Venus occults or covers the star Lambda Aquarii April 17, 2014
A planet covering a naked eye star is rarer by far than a total eclipse of the moon, and yet Venus did just that yesterday afternoon (U.S. time) from Australia, New Zealand and Micronesia. No one in the northern hemisphere witnessed the event; Venus passed south of the star from our perspective.
Jonathan Bradshaw of Australia captured this exceptional alignment well in his video despite the shaky atmosphere. Lambda Aquarii, a 4th magnitude star in Aquarius, was wiped from the sky for all of seven minutes.
It’s believed that the last bright star Venus or any major planet covered up was 2nd magnitude Nunki in Sagittarius for observers in eastern Africa in November 1981. Venus next occults Pi Sagittarii in 2035 and bright Regulus on Oct. 1, 2044. Mercury will cover up Theta Ophiuchi on Dec. 4, 2015.
Mars will pass in front of Jupiter in an extremely rare planet-over-planet occultation on Dec. 2, 2223. Stellarium
Very rarely, planets pass in front of each other. Over the 300 year span from 1800 to 2100 only 7 “mutual occultations” of this sort have or will occur. Venus crossed in front of Jupiter in 1818 – that was the last observable one. The next will happen when Mars passes in front of Jupiter on Dec. 2, 2223. Clearly, you and I and even our kids won’t be around for that event, but maybe some of our kids’ kids will.
Nature shows that once again even the most unlikely things can happen as long as one key ingredient is available – oodles of time.
A view of Curiosity’s new digs called ‘the Kimberley’, named for a wilderness region in Western Australia. Taken on April 11 it shows tilted sandstones separated by windblown sands. The hilly rim of Gale Crater is seen in the distance. Click to enlarge. Credit: NASA/JPL-Caltech
NASA’s one-ton Curiosity rover has beamed back thousands of photos of amazing landscapes within Gale Crater since landing in August 2012. And that’s after driving only 3.8 miles, probably the distance to the nearest grocery store for many of us.
The Kimberley seen from orbit with the rover’s path highlighted. Curiosity rolled into the new location around the 589th Martian day or “sol”. Scientists selected the area based on pictures and studies made from orbit showing it to be rich in different rock types all exposed in the same location. Credit: NASA/JPL-Caltech
Earlier this month, the rover entered the Kimberley, a rise within the crater dotted with three buttes – Mounts Remarkable, Joseph and Christine – that exposes several varieties of rock scientists are eager to study. The area will be the focus of exploration for weeks to come before Curiosity resumes its journey to the slopes of Mount Sharp, a broad peak that rises 3 miles (5 km) from the crater’s floor.
Sandstones on Mars near the Kimberley photographed on March 29, 2014. Click to enlarge. Credit: NASA/JPL-Caltech
The Kimberley is strewn with some of the most beautiful sandstones yet seen on Mars. Sandstones form when water or wind carries along grains of sand until depositing them in a layer at the bottom of a stream or on the ground as in a desert. Minerals within the pore spaces between the sand grains cement the grains together to create sandstone. Sometimes layers of deposited sand can build up one atop another helping to further compact the material into stone.
Differing degrees of resistance to erosion result in a stair-stepped pattern visible in this photo taken 1/4 mile northwest of the Kimberley on Feb. 25, 2014. Steeper steps result from more resistant rock, so the flat, tan surface (foreground) is a weakly resistant sandstone. The small steps to the right center are a bit more resistant, and the steeper steps near the top of the scene are even more resistant. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS
Cement materials vary greatly. Clay minerals build sandstones that crumble with a rap of a hammer and more quickly erode in the Martian winds. Quartz cement creates a tougher rock more resistant to erosion. If you’ve ever marveled at the sight of a western, canyon-filled landscape, you’re seeing the varying resistance of sandstone to erosion at work. The same thing happens on Mars:
Another spectacular view of tipped and tilted sandstones with Mt. Remarkable in the distance photographed on April 11, 2014. Click to enlarge. Credit: NASA/JPL-Caltech
“A major issue for us now is to understand why some rocks resist erosion more than other rocks, especially when they are so close to each other and are both likely to be sandstones,” said Michael Malin of Malin Space Science Systems, San Diego. Malin added that variations in cement material of sandstones could provide clues to different types of wet environmental conditions in the area’s history.
