The Lake that Built a Mountain on Mars

NASA’s instrument-laden Curiosity Rover is now at the foot of Mt. Sharp, its ultimate target on Mars. New results from the rover have confirmed and filled in our ideas about what the 3-mile high mountain is doing in the middle of 96-mile wide Gale Crater. And, most important, the new observations give us even more confidence in the notion that ancient Mars was very different from Mars today – it may well have had a much thicker atmosphere, flowing rivers, and occasionally full lakes of water.

Mt. Sharp is an interesting mountain, in that it seems to be built up out of layer after layer of sediment. This material might have been carried to the center of the crater by either water or winds, scientists thought. The new results indicate that both water and wind may have had a role in building Mt. Sharp over the millennia.

We already knew that one or more dry river channels end at Gale Crater, making it likely that long ago, water probably flowed into the crater. Over long periods of time, the crater lake may have formed and evaporated again and again. Rivers flowing over the red sands of Mars would have carried quite a bit of sediment into the crater and would have deposited this material in its center. As the central mountain began to accumulate, the next river flood would lap up against it. The resulting waves could carry material higher than the river’s original level, thus building up the mountain further.

When the lake was dry, the big wind storms, that other instruments have shown us are a regular feature of Mars weather, could have added wind blown sand to the top of the mountain. So Mt. Sharp could have grown during both wet and dry periods.

Curiosity is only at the bottom of the mountain right now, but it has the ability to climb up to higher layers over the coming months. Scientists are very interested in what the layers higher up might reveal to us about how Mt. Sharp grew and how the climate on ancient Mars changed as time passed.

Our top picture, taken on Mars on Nov. 2, shows some of the layers building up at the bottom of Mt. Sharp in a formation scientists have nicknamed "Whale Rock." For a version of this picture that shows scale, see: http://photojournal.jpl.nasa.gov/figures/PIA19081_fig1.jpg 

The picture below is an earlier "selfie" that the Curiosity rover took showing its instruments and cameras at work. Click on either photo and you'll see a larger version, full of amazing detail -- straight from the surface of Mars!

A Rogue Black Hole Escaping its Galaxy

Astronomers have announced the possible discovery of a big black hole that has escaped the galaxy of stars that gave birth to it, a phenomenon that had been predicted in theory, but not observed.

Galaxies (great islands of stars) that share a neighborhood in space can sometimes collide. If each has a big black hole at the center -- as many galaxies do -- usually the two black holes collide and merge. But, under the right conditions, the black holes can engage in a "game of pool" (billiards for those with more refined tastes.)

One of the big black holes can "recoil" or "rebound," and wind up being shot out of the combined galaxies. This is a pretty unusual circumstance, and astronomers have been searching for an example. Now, it looks like they may have found one.

The project involved observations with several telescopes, including the Swift satellite and the giant Keck telescope in Hawaii. The galaxy that remains is called Markarian 177 (a name that comes from a catalog of disturbed galaxies made by an Armenian astronomer.) The object that may be the escaped black hole has a number from the Sloan Digital Sky Survey catalog -- SDSS1133.

The galaxy is about 90 million light years away in the bowl of the Big Dipper. As shown on the accompanying image, the rogue object is about 2600 light years from the center of the galaxy.

As black hole fans are now probably thinking as they read this, it's not the actual black hole we are seeing on this highly magnified Keck infra-red image. Black holes are black and hard to see against the black of space. The SDSS object is a black hole surrounded by gas and dust that the black hole is "eating." It is the ring of "food" that we see glowing on the picture.

There is a small possibility that the SDSS object is something else entirely, such as an exploding star, although there is evidence from earlier images against that interpretation. Astronomers plan to use the Hubble Space Telescope to get even more information about this mysterious pair of objects.

If the black hole interpretation holds up, this will be a new creature in the "astrophysical zoo" to add to the many weird things we have been discovering lately. Rogue black holes are already in use in science fiction (such as Allen Steele's novel "Spindrift") and may now join the real universe as well.

The Movie Interstellar: The Science Behind the Story

Lots of my students are asking questions about the new film Interstellar.  I have been hearing about the movie for some time; the studio even sent me a “teachers’ guide” that was not especially useful, but piqued my interest.  Most exciting for me was the news that the scientific advisor (and one of the producers of the film) was Prof. Kip Thorne of Caltech, who is arguably the world’s expert on black holes and wormholes -- and designed the science behind the “galactic subway system” in Carl Sagan’s novel and film Contact.

I wrote to Dr. Thorne and he told me that he had indeed been involved with Interstellar, and had, in fact written a book, entitled The Science of Interstellar, to explain the complicated science that was the basis for some of the more intriguing scenes and events in the film.   The book also tells the story of the film, which was always supposed to be strong on science, and, at one time, was set to be directed by Stephen Spielberg.  But that original deal fell apart and it took a while to bring Christopher Nolan, the film’s current director, into the project.

