, about half the size of a production aircraft. This aircraft will then have to undergo analytical testing and wind-tunnel validation.
After the design and build of QueSST will come the Low Boom Flight Demonstration (LBFD) phase. During the LBFD phase, NASA will seek community input on the aircraft’s performance and noise factor.
But noise reduction is not the only goal of NASA’s new X-Plane program. NASA administrator Charles Bolden acknowledged this when he said, “NASA is working hard to make flight greener, safer and quieter—all while developing aircraft that travel faster, and building an aviation system that operates more efficiently.”
NASA has been working in recent years to reduce aircraft fuel consumption by 15%, and engine nitrogen oxide emissions by 75%. These goals are part of their Environmentally Responsible Aviation (ERA) project, which began in 2009. Other goals of ERA include reducing aircraft drag by 8% and aircraft weight by 10%. These goals dovetail nicely with their revamped X-Plane initiative.
It’s hard to bet against NASA. They’re one of the most effective organizations on Earth, and when they set goals, they tend to meet them. If their X-Plane program can achieve its goals, it will be a win for aircraft design, for paying customers, and for the environment.
For a look at the history of the X-Plane project, look here.
Astronaut Scott Kelly in a gorilla suit, courtesy of his brother Mark. Image: Scott Kelly
It seems that besides doing a lot of important science, and generally expanding humanity’s horizons, astronaut Scott Kelly has time for a practical joke. Thanks to his twin brother Mark, Scott received a gorilla costume when the ISS was resupplied, and used it to chase his crew-mate Tim Peake around. It’s a funny but effective way to celebrate a year in space.
Interstellar travel will require near-light-speed to be feasible. Image: NASA
We’ve achieved amazing things by using chemical rockets to place satellites in orbit, land people on the Moon, and place rovers on the surface of Mars. We’ve even used ion drives to reach destinations further afield in our Solar System. But reaching other stars, or reducing our travel time to Mars or other planets, will require another method of travel. One that can approach relativistic speeds.
Your aim has to be really really good. Credit: UCSB Experimental Cosmology GroupWe can execute missions to Mars, but it takes several months for a vehicle to reach the Red Planet. Even then, those missions have to be launched during the most optimal launch windows, which only occur every 2 years. But the minds at NASA never stop thinking about this problem, and now Dr. Philip Lubin, Physics Professor at the University of California, Santa Barbara, may have come up with something: photonic propulsion, which he thinks could reduce the travel time from Earth to Mars to just 3 days, for a 100 kg craft.
The system is called DEEP IN, or Directed Propulsion for Interstellar Exploration. The general idea is that we have achieved relativistic speeds in the laboratory, but haven’t taken that technology—which is electromagnetic in nature, rather than chemical—and used it outside of the laboratory. In short, we can propel individual particles to near light speed inside particle accelerators, but haven’t expanded that technology to the macro level.
Directed Energy Propulsion differs from rocket technology in a fundamental way: the propulsion system stays at home, and the craft doesn’t carry any fuel or propellant. Instead, the craft would carry a system of reflectors, which would be struck with an aimed stream of photons, propelling the craft forward. And the whole system is modular and scalable.
Photonic propulsion explained.
If that’s not tantalizing enough, the system can also be used to deflect hazardous space debris, and to detect other technological civilizations. As talked about in this paper, detecting these types of systems in use by other civilizations may be our best hope for discovering those civilizations.
There’s a roadmap for using this system, and it starts small. At first, DEEP IN would be used to launch small cube satellites. The feedback from this phase would then inform the next step, which would be to test a unit for defending the ISS from space debris. From then, the systems would meet goals of increasing complexity, from launching satellites to LEO (Low-Earth Orbit) and GEO (Geostationary Orbit), all the way up to asteroid deflection and planetary defense. After that, relativistic drives capable of interstellar travel is the goal.
There are lots of questions still to be answered of course, like what happens when a vehicle at near light-speed hits a tiny meteorite. But those questions will be asked and answered as the system is developed and its capabilities grow.
Obviously, DEEP IN has the potential to bring other stars into reach. This system could deliver probes to some of the more promising exo-planets, and give humanity its first detailed look at other solar systems. If DEEP IN can be successfully scaled up, as Lubin says, then it will be a transformational technology.
Artists concept of a shredded asteroid getting too close to a star. (NASA/JPL-Caltech)
The Sun has enormous destructive power. Any objects that collide with the Sun, such as comets and asteroids, are immediately destroyed.
But now we’re finding that the Sun has the ability to reach out and touch asteroids at a far greater distance than previously thought. The proof of this came when a team at the University of Hawaii Institute of Astronomy was looking at Near-Earth Objects (NEOs) catalogued by the Catalina Sky Survey, and trying to understand what asteroids might be missing from that survey.
An asteroid is classified as an NEO when, at its closest point to the Sun, it is less than 1.3 times the distance from the Earth to the Sun. We need to know where these objects are, how many of them there are, and how big they are. They’re a potential threat to spacecraft, and to Earth itself.
