A really interesting set of images taken by NASA’s Mars Reconnaissance Orbiter was announced this past week. Here’s one of Newton Crater taken from orbit and edited with 3D modeling1 to better show the slopes at the edge of the crater. The most interesting and relevant parts of the picture are the dark lines appearing on the surface.
What makes these dark features really intriguing is that they are seasonal. They begin to appear and then extend down slope in spring and into the summer. Then in winter, they disappear completely, to return again the following spring. The best explanations that the researchers have been able to offer for this discovery is the flow of briny water. If true, this will be the first instance that we have found liquid water on Mars2.
The flows are on the order of just a few meters wide and occur on the brighter slopes, where there is more sunlight. The locations and temperatures of these features reduced the possibilities of what they could be. This could have indicated the presence of carbon dioxide frost, but the sites where the flows were found were simply too warm. The presence of pure liquid water was ruled out as well, since temperatures at most sites were too low for water to exist as a liquid. This led to strong evidence for liquid brine: the presence of salt in the water would lower its freezing temperature, allowing it to flow.
Yet, the dark lines appearing on the surface were not occurring because it was getting wet. Spectrometers onboard the orbiter could not find any signs of water on the surface below. This suggests that the darkness must be appearing for some other reasons. A possibility suggested by researchers is that the flow of water may be under the surface and could be altering the way grains on the surface are reflecting light, making the area appear darker. There still are no strong models as to what process is exactly making the surface darker and why the areas regain their brightness during the winter.
Of course, this news is exciting for those who are keen on finding traces of life on Mars. For me, though, the research is much more intriguing because of the implications it has about Mars as a planet. Finding flowing water on Mars, among the other great discoveries made recently, have painted the red planet to be much more different and interesting than I had ever imagined. Certainly, the presence of life would be exciting, but I find it no less exciting to see Mars have liquid water and the implications that has for other similar planets found outside our Solar System.
And like most images released to the public by NASA, the color has also been “enhanced”. ↩
There has been strong evidence for the presence of water on Mars, with frozen water located in Polar regions, and perhaps even flowing water in Mars’ history. This discovery lends evidence towards liquid water on Mars right now. ↩
“You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, ‘Look at that, you son of a bitch.’”—Edgar Mitchell, Apollo 14 Astronaut
NASA’s Dawn Spacecraft is now in orbit around the asteroid Vesta. Late Friday night, Dawn became the first spacecraft to enter orbit around an object in the asteroid belt.
Vesta was the fourth asteroid to be discovered, with an average diameter of 530 kilometers and the title of being the second most massive asteroid known. From the Earth, it is also the brightest asteroid viewable, and therefore it has long been the target of several observations conducted by ground and space based telescopes. Yet, as powerful as these tools may be, details on the surface could never be resolved easily. The Dawn spacecraft’s job is to help solve this problem. By studying the asteroid in close detail, a better record can be revealed of not only Vesta’s rich past, but also that of the entire Solar System as well. Other scientific tasks, such as more precisely measuring the mass of the asteroid by studying the gravitational pull on the spacecraft, will begin in August.
This morning, the first close-up images of Vesta ever taken were released. A stunning amount of detail is revealed. Just compare the following images of Vesta, the first one taken by the Hubble Space Telescope, and the second one by Dawn.
Also if you have red-green or red-blue glasses, you can view the following 3-D image composed of two separate images taken by Dawn’s framing camera instrument.
While entering orbit around Vesta, Dawn made another accomplishment by achieving the largest propulsive acceleration carried out by any spacecraft (more than 6.7 km/s2). This was accomplished by its ion engines that provide thrust by expelling ions.
Image Credits: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA, ESA
In a country where some corporations do not pay taxes, millionaires get farm subsidies and a presidential candidate can run up a half-million-dollar tab at Tiffany’s, we’re deferring an attempt to answer one of our most enduring (and least inexpensive to answer) questions: Are we alone in the universe?
I watched the last shuttle launch using my iPhone. Combining my Twitter feed with the live NASA TV stream of the launch gave a truly unique experience. Not only was I getting a great view of the launch, but I could also quickly switch to live incoming bits of information from people who had a much better idea on what was actually taking place down in Florida. This was in many ways invaluable, and I somewhat regret not doing this for other previous launches.
Below are some screenshots of my “setup”.
The last one was taken right after external tank separation.