Curious furrows are seen in the foreground in this photo taken at the Kimberley on April 3, 2014. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS
At Yellowknife Bay, Curiosity’s last major waypoint, erosion had exposed both sandstones and a lower layer of mudstone that was once part of an ancient lake bottom. The rover will be tooling around the Kimberley for a while – why not join the exploration by periodically checking out the Mars raw image archive?
A conglomerate rock formation at the Kimberley formed of boulders and rocks that were transported from elsewhere – by river or glacier for instance – and cemented together. Click to enlarge. Credit: NASA/JPL-Caltech/ MSSS
Brilliant Mars shines atop dimmer Spica in the constellation Virgo in this photo taken Sunday night April 6. The planet now rises at sunset and is easy to spot around 9:30 p.m. in the southeastern sky. Yes, we still have almost 4 feet of snow here in Duluth, Minn. Credit: Bob King
Mars reaches opposition today, its closest approach to Earth since Dec. 2007 and the brightest we’ve seen it since 2012. What a sight it’s become. Last night, while walking our respective dogs, my daughter took one look at the gleaming pink-orange “star” in the southeastern sky and knew immediately it was Mars.
About every two years, Mars and Earth line up on the same side of the sun at opposition. Because Mars’ orbit is eccentric (less circular than Earth’s) the two planets are closer at some oppositions than others. This year’s opposition is a relatively distant one. Illustration: Bob King
While it sounds like an act of defiance, opposition refers to Mars being on exactly opposite side of the sky as the sun. The planet rises at sunset this evening and sets when the sun pops up tomorrow morning. Not only is Mars out all night long, but being opposite the sun, it’s paired up closely with Earth on the same side of the sun as shown above.
One full rotation of Mars on April 8 created by Tom Ruen. North polar cap at top.
That’s why Mars is so doggone bright – it’s close! Of course we know that’s a relative term in astronomy. Today the Red Planet is 57.7 million miles away, which sounds rather terribly far. But keep in mind that it can be up to 249 million miles away. So yes, Earth and Mars are practically neighbors … for a little while. The same orbital motions that brought them together will also move them farther apart in the coming months.
Now here’s the kicker. Because the orbits of Earth and Mars aren’t perfect circles, the two planets are actually closest on April 14, six days past opposition. That’s the same night as the total eclipse of the moon. Even better, the moon will only be a “fist” away from the planet. What a sight they’ll make – two red orbs aglow in the southern sky.
Mars outshines its neighbors Spica and Arcturus in the east and is ever so slightly brighter than magnitude -1.46 Sirius off to the southwest. The map shows the sky around 9:30 p.m. local time tonight. Stellarium
The Red Planet far outshines the nearby stars Spica and Arcturus and at magnitude -1.5 glows a hair brighter than Sirius, the brightest star in the entire sky. While similar in brightness, their colors are dramatically different. Compare the two and tell us what you think.
One side of Mars, the side turned toward the Americas during the best observing times this week, shows relatively few features. Use the map below to help you identify other dark markings as they rotate into view in the coming days and weeks. North at bottom. Credit: Mark Justice
Mars won’t appear bigger or brighter until its next opposition in May 2016 so take a look at this miniature “eye of Sauron” beaming in the south the next clear night.
If you have a telescope, use a magnification of 150x or higher to look for the planet’s very tiny north polar cap (it’s summer there and the cap has shrunk!) and other dark markings on its surface. This week, the planet’s “blank” hemisphere is presented for observers in the Americas. Be patient. The more obvious features like Mare Erythraeum, Syrtis Major and Mare Acidalium will soon rotate into view (see map below).
Complete Mars map showing many more features. Click to learn more about Mars’ upcoming opposition. Credit: Association of Lunar and Planetary Observers (A.L.P.O).
Face southeast around 10:30 p.m. local time and you’ll be pleasantly surprised at the line of bright “stars” there. The brightest is the planet Mars. Photo taken March 24, 2014 at 10:30 p.m. Credit: Bob King
Last night Mars blazed in the treetops. I’m still amazed at how bright the planet’s become in the past few weeks. Paired up with the bright, blue-white star Spica in Virgo, it’s unmistakable. The two clear the southeastern horizon together around 9:30 and become very obvious an hour later.
