Comet Finlay outburst another present under the Christmas tree

Morphing from obscurity to prominence, Comet 15P/Finlay shows off a beautiful finger-shaped tail, a bright nucleus and several rays in this photo taken December 19th. It orbits the Sun every 6.5 years. Credit: Damian Peach

Surprise! An obscure comet that only amateur astronomers would pay attention to experienced a sudden outburst in brightness earlier this week putting it within range of telescopes as small as 4.5 inches.

Comet 15P/ Finlay hunkered along at a dim 11th magnitude successfully avoiding the limelight until about December 16th. That’s when Czech comet observer Jakub Cerny and his team took a photo revealing the comet had surged in brightness by some 8 times to magnitude 8.7. Suddenly, Finlay became a minor celebrity.

Comet Finlay on December 16th shows a bright coma and short tail. Its sudden rise to 9th magnitude was confirmed on December 18th by Australian comet observers. The moderately condensed object is about 3 arc minutes in diameter. Credit: J. Cerny, M. Masek, K. Honkova, J. Jurysek, J. Ebr, P. Kubanek, M. Prouza, M. Jelinek

It still remains in outburst visible low in the southwestern sky very close to the planet Mars, which serves as a convenient “pointer” to help us find it. From mid-northern latitudes, Comet Finlay is best viewed as soon as evening twilight ends, when highest in the sky. The moon, ever a spoiler when it comes to viewing fuzzy stuff like comets and galaxies, won’t be over-bright until after Christmas, leaving us almost a nearly week-long window for finding and tracking the comet before it fades.

Use the general map to take you to Mars and then the more detailed version to pinpoint the comet’s location. Finlay will look like a small, fuzzy spot with perhaps a faint tail to the east visible depending on the size of your telescope.

To find the comet, first find Mars. Face west toward the brilliant star Vega and shoot a line from it through Altair and straight to Mars, low in the southwestern sky in Capricornus. Map time is around 6:15 p.m. CST, end of evening twilight in late December. Source: Stellarium

Planet and comet paths are currently converging toward conjunction. On December 23rd and 24th Mars and Finlay will be separated by just 10 arc minutes or 1/3 the diameter of the Full Moon. By December’s end they’ll gradually separate as each follows its own orbital path around the Sun. The close pairing is line of sight only.

Comet Finlay tracks alongside Mars through early January. On December 23rd, they’ll come together in a remarkably close conjunction. This map shows the nightly position of the comet from Dec. 18th through Jan. 12th. Mars’ location is shown every 5 nights. Positions plotted for 6:15 p.m. (CST). Stars shown to magnitude 8. Star magnitudes are underlined. Click for a large version you can print for outside use. Source: Chris Marriott’s SkyMap software

We’ve known about Comet Finlay since September 26, 1886, when William Henry Finlay happened across it with his 7-inch telescope from the Cape of Good Hope in South Africa. He described humanity’s first view of the object as round, 1 arc minute in diameter and “very slightly more condensed towards the centre.”

Animated movie showing the expansion of the coma of Comet 17P/Holmes over 9 nights during its spectacular outburst in November 2007. Credit: 3.6-meter Canada-France-Hawaii telescope on Mauna Kea / David Jewitt

Finlay reaches perihelion or closest approach to the Sun on December 27th and was expected to brighten to magnitude +10 when nearest Earth in mid-January at 130 million miles (209 million km). This month’s outburst may change that prediction.

What causes a comet to quickly and unpredictably surge in brightness still baffles astronomers. Unlike most rocky asteroids, comets are friable creatures. They crumble easily. It’s thought that sub-surface ices, warmed by a comet’s approach to the Sun, vaporize, creating pressurized pockets of gas that break through the overlying ice above, sending fragments flying and exposing fresh new ice.

Sunlight gets to work vaporizing both the newly exposed vents and aerial shrapnel. Large quantities of dust trapped in the ice are released and glow brightly in the Sun’s light, causing the comet to suddenly brighten.

Comet Lovejoy Q2 looks like a spectacular aerial burst in this photo taken December 20, 2014. The comet’s still low in the southern sky from mid-northern latitudes but will be soon be well-placed for binocular viewing in a few days. Credit: Martin Mobberley

So now we have two fairly bright comets during the holidays – Finlay and Comet C/2014 Q2 Lovejoy. Lovejoy has been steadily brightening and now glows at around magnitude 5.5, bright enough for observers with dark skies to see it with the naked eye. Click HERE for more information and a finder chart for it.

While this means we have two cometary gifts under the Christmas tree, by all means, don’t wait until Christmas to unwrap either. Have at them the next clear night!

Who or what passed gas on Mars?

A photo taken today, December 19th, of sand dunes and rock outcrops around the Curiosity rover through the fisheye lens of one of its Hazard Avoidance Cameras. Colorized by the author. Credit: NASA/JPL-Caltech

What a tantalizing week it’s been for organic chemistry on Mars. We learned that NASA’s Curiosity rover measured a tenfold spike in methane, an organic chemical, in the atmosphere around it and detected other organic molecules in a rock-powder sample collected by its drill.