The 60 inch Mt. Lemmon telescope is one of three telescopes used in the Catalina Sky Survey. Image: Catalina Sky Survey, University of Arizona.
The Catalina Sky Survey (CSS) detected over 9,000 NEOs in eight years. But asteroids are notoriously difficult to detect. They are tiny points of light, and they’re moving. The team knew that there was no way the CSS could have detected all NEOs, so Dr. Robert Jedicke, a team member from the University of Hawaii Institute of Astronomy, developed software that would tell them what CSS had missed in its survey of NEOs.
This took an enormous amount of work—and computing power—and when it was completed, they noticed a discrepancy: according to their work, there should be over ten times as many objects within ten solar diameters of the Sun as they found. The team had a puzzle on their hands.
The team spent a year verifying their work before concluding that the problem did not lay in their analysis, but in our understanding of how the Solar System works. University of Helsinki scientist Mikael Granvik, lead author of the Nature article that reported these results, hypothesized that their model of the NEO population would better suit their results if asteroids were destroyed at a much greater distance from the sun than previously thought.
They tested this idea, and found that it agreed with their model and with the observed population of NEOs, once asteroids that spent too much time within 10 solar diameters of the Sun were eliminated. “The discovery that asteroids must be breaking up when they approach too close to the Sun was surprising and that’s why we spent so much time verifying our calculations,” commented Dr. Jedicke.
There are other discrepancies in our Solar System between what is observed and what is predicted when it comes to the distribution of small objects. Meteors are small pieces of dust that come from asteroids, and when they enter our atmosphere they burn up and make star-gazing all the more eventful. Meteors exist in streams that come from their parent objects. The problems is, most of the time the streams can’t be matched with their parent object. This study shows that the parent objects must have been destroyed when they got too close to the Sun, leaving behind a stream of meteors, but no apparent source.
There was another surprise in store for the team. Darker asteroids are destroyed at a greater distance from the Sun than lighter ones are. This explains an earlier discovery, which showed that brighter NEOs travel closer to the Sun than darker ones do. If darker asteroids are destroyed at a greater distance from the Sun than their lighter counterparts, then the two must have differing compositions and internal structure.
“Perhaps the most intriguing outcome of this study is that it is now possible to test models of asteroid interiors simply by keeping track of their orbits and sizes. This is truly remarkable and was completely unexpected when we first started constructing the new NEO model,” says Granvik.
An artist's impression of a Gamma Ray Burst. Credit: Stanford.edu
Last week’s announcement that Gravitational Waves (GW) have been detected for the first time—as a result of the merger of two black holes—is huge news. But now a Gamma Ray Burst (GRB) originating from the same place, and that arrived at Earth 0.4 seconds after the GW, is making news. Isolated black holes aren’t supposed to create GRB’s; they need to be near a large amount of matter to do that.
NASA’s Fermi telescope detected the GRB, coming from the same point as the GW, a mere 0.4 seconds after the waves arrived. Though we can’t be absolutely certain that the two phenomena are from the same black hole merger, the Fermi team calculates the odds of that being a coincidence at only 0.0022%. That’s a pretty solid correlation.
So what’s going on here? To back up a little, let’s look at what we thought was happening when LIGO detected gravitational waves.
Our understanding was that the two black holes orbited each other for a long time. As they did so, their massive gravity would have cleared the area around them of matter. By they time they finished circling each other and merged, they would have been isolated in space. But now that a GRB has been detected, we need some way to account for it. We need more matter to be present.
According to Abraham Loeb, of Harvard University, the missing piece of this puzzle is a massive star—itself the result of a binary star system combining into one—a few hundred times larger than the Sun, that spawned two black holes. A star this size would form a black hole when it exhausted its fuel and collapsed. But why would there be two black holes?
Again, according to Loeb, if the star was rotating at a high enough rate—just below its break up frequency—the star could actually form two collapsing cores in a dumbbell configuration, and hence two black holes. But now these two black holes would not be isolated in space, they would actually be inside a massive star. Or what was left of one. The remnants of the massive star is the missing matter.
When the black holes joined together, an outflow would be generated, which would produce the GRB. Or else the GRB came “from a jet originating out of the accretion disk of residual debris around the BH remnant,” according to Loeb’s paper. So why the 0.4 s delay? This is the time it took the GRB to cross the star, relative to the gravitational waves.
It sounds like a nice tidy explanation. But, as Loeb notes, there are some problems with it. The main question is, why was the GRB so weak, or dim? Loeb’s paper says that “observed GRB may be just one spike in a longer and weaker transient below the GBM detection threshold.”
But was the GRB really weak? Or was it even real? The European Space Agency has their own gamma ray detecting spacecraft, called Integral. Integral was not able to confirm the GRB signal, and according to this paper, the gamma ray signal was not real after all.