The magnitude scale. Negative magnitudes are brighter than positive ones. Credit: Univ. Nebraska-Lincoln
Reach your arm toward Mars and move “two fists” to its upper left and you’ll spot Arcturus, the brightest star in the constellation Bootes the Herdsman. Together the three form a striking “lightsaber” of luminaries.
Looking more closely, you’ll notice that each is a different brightness. Thanks to fortunate circumstance, they differ from each other by almost exactly one magnitude, the standard unit of measurement astronomers use to measure star brightness.
First magnitude stars are 2.5 times brighter than second magnitude stars, which are 2.5 times brighter than stars of third magnitude and so on.
Mars rules the roost at magnitude -1.2, Arcturus is next at 0 and Spica at 1.0. If you’ve ever wondered what a magnitude of difference between celestial objects looks like, check this convenient live demonstration the next clear evening.
Arcturus and Spica will remain fixed in their brightness – at least for thousands of years – but the light of Mars and the other planets vary depending on their distance from Earth. In astronomy, there’s a simple rule: when close, objects appear brighter than when farther away. Mars’ magnitude varies more than most of the planets with extremes of -3.0 when nearest to 1.6 when most distant. That’s a difference of nearly 100 times.
Because Mars’ orbit is more elliptical than Earth’s, distances between the two planets are vary significantly, causing the planet to vary greatly in brightness. Credit: Wikipedia with additions Bob King
These large variations directly relate to Mars’ more elliptical (oval) orbit. When the Red Planet is on the far end of its elliptical orbit at the same time Earth’s on the opposite side of the sun, it’s farthest and faintest. When on the far end of its orbit on the same side of the sun as our planet, it handily outshines every star and planet in the sky except Venus.
Mars on March 19, 2014 with some of its more prominent features marked. Hellas and Syrtis Major are relatively easy to see. The north polar cap is quite small now. Credit: Damian Peach
Even if you don’t give two shakes about magnitudes, make sure you take in a view of all three of these night sky gems. If you have a telescope and are observing from the western hemisphere, this is the best week to see the bright false south polar cap.
The “cap” is really Hellas, the largest crater on Mars, covered in frost and bedecked with clouds during southern hemisphere winter.
Look for a bright lens-shaped spot on the planet’s south end around midnight early this week and closer to 1-2 a.m. next weekend. It’ quite obvious in 6-inch and larger telescopes in steady air.
Mars (upper left), Spica in Virgo and the waning gibbous moon will put a smile on your face when they come in the southeast tonight March 18 around 10:30-11 p.m. Stellarium
Tonight after 10:30, look over to the southeast and you’ll see a remarkable triangle of celestial lights: Mars, Spica and the waning gibbous moon. For those who remember their geometry the threesome will form either an equilateral, isosceles or right triangle depending on the where you live and time of night.
Mars on March 14, 2014 photographed from Athens, Greece. The north polar cap is at bottom. What appears as a polar cap in the south (top) are clouds and frost in a large crater on the planet called Hellas. At left is a patch of evening clouds. Credit: Manos Kardasis
Fiery Mars now outshines Spica and all the nighttime stars except Sirius, the brightest star in the sky. It’s rapidly approaching its April 8 opposition when our two planets will be their closest since early 2008. A closer Mars means a bigger view in the telescope – the planet’s disk has swollen to more than 13 arc seconds wide, large enough that observers with 6-inch and larger telescopes using magnifications of 150x and higher can spy a variety of dark markings on its dusty surface.
Curiosity snapped this photo of the barren, rocky landscape of Mars on March 16. Click to enlarge. Credit: NASA/JPL-Caltech
One of the most prominent Martian features this season is the north polar cap, but you’d better look quick. With summer underway in Mars’ northern hemisphere, the cap has been steadily shrinking, and now appears as small dab of white along the planet’s northern edge or limb.
Martian winds pick up dust and swirl it around to create dust devils just like the ones on Earth. These are tracks left by dust devils in the planet’s Utopia Planitia region on Jan. 19, 2014. Click to enlarge. Credit:NASA/JPL/ASU
For more on interesting things to see on the Red Planet in the coming weeks, please check out a recent article I wrote for Universe Today. You’ll also want to download Meridian, a free and useful program to help you know what features on Mars are facing you at any time of night or day.