Dr. Thorne wasn’t the only scientist involved in the long period before the movie went from an idea to a completed production.  Yesterday, I was talking with Dr. Frank Drake, the father of the scientific search for extra-terrestrial intelligence, and he told me that he was on one of the early panels of scientists brought together (with Stephen Spielberg) to make sure the plot stayed close to real science and possible science.

With Christopher Nolan and his brother Jonathan (a writer of screenplays) involved, the film evolved from the script Dr.Thorne and producer Lynda Obst had first envisioned, to include much more about a future Earth facing ecological disaster.  Still, the original thought, to portray black holes and worm holes as accurately as modern science can make it, was high on everyone’s list of priorities.

A black hole is a place where the death and collapse of a huge star has produced such strong gravity, that space itself is “warped” -- and nothing, not even light can escape.  Near a black hole, time proceeds more slowly than in the rest of the universe, and this change in the flow of time becomes a major plot element in the movie.  Both the existence of black holes and their strange effect on time have been demonstrated by many experiments and are well established.

A wormhole is more speculative, but something Einstein himself thought a bit about.   It’s a place where a black hole or some other unusual feature of space and time becomes a tunnel (or short cut) from one place in space to another place very far away, or even to another time.  In a wormhole, the dangerous effects you would feel falling into a black hole are somehow kept at bay, so that a spaceship can go through it to elsewhere or elsewhen.

Both wormholes and black holes get major roles in Interstellar.  The astronauts in the movie first use a wormhole to get from our Milky Way Galaxy to another galaxy far far away.   Then, they wind up in the new galaxy in a location where there is a massive, spinning black hole, with planets around it.  I won’t give anything else away, except to say that the special effects showing the wormhole and the gargantuan black hole were composed from calculations made by Dr. Thorne and his team at Caltech, fed directly to the computers of the special effects team for the movie – and they are truly SPECTACULAR.

For more, I recommend reading Dr. Thorne’s book (pictured in this post) and going to see the movie – especially if you are a black hole fan.  Dr. Thorne also has a web page with some animations at: https://interstellar.withgoogle.com/transmissions

Landing on a Comet: High Adventure in Space

This Wednesday, a European landing craft called "Philae" will attempt humanity's first landing on a fast-moving comet (a complex chunk of ice approaching from the depths of space.)

After a 10-year, 4-billion mile journey to Comet Churyumov-Gerasimenko (C-G for short), the Rosetta spacecraft (which is now orbiting the comet) will drop a probe about the size of a kitchen range from a height of 13 miles.  Taking some 7 hours to slowly land on its icy target, Philae will be moving at only 2 miles per hour at the end.  Still, the gravity of the two-mile wide comet is so low, it could bounce off and move away or simply fall over and roll.   To prevent this, the designers have equipped Philae with harpoons to grab the comet and with legs that have rotating screws in them to hold on to the ice for dear life.

Our robot representatives have only landed on six worlds so far: the Moon, Mars, Venus, Saturn's moon Titan, and two asteroids.  None of those landings were quite as difficult and strange as this one.  It takes radio signals from Rosetta about half an hour to get back to Earth even at the speed of light.  Thus the European Space Agency controllers can't help Philae if it gets into trouble.  Its own computer software will have to make the decisions that will lead to its survival or loss. 

For a complete picture of Comet C-G, see my August 6 post.  The photo accompanying today's post is a fantasy montage, showing the Philae lander safely on the comet's icy, boulder-strewn surface.  The full comet has a weird L-shaped structure, as if two oval comets had somehow stuck together at a weird angle. Because its shape is so complex, its gravity is not simple either, making landing even more challenging. But if Philae lands, its 10 instruments will give us our first-ever up-close look at one of the chunks of ancient ice that are building blocks left over from the early days of our solar system. 

Keep your fingers and toes crossed that the landing succeeds.  For a basic animation of what the spacecraft will do and what instruments it carries, please see: http://www.youtube.com/watch?v=szKZ77MbF9Q  

A fuller documentary about the Rosetta mission, see: http://www.youtube.com/watch?v=cArihDTnOZg 

A Dark Spot on the Sun Seething with Energy

Many of you in North America who saw the partial eclipse of the Sun last Thursday may have noticed a nice dark spot under the eclipsed part of the Sun.  The full "active region" (that the visible spot is part of) is bigger in area than the giant planet Jupiter and has become the largest such feature on the Sun in 24 years.

With the kind permission of the photographers, I am posting here a beautiful close-up of the area, by Randall Shivak and Alan Friedman.  Look how wonderfully complex it is!