In much the same way as seismologists use earthquakes to study the Earth’s interior and moonquakes to study the Moon’s interior, astronomers use seismic quakes on astronomical bodies to learn about their structure. Helioseismologists look at seismic waves on the Sun, while asteroseismology extends these techniques to other stars. However, the waves astronomers study are different than those on Earth. Terrestrial quakes are disturbances tens to hundreds of kilometers into the Earth, most commonly due to energy release along tectonic plates, that propagate to the surface. Starquakes are thought to be the result of turbulence in the convective zone and cause the entire star to ring like a bell.
In this paper, techniques from asteroseismology are applied to yet another object: Jupiter.
Researchers studying the oxygen of Genesis samples found that the percentage of O-16 in the sun is slightly higher than on Earth, the moon, and meteorites. The other isotopes’ percentages were slightly lower. […] “The implication is that we did not form out of the same solar nebula materials that created the sun — just how and why remains to be discovered,” said Kevin McKeegan, a Genesis co-investigator from the University of California, Los Angeles and the lead author of one of two Science papers published this week.
Until the early 1920s, the size scale of the universe was not confirmed. Some astronomers believed that the Milky Way was the total universe. They argued that if other nebulae seen in the sky, like Andromeda, were in fact individual galaxies like our own, then they must be at a distance on the order of 108 light years, a simply incomprehensible distance scale that many were reluctant to accept. Leading this side of the argument was Harlow Shapley, who cited several pieces of evidence. Adrian van Maanen made the claim that he observed the Pinwheel nebula to be rotating. The implication was that if the Pinwheel was in fact a galaxy, the velocities would be simply too enormous: at that scale, they would easily exceed the speed of light which would be impossible. Shapley also cited the observation of a nova in Andromeda, which had gotten brighter than the entire nebula itself. The fact that a nova could get brighter than an entire galaxy seemed absurd.
Others believed that nebulae like the Andromeda were in fact separate galaxies, or as they were called at the time, “island universes”. Representing this side of the debate was Heber Curtis, who made claims such as the dark lanes visible in other nebulae were similar to the dust clouds present in the Milky Way.1
Ultimately, what settled the debate was just one humble star, discovered by Edwin Hubble at Mount Wilson Observatory. What made this star, now called V1, special, and ultimately so useful was the fact that it was a Cepheid variable stars.
About 16 years previously, while investigating variable stars in the Magellanic Clouds, Henrietta Swan Leavitt made the discovery of a relationship between the period and luminosity of Cepheid variables. That is, she realized that there was a strong relationship between the timescale that the star pulsated at and its brightness. This had a huge consequences for measuring astronomical distances. Simply finding the pulsation period of this kind of star gave its true brightness by the relationship, and since farther objects appear dimmer, the distance to the star could be easily calculated. Hubble knew about this relationship, and upon realizing that the star he observed was a Cepheid variable, he excitedly labeled the object “VAR!”2 since it would have monumental implications for the debate about “island universes”. Hubble would proceed to find 11 more Cepheid variables, among the variable stars he was discovering in Andromeda.
Initially, Hubble calculated the distance to Andromeda to be 285 kpc, significantly smaller than the modern value of 770 kpc3. Still, this was more than enough to show that these nebulae were in fact island universes. In one clean demonstration, Hubble used V1 to dramatically increase the size of the universe as we understood it. No longer was our understanding of the scale of the universe confined to just the size of the Milky Way, but instead was a great deal larger, and more complex, than we could easily comprehend or even imagine.
Recently, the Hubble Space Telescope had performed observations of the same star used famously by its namesake. Images from the observations have been released, and a few are shown below.
Image and Illustration Credits: Mount Wilson Observatory Historical Archive, NASA, ESA, Z. Levay (STScl), and the Hubble Heritage Team (STScl/AURA)
The two, Shapley and Curtis, took part in a very prominent debate at the Smithsonian Museum of Natural History on April 26, 1920, called the Great Debate. Both their arguments had flaws that were later realized. The Pinwheel nebula was not in fact observed to be rotating. The nova observed in Andromeda was really a supernova, which can in fact become brighter than an entire galaxy. Shapley also made the claim that the Sun was located at the outer fringes of the Milky Way, which turned out to be more accurate than Curtis’ claims that the Sun was located in the center of the Milky Way. Plus, the true size of the Milky Way galaxy is now estimated to be larger than Curtis’ claims, but smaller than those of Shapley. ↩
Above the “VAR!”, an “N” is crossed out. It was previously thought that this star was in fact a nova, but upon discovering that it was in fact a variable, Hubble crossed out the previous label. ↩
The cepheid variable period luminosity relationship has been much better calibrated since that time, and other methods have been used as well. ↩
The research team speculate that the ring may be conforming to the shape of a standing wave – perhaps caused by the spin of the central galactic bulge and the lateral movement of gas across the galaxy’s large central bar. The researchers suggest that the combination of these forces may produce some kind of gravitational ‘sloshing’ effect, which would account for the unusual movement of the ring.