1918 post card that citizens could mail to their congressman to show support for the daylight saving time law, which was enacted on March 19, 1918 in the U.S. Click to read the history of DST. Credit: Library of Congress
It happens every year. The seasonal westward drift of the stars is temporarily put on hold when we “spring forward” an hour on the second Sunday in March.
With daylight saving time or DST we gain an hour of evening daylight and lose an hour of early morning light. After a long winter, who doesn’t welcome more light at the dinner hour?
A one-hour later sunset naturally means an additional hour for night to begin. Yesterday, twilight ended and true night began around 7:45 p.m. Darkness descends tonight around 8:45 p.m. Since we’ll have to wait that extra hour for stars to come up in the east, the time change has the effect of retarding every star’s rising by an hour.
Sirius, the brightest star, heads up the constellation Canis Major the Big Dog and is very prominent in the southern sky this month. With the start of daylight saving time, it now appears one hour east (to the left) of where it was last night at the same clock time. Stellarium
For instance, last night around 8:30 p.m. I watched brilliant Sirius twinkle west of due south. When the clock glows 8:30 p.m. tonight, Sirius will sparkle east of due south. The same holds true for Orion and the other winter stars. Compared to last night at the same clock time, the winter constellations will be higher up in the sky. Meanwhile, the spring constellations of Leo, Virgo and Bootes, which have been steadily gaining ground in the east, will be shoved back an hour.
While it’s not a great hardship, it does mean that to see the cool spring stuff, we have to go out an hour later compared to a night ago. I’ve been watching Mars finally make its way into the evening sky. To observe it now means getting out at midnight instead of 11. Oh well.
All will take care of itself in due time. We’ll come to accept the change, just as our bodies will finally figure out to do with the hour we lost. And since the westward drift of stars with the seasons never stops, come late-April, Sirius and friends will be memories and bright Arcturus and Mars will gleam in the southern sky.
View of Earth’s orbit around the sun seen from above the north pole. As we zip along at 18.5 miles per second, we see a different set of constellation in the night sky depending upon where we are in our orbit. From this moving perspective, the background constellations appear to drift to the right or westward. Credit: Bob King
As Earth travels in its orbit around the sun at 18.5 miles per second, we peer into a different direction in space as the weeks and months pass. Think of going for a ride on one of those merry-go-round horses at a carnival. As the merry-go-round turns, we look out to see a different part of the fairground as the seconds pass. After one spin, the view repeats until the ride is over.
If you substitute the Earth for the horse and our orbit for the merry-go-round, the very same thing happens during a year’s stargazing with the view repeating once every year. During Earth’s “little spin” around the sun, we see the stars and constellations drift from east to west across the sky as we pass them by.
This isn’t the same as the nightly rising and setting of stars – that’s due to Earth’s rotation. Every star you see makes a complete circle around the sky in 24 hours. The much more leisurely seasonal drift is superimposed on that pattern and reveals itself to sky watchers who spend time regularly under the stars.
Cosmos trailer on Fox-TV. The series will air at 8 p.m. Central Time Sundays starting tonight
A final note. The new 13-part “Cosmos” TV series, hosted by astrophysicist and astronomy popularizer extraordinaire Neil deGrasse Tyson, starts tonight on Fox-TV at 8 p.m. CDT (Central time) and 9 p.m. Monday nights on the National Geographic Channel. Don’t miss it!
This scanning electron microscope image shows spheroidal features embedded in a layer of iddingsite, a mineral formed by action of water, in the Yamato 000593 meteorite. An area with the spheres, circled in red, was found to have about twice as much carbon present as an area (circled in blue) without the spheres. The measure at left is one micron (.001 mm) or about the size of some bacteria. Credit: NASA
A team of scientists at NASA’s Johnson Space Center in Houston and the Jet Propulsion Laboratory in Pasadena, Calif., has found evidence of past water movement and tiny carbon-rich spherules in Martian meteorite Yamato 000593.
The 30-pound (13.7 kg) chunk of Mars was collected on the Yamato Glacier in Antarctica by the Japanese Antarctic Research Expedition in 2000. It was once part of a 1.3 billion year old Martian lava flow but was ejected by a meteorite impact 12 million years ago and landed near the south pole some 50,000 years ago.