The darker regions on the Sun are called sunspots; they look darker because they are slightly cooler than the Sun's visible surface layer. The Sun is made entirely of seething hot gas, where the atoms are so hot, they easily lose their electrons.  This makes our Sun highly magnetic, and as it spins, its magnetic zones get all twisted up.  It's those twisted regions that appear to us as active regions.

Astronomers have already observed some "flares" -- sudden releases of extra energy -- from this region, but they haven't been sent in our direction in space.  The region is now facing the Earth as our Sun does its slow rotation.  So we may get some extra high -energy particles coming our way in days to come (or not -- weather from the Sun is as hard to predict as weather on Earth.)

For a nice movie of this region "crackling" with magnetic energy as the Sun rotates, see: http://apod.nasa.gov/apod/ap141022.html

A Comet Passes by Mars; An Eclipse of the Sun

 

On Thursday afternoon, Oct. 23, there will be a partial eclipse of the Sun, visible from the U.S. Different amounts of the Sun's area will be covered by the Sun. (For example, 40% of the Sun will be covered from the San Francisco region.) I have put question-and-answer introductions to the eclipse at: http://www.astrosociety.org/society-news/2014-eclipse-fact-sheets/

You can consult the national sheet for the degree the Sun will be eclipsed in your area. Here's wishing everyone clear skies. And please remember, do NOT look at the Sun without proper protection. Follow the instructions on the sheets or go to an astronomy place (observatory, college, planetarium) near you to join an eclipse viewing session.

This Sunday, Oct. 19th, a comet will pass closer to Mars, than any comet has passed to the Earth in recorded history. Comet Siding Spring (named after the observatory where it was discovered) will pass within only 87,000 miles of Mars. An armada of telescopes near Mars and Earth will try to get a good glimpse of it. From its orbit, this appears to be what you might call a "virgin" comet, making its first entry to the inner solar system. It is coming from the distant reservoir of ancient "icy chunks" that surround our solar system in a giant cloud.

A comet is just such an icy chunk that comes close enough to the Sun so that the Sun's energy and wind begin to evaporate the ice and loosen the dust frozen inside it for billions of years. These comets thus contain some of the original material from which our solar system was formed some 5 billion years ago. 

To learn more about NASA's plans for observing this Mars visitor, see: http://science.nasa.gov/science-news/science-at-nasa/2014/09oct_cometprep/

For a while, NASA scientists worried that dust from the comet may damage some of the spacecraft around Mars, but recent calculations are showing that the path the comet is taking means that its dust is not likely to pose a serious threat.  But we'll see Sunday.  Perhaps there will be faint "shooting stars" (dust burning up in the thin atmosphere) on Mars.

HBO is Showing "Einstein and Eddington" Now

In 2008, the BBC made a biopic (or dramatization) of events in Albert Einstein's and Arthur Eddington's life and work, and how they intersected. It was cosponsored by HBO and I just found out that HBO is currently showing this film (you can see it in the "On Demand" section of your cable TV offerings if you subscribe to HBO.) It may not last long, and it is not available on DVD yet in the U.S.

I recommend it with some enthusiasm (it's moving, and fun to watch), but also many reservations (the science and history are not always accurate, or -- to be charitable -- are twisted or changed in the interests of higher drama.)

I think everyone has heard of Einstein, but Arthur Eddington was an astronomer and physicist in England in the early part of the 20th century who contributed a lot to our understanding of how stars work. He was also a key member of the eclipse expedition in 1919 that tested if Einstein's crazy new theory of gravity, space, and time -- the general theory of relativity -- was correct. Measurements during that eclipse, and especially during a later eclipse made by a team from the Lick Observatory, established that Einstein was right and that the universe was more complex and beautiful in its inner workings than earlier scientists had imagined.

The film begins and ends around the eclipse expedition, but then goes back in time to set the scene. Many historical details are wrong or skipped over -- Elsa was divorced with two kids when she re-encountered Einstein in Berlin, the famous image of Einstein sticking out his tongue was later in his life, Eddington didn't have to tell Einstein about Mercury, etc. But such details don't matter to most viewers, and sometimes mixing things up a bit helps move the story along. And the flavor of the excitement around relativity is well characterized, with the two main actors doing a nice job in portraying the scientists and their personalities.

If you get HBO, or have a friend who does, and have a chance to see it, I recommend the film for everyone except historians of 20th century science, who will have a fit about those details. (The same production team also did a biopic about Stephen Hawking, called just "Hawking" and I gather you can find that film in segments on YouTube.)

Above you see the two scientists as portrayed in the movie, below you see the two of them from real life.
(For movie and TV fans, I can't resist adding: Gollum plays Einstein, Dr. Who plays Eddington.)