Scatalogical references to the contrary, methane is a colorless and odorless gas. While it’s a component of both human and bovine flatulence, what gives human “gas” its odor are sulfur compounds, principally hydrogen sulfide and methyl mercaptan, which by the way we share with skunks.

But I digress.

This image illustrates possible ways methane might be added to Mars’ atmosphere and removed from it and stored in “sinks”. The Curiosity rover has detected changes in methane concentration in the atmosphere, implying both types of activity occur on modern Mars. More details of methane’s formation and movement on the planet are given below. Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan

“This temporary increase in methane — sharply up and then back down — tells us there must be some relatively localized source,” said Sushil Atreya of the University of Michigan, Ann Arbor, and Curiosity rover science team. “There are many possible sources, biological or non-biological, such as interaction of water and rock.”

Methane molecule

The sudden increase and decrease immediately gets the heart palpitating. Sure sounds like the work of a living being, but methane, a simple organic molecule made of one carbon atom festooned by four hydrogen atoms, can be created in a number of different ways. Bacteria make methane by combining carbon dioxide and hydrogen; the energy liberated in the process powers their minute lives.

Chemical reactions between water and the minerals olivine and pyroxene in rock also release methane as does the action of ultraviolet light from the Sun on organic materials like comet dust and other meteoric material on Mars. Whether manufactured through living or non-living processes, methane generated underground can become trapped within the crystal structure of water to form a curious substance called clathrate, a form of methane ice.

This 98-foot-wide (30-meter) crater spotted in Siberia this past summer was probably caused by the release of methane gas from permafrost. Click to learn more about it. Credit: Yamalo-Nenets Autonomous Okrug Governor

Meteor impacts, faults or cracks in the Martian crust and simple outgassing can then release methane at a later date. Earth has abundant methane clathrates buried beneath deep ocean sediments and stored in permafrost. We hope it stays there. Methane is a powerful greenhouse gas that already plays a role in climate change. Unlike chocolate, more of it isn’t a good thing.

Since Mars is a windy planet, any methane released is likely to quickly thin out and be dispersed. Methane can be removed from the atmosphere through “photochemistry” or the sunlight’s UV light sparking chemical reactions among molecules. These reactions can oxidize the methane, through intermediary chemicals such as formaldehyde and methanol, into carbon dioxide, the predominant ingredient in Mars’ atmosphere.

This graphic shows tenfold spike in the amount of methane in the Martian atmosphere surrounding the Curiosity rover as detected by a series of measurements made with the Tunable Laser Spectrometer instrument in the rover’s Sample Analysis at Mars laboratory suite. Credit: NASA/JPL-Caltech

Researchers used Curiosity’s onboard Sample Analysis at Mars (SAM) laboratory a dozen times in a 20-month period to sniff methane in the atmosphere. During two of those months, in late 2013 and early 2014, four measurements averaged seven parts per billion. Before and after that, readings averaged only one-tenth that level.

Whatever its origin, we’re not talking much gas – Earth’s atmosphere, of which methane is a minor constituent, averages 1,800 parts per billion. Cattle belching alone accounts for 16% of that total.

Curiosity also detected different Martian organic chemicals in powder drilled from a rock dubbed Cumberland, the first definitive detection of organics in surface materials of Mars. These Martian organics could either have formed on Mars or been delivered to Mars by meteorites.

There’s abundant evidence for Mars once being a wetter world. These riverbeds, called Nanedi Valles, flowed with water about 3.8 billion years ago. Credit: ESA

As we saw with methane, organic or carbon-containing materials aren’t necessarily an indicator of little green bugs. They can form and be left in rocks through inorganic processes, too. There’s simply no way to know from the Curiosity data how they originated, but they do give us hope that Mars was once (and may still be) a planet favorable to life.

Identifying which specific Martian organics are in the rock is complicated by the presence of perchlorate minerals in Martian rocks and soils. Perchlorates are toxic salts used for propellents here on Earth because they have explosive properties. When heated inside SAM, the perchlorates alter the structures of the organic compounds, masking the identities of the organics in the sample.

Curiosity also revealed some interesting news about the past water in the Martian atmosphere. According to its measurements, the Cumberland rock formed 3.9 to 4.6 billion years ago and contains just half the ratio in water vapor in today’s Martian atmosphere. This suggests that much of the planet’s water loss occurred since that rock formed.

View of a rocky desert-like landscape inside Gale Crater snapped by Curiosity on December 14th. Colorized by the author. Credit: NASA/JPL-Caltech

On the other hand, the ratio is about three times higher than that estimated in the original water supply of Mars. This suggests much of Mars’ original water was lost before the rock formed. More information please!

Additional samples along with data from the NASA’s MAVEN mission, which is conducting a study of the planet’s atmosphere to determine where both the water and air disappeared to, will hopefully give us a clearer picture of the Red Planet’s evolution from a water world like Earth to the present cold, dry desert.

In more recent news, NASA and an international team of planetary scientists have found evidence in meteorites on Earth that indicates Mars had yet another global reservoir of water or ice near its surface. Check out the details HERE.