The ‘sloshing’ produces a very interesting and unusual shape.
“Strange objects, which persist in showing a type of spectrum entirely out of keeping with their luminosity, may ultimately teach us more than a host which radiate according to rule.”—Arthur Eddington, talking about Sirius B, a white dwarf star, in 1922. In astronomy, as is true in every other science, new discoveries arise when commonly held beliefs are challenged.
A self portrait of Spirit from 2007. Image Credit:NASA/JPL-Caltech
Attempts to start again communications with the Mars Exploration Rover Spirit are coming to a close. The last transmission ended on May 25, ending the series of communication efforts since March 22, 2010, when the rover last talked with Earth.
Spirit got stuck in soft soil in mid 2009, and numerous difficult maneuvers were attempted to free the rover. Ultimately, these movements were unsuccessful, and Spirit’s mission was transformed into conducting science from a stationary platform. Afterwards, efforts were made to turn the rover more favorably towards the Sun before the coming of the harsh Martian winter, so that Spirit’s solar panels would receive more light. However, these were not completely successful.
Spirit then faced a brutal winter on Mars, and due to low amounts of light falling on its solar panels, it likely did not have enough energy to power its internal heaters. Therefore, the critical components inside Spirit probably failed due to low temperatures.
The rover landed on Mars on January 4, 2004, and originally was designed for just 90 Martian days. However, Spirit lived long past that mission, extending its mission to more than 25 times longer than the original plan. Over that lifetime, Spirit relayed back numerous invaluable observations from Mars, such as rocks shapes suggesting alterations from water and the presence of carbonates.
On a personal level, the rover has been much more important than just its many accomplishments. I still vividly remember staying up till around midnight (yes, that was late for me then) to watch the live broadcast from JPL on NASA TV as it landed, waiting anxiously during the “six minutes of terror,” celebrating as it reached the ground, and waiting anxiously again while it bounced on the surface of Mars on its airbags. I desperately read and collected all the news items published in the newspapers from the discoveries that Spirit relayed back to Earth, and studied everything I could find out about its mission online. I examined every detail about the design of the rover and tried to imagine how it would function. As Spirit faced its many setbacks, I was continually impressed by the ingenuity of the scientists and engineers working on the project. They came up with some extremely creative solutions that just amazed me, like how to drive with just five of its six wheels when one failed.
Looking back, Spirit was not just a rover to me, but also an introduction to some of the most important things that I value and now enjoy. It inspired a love of robotics inside me, gave me all sorts of new ways to look at and understand the red planet, and, probably most importantly, instilled a great love of exploration. Spirit did a great part in showing me how important it is to keep pushing further to explore the unknown, and to press forward despite crippling setbacks.
Spirit will no longer be telling us more about Mars. But I think it’s important to instead keep in mind all the insights that Spirit has helped us discover, and, especially for me, the countless sources of inspiration it has provided.
The Galaxy Evolution Explorer (GALEX) and the Anglo-Australian Telescope on Siding Spring Mountain in Australia have conducted a five year survey of 200,000 galaxies. The survey, examining galaxies at up to seven billion years before the present time, has given an independent confirmation about the nature of dark energy.
The results provide further evidence to support the theory that dark energy works as a constant force. Essentially, the strongest current models of dark energy say that any volume of space has a constant and fundamental energy that gives that volume a negative pressure, causing it to expand. Dark energy is causing the expansion of the universe to speed up.
To be able to study the effects of dark energy, two different quantities have to be determined. The velocity and distance of objects need to be measured. The velocity can be found by looking at effects like the red shift of objects1. The distance can be measured with a few different reliable methods at this scale.
One method is to compare standard candles. Standard candles are objects whose luminosity is a set known amount. Type Ia supernovae have been used in the past as very reliable standard candles since they have extremely consistent behaviors, and more importantly for this purpose, extremely constant amounts of light, probably resulting from a very similar mechanism causing every nova. Knowing this can give the distance to an object when we compare its actual brightness with how bright we see it in the sky, since further away objects appear dimmer. This way, standard candles let us calculate distance to distant objects. Type Ia supernovae have been used in this way in the previous decade to determine the nature of dark energy.