Scientists distinguish Mars rocks from Earth’s by the atmospheric gases trapped inside (these are compared to measurements of the planet’s atmosphere made in situ by our Mars landers) and the distinctive composition of oxygen in the minerals making up the rock. Martian rocks contain a greater proportion of oxygen’s heavier forms, called isotopes, compared to Earth rocks.
This scanning electron microscope image of a polished thin section of a meteorite from Mars shows tunnels and curved micro-tunnels deep within Yamato 000593. Iddingsite is a clay mineral indicating that water once flowed through cracks in the rock. The scale bar at lower left is 2 microns. Credit: NASA
The team made two fascinating discoveries when they peered closely into the interior of the meteorite:
* Micro-tunnel structures with curved, undulating shapes that thread their way through the rock and resemble similar textures reported by other researchers in terrestrial basaltic glasses created by bacteria.
* Distinct nanometer- to-micrometer-sized spherules resembling bacteria that are sandwiched between layers within the rock and enriched in carbon compared to their surroundings.
Similar bacteria-like structures are found inside the Martian Nakhla meteorite that fell in Egypt in 1911. Credit: NASA / ARES / JSC
Similar spherical features were previously seen in the Martian meteorite Nakhla that fell in Egypt in 1911. Everett Gibson, who led the new study, was also involved in the 1996 study of Allan Hills 84001, the first Martian meteorite thought to be touched by life’s imprint. I’ll never forget the excitement and controversy at the time when it was announced that possible evidence of life in the form of worm-like structures and organic molecules were found within the meteorite.
Bacteria-like structures in the Martian Allan Hills 84001 (ALH 84001) meteorite discovered in Antarctica in 1984. Credit: NASA
We know now that virtually all potential “signs of life” found by the 1996 researchers could have been created by chemical and other inorganic processes, making the team’s results inconclusive at best.
Likewise, Gibson and Lauren White, lead author of the recent paper on Yamato 000593 in the International Journal of Astrobiology, allow that non-living processes could have cooked up the carbon-rich structures and micro-tunnels. Still, the similarities between structures in basaltic Earth rocks and Yamato 000593 might also imply life’s handiwork on a planet other than our own.
Rock-eating bacteria – called endoliths – inside a basaltic rock found 3,900 feet (1,200 meters) beneath the Indian Ocean floor. Credit: NOAA Ocean Explorer
“As more Martian meteorites are discovered, continued research focusing on these samples collectively will offer deeper insight into attributes which are indigenous to ancient Mars,” said White. “As these meteorite studies are compared to present day robotic observations on Mars, the mysteries of the planet’s seemingly wetter past will be revealed.”
Knowing how scientists relish testing any new claim, especially one hypothesizing early life on Mars, the story of Yamato 000593 can’t help but be revised and expanded in the months and years ahead.
After crossing a sand dune from Dingo Gap into the less rugged Moonlight Valley, Curiosity looked back to photograph the scene. For scale the distance between the tracks is 9 feet (2.7 meters) and the dune is about 3 feet (1m) tall. Click to large version. Credit: NASA/JPL-Caltech
Have you ever taken a different way home just to avoid pothole-riddled roads? If so, you’re thinking just like the team driving the Mars Curiosity rover. Alarmed that the tough, air craft grade aluminum wheels were getting overly dinged up and punctured by sharp rocks, NASA commanded the rover to leave the higher ground, cross Dingo Gap (Feb. 6) and head for sandier, less rocky terrain.
This map shows the route driven and route planned for Curiosity from before reaching “Dingo Gap” (upper right) to the mission’s next science waypoint, “Kimberley” at lower left. The poiint marked 547 is where the rover finished its long drive on Feb. 18. Click to enlarge. Credit: NASA/JPL-Caltech/Univ. of Arizona
On Tuesday, Feb. 18, the rover covered 329 feet (100.3 meters), the mission’s first long trek that used reverse driving and its farthest one-day advance in more than three months.
Closeup of one of Curiosity’s wheels taken by the Mars Hand Lens Imager camera on Feb. 21, 2014 showing numerous dings. Click to learn more about how the wheels work. Credit: NASA/JPL-Caltech
Driving backwards lessens wheel damage from sharp rocks and has been used – to different purposes – on both the Spirit Rover and Opportunity. Spirit was helped when one of its front wheels stopped working; Opportunity drives backwards half the time to distribute lubricant evenly in all wheels. I don’t recommend the backwards technique when dodging potholes in the earthly realm.