This survey conducted by GALEX and and the Anglo-Australian Telescope, however, used standard rulers to measure distance. Like standard candles, standard rulers are objects that have a set known quantity, which in their case is a known length. By comparing the known length and the length that we can observe in the sky, the distance to an object can be calculated, since distant objects appear smaller. For the galaxy survey, the standard ruler was the distance between galaxies. Due to sound waves from the big bang, galaxies in pairs tend to be spaced apart from each other by about 500 million light-years. Using data on their separation distance, the distance to the galaxy pairs was able to be calculated.
Combining the distance data with velocity data gave details about dark energy. The evidence rules out early theories that gravity may be repulsive at larger scales, calling for a change in our understanding of gravity itself. Instead, what is being revealed is that there is a constant effect from dark energy, in support of current theories. What is particularly interesting about the project is that the standard candle method with Type Ia supernovae had been used before to suggest the same results. Now, confirmation is being found with a somewhat similar, but completely independent method, giving strong indications that current theories have a great amount of validity.
The redshift is caused by the Doppler effect. With sound, we notice it, for example, as the pitch of a moving car passing by changes. With light, as an object moves away, its waves are “stretched,” making it appear redder, and “contracted” if it moves closer, making it appear bluer. Furthermore, there is a redshift due to time dilation effects caused by special relativity as well. ↩
“As a society, we have been exploiting the powers of a universe to whose existence we are blind. Now we finally have the opportunity to end this alienation: the modern science of cosmology is discovering the universal reality in which we are all immersed.”—Joel R. Primack and Nancy Ellen Abrams, in The View from the Center of the Universe
I first picked up a copy of the Black Hole War1 last year, in the middle of my first semester at college. My first semester left countless impacts deep inside me, and on the ways I think about and perceive the world. Included among this was a new way that I had started to perceive physics and the process of science itself. I started to work with models and assumptions, and tackled problems in ways that I just hadn’t been exposed to previously in high school. I can attribute a lot of that to my physics classes, the Compass Project I had attended before the start of the semester, and also in a small and important way, this book.
The Black Hole War fits exactly in with that spirit of science itself, to which I finally got more fully exposed in my first few months at college. Unlike what is presented in the news and media today, the debate that this book describes in detail was a very real scientific question. A topic like global warming2, among other “issues”, is presented in news reports as being an ongoing debate when there is an overwhelming consensus among scientists, whereas this was something that scientists genuinely disagreed upon and were struggling to tackle. It describes how Leonard Susskind tried to understand what happens to information when it goes into a black hole, and how he had fought hard to show the validity of his viewpoint against other very capable physicists like Stephen Hawking.
Before even beginning the book, the topic seemed daunting at best. I was very interested in learning about black holes and their behaviors, but seeing the presence of subjects like quantum mechanics and string theory, I was also very cautious. Nevertheless, I hesitatingly started to delve into the book, waiting for the tough parts to come. Instead I was surprised to find that I was understanding nearly everything. Susskind was explaining the physics concepts so well, I was able to, with very little confusion, understand the nature of the problem and the process and thinking that went into forming his viewpoint. What still sticks out vividly in my mind was his clever analogies to explain the most odd situations that are associated with black holes. And yet, reading the book was not a passive experience, but a very immersive and thought provoking one. At every step along the way, I found myself wandering in my thoughts to better understand what was just shown, exploring the intricacies of the problems, or even trying to apply the same concepts to other phenomena that I had known about before. In the middle of the book, I still remember pausing to exclaim to myself that this is how physics topics should be presented. Near the end of the book, though, despite Susskind’s best efforts, I started to finally hit the roadblocks I had been expecting much before. I was stumbling over concepts like quantum chromodynamics, but by this point, I was far too excited about black holes to stop. This book did get somewhat difficult at times, but it challenged and provoked me like no other book really has, inciting me to keep reading and understand the difficult parts.
Above all, one of the reasons why I really valued reading this book was that it got me excited for my future as an astrophysicist and physicist. It gave me an inside account of how work in physics is done, and showed very well the entire intensely collaborative process. The account also demonstrated how the problems in physics are framed and then solved. I’m personally really looking forward to the type of work I may be able to do in the future, thanks in part to reading this book.