Curiosity’s got about 2/3 miles (1.1 km) of mostly valley travel until it reaches its next scientific waypoint “Kimberley”, named for the northwestern Australia region with very old rocks. A variety of different rock types meet at the location making it a great spot to use the sample-collection drill to gather and analyze powdered samples of new material.
Curiosity took this photograph on Feb. 21, 2014 somewhere between Violet Valley and Kylie. The sandy terrain still has its share of sharp rocks. Curiosity’s wheels were expected to take a battering, but NASA decided to be cautious to increase their life. Click to enlarge. Credit: NASA/JPL-Caltech
Curiosity has driven 937 feet (285.5 meters) since the Feb. 9 dune-crossing and a total of 3.24 miles (5.21 km) since its August 2012 landing.
Erosion-exposed mineral veins in Dingo Gap. Credit: NASA/JPL-Caltech
Look to the southeast this evening after moonrise to catch this star-planet-lunar trio. This map shows the sky around 11:30 p.m. local time. Stellarium
We just received another 11 inches of snow on top of the four feet that’s been lounging about the yard the past couple months. I’ve rarely seen such an abundance of whiteness. Then this morning, a chill fog condensed on every protrusion it could find, covering all in hoarfrost. When the night rolls around the stars add crystal shimmers of their own. Is this the best season or what?
Thick frost coats branches on a tree in Duluth, Minn. after an early morning fog today. Credit: Bob King
I know many reading this are ready for winter to be finished. If too much snow and cold give you the blues, may I direct your attention to a pleasing arrangement of the waning gibbous moon, the blue-white star Spica and ruddy Mars in the late evening sky tonight?
The late-rising trio comes up around 11 p.m. local time but will show best by midnight or later. If you get up early for work or school, look off to the southwest during early morning twilight to catch the scene.
At that hour, the moon’s eastward orbital motion will have changed the shape of the triangle entirely.
I just received an review copy of the Carl Sagan classic bestseller Cosmos re-published in paperback with a a new forward by astrophysicist and astronomy popularizer / comedian Neil deGrasse Tyson. If you’ve never read Cosmos, take this opportunity to pick up a copy.
DeGrasse Tyson will be hosting a brand new remake of Sagan’s Cosmos TV series series starting March 9 on Fox at 8 p.m. Central Time Sundays and 9 p.m. Mondays on the National Geographic Channel.
The once-mystery rock – called Pinnacle Island – is shown near its mate Stuart Island alongside Opportunity rover tracks in this photo taken on Feb. 4, 2014. It showed up in front of the rover in an image taken on Jan. 8, 2014 at a location where the rock had been absent in an image taken four sols (Martian days) earlier. Click to enlarge. Credit: NASA/JPL-Caltech
We all love a good mystery, but to be honest, many of us enjoy it even more when a mystery’s finally solved. The “jelly doughnut” Mars rock that mysteriously appeared in front of the Opportunity Rover on January 8 turns out to be a piece of a larger rock broken and moved by the rover’s wheels earlier that month.
The original rock, dubbed Stuart Island rests about 3 feet (1-meter) away and has a similar dark-red center and white edge as Pinnacle Rock.
“Once we moved Opportunity a short distance, after inspecting Pinnacle Island, we could see directly uphill an overturned rock that has the same unusual appearance,” said Opportunity Deputy Principal Investigator Ray Arvidson. “We drove over it. We can see the track. That’s where Pinnacle Island came from.”
A stereo version the first scene helps us to see the contours of the landscape. To see in 3-D, don a pair of those blue-red glasses. Click to enlarge. Credit: NASA/JPL-Caltech
Researchers used the microscopic imager and alpha particle X-ray spectrometer on Opportunity’s robotic arm to examine Pinnacle Island for several days in January. The rock is unusual in that it contains high levels of elements such as manganese and sulfur, suggesting these water-soluble ingredients were concentrated in the rock by the action of water.
There you have it. Now it’s time to move on to the next mystery: Why do people sue NASA for delusional claims of alien life on Mars?