Source information in today’s blog

Curiosity Rover discovers Gale Crater was once a massive lake

Simulated view of Gale Crater Lake on Mars receiving runoff from snow melting on the crater’s northern rim. Evidence that NASA’s Curiosity rover has found of ancient streams, deltas and lakes suggests the crater held a lake such as this more than three billion years ago.  Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

Evidence gathered by NASA’s Curiosity Rover during its 2-year-plus study of soil and rocks in Gale Crater points to a startling conclusion: this 96-mile-wide crater once held a lake some 900 feet deep.

Gale Crater now with Mt. Sharp at center. Credit: NASA/JPL-Caltech

Mount Sharp, the crater’s broad central peak, stands about 3 miles (5 km) tall and was built by sediments deposited in the lake over tens of millions of years by wind, rivers and material settling to the lake bottom. Curiosity is currently investigating the lower 500 feet (150-meters) of sedimentary rock at the base of the mountain where hundreds of layers of rock are exposed like so many layers of a Vienna torte.

This picture shows a vertical cross section through geological layers deposited by rivers, deltas and lakes. Deposits from a series of successive deltas build out increasingly high in elevation as they fan out toward the center of the crater over the lake deposits. 10 centimeters equals about 4 inches. Credit: NASA/JPL-Caltech/Imperial College

All this activity occurred an estimated 3 billion years ago when the atmosphere of Mars had to be much denser than it is today. For water to exist out in the open on a planet, sufficient atmospheric pressure is needed to prevent it from vaporizing into thin air. Literally. Mars’ atmospheric pressure today is 1/1000 that of Earth, much too tenuous to keep water down.

“We are making headway in solving the mystery of Mount Sharp,” said Curiosity Project Scientist John Grotzinger of the California Institute of Technology in Pasadena. “Where there’s now a mountain, there may have once been a series of lakes.”

This view from the Mastcam on NASA’s Curiosity Mars rover shows an example of cross-bedding that results from water passing over a loose bed of sediment in one direction and then another. It was taken Nov. 2, 2014, at a target called “Whale Rock” within the “Pahrump Hills” outcrop at the base of Mount Sharp. Credit: NASA/JPL-Caltech/MSSS

Only problem is, scientists still can juggle the models to arrive at a satisfactory explanation for why the Martian climate was so radically different in the distant past. Hypotheses abound. Was it the decay of the planet’s magnetic field and stripping of its atmosphere by the solar wind or did intense asteroid bombardment send it flying into the vacuum of space?

Whatever happened, over time, the water evaporated, vaporized or seeped away, and sediments hardened into rock. Winds howling for hundreds of millions of years carved away at the material between the crater’s rim and what is now the edge of the expansive Mt. Sharp, exposing layer upon layer of the crater’s past.

This series of images reconstructs the geology of the region around Mars’ Mount Sharp, where NASA’s Curiosity Mars rover is now exploring. The images, taken on Earth, have been altered for the illustration of how sediments can accumulate in alternating dry periods and wet periods. A dry period is shown at left, wet at center and dry again at right. Over time, sediments accumulate and are piled higher on the crater floor through the action of water. Credit: NASA/JPL-Caltech

“We found sedimentary rocks suggestive of small, ancient deltas stacked on top of one another,” said Curiosity science team member Sanjeev Gupta of Imperial College in London. “Curiosity crossed a boundary from an environment dominated by rivers to an environment dominated by lakes.”

Scientists are left with a conundrum — how did Mars produce the conditions that would keep liquid water stable for millions of years, long enough for lakes and rivers to deposit hundreds of feet of sediments? For now, it’s just enough to know it happened, and that what appears to be a dusty, rocky depression once held more water than Lake Erie.


The Moon, still young after all these years / See a Callisto eclipse!

The Moon and Mars gather in the west at dusk this evening. Stellarium

Tonight the returning young crescent Moon puts down stakes near the planet Mars in Sagittarius. Look for the pair low in the southwestern sky at dusk.

We’re used to hearing how ancient the Moon is. Its origin goes back to 4.48 billion years ago when a Mars-sized planet sideswiped the Earth, blasting debris into space that quickly coalesced into our satellite. While it’s true that most of the Moon’s crust and craters date from then, recent close-up photos from NASA’s Lunar Reconnaissance Orbiter (LRO) suggest the Moon remained volcanically active until not that very long ago. At least on geological time scales.

Ina Caldera, a classic IMP, sits atop a low, broad volcanic dome or shield volcano, where lava once oozed from the moon’s crust. The darker patches in the photo are blobs of older lunar crust. They  form a series of low mounds higher than the younger, jumbled terrain around them. Credit: NASA

100 million years ago, when dinosaurs cracked jokes about the early mammals, lava oozed from cracks in the Moon’s crust to create what astronomers nowadays call IMPs or Irregular Mare Patches. They’re characterized by a mixture of smooth, shallow mounds next to patches of rough, blocky terrain. Only one, called Ina, is large enough to see in amateur telescopes. The others, liberally sprinkled across the lunar nearside, are generally less than 1/3 mile (500 m) across. Using the LRO, a team of researchers led by Sarah Braden of Arizona State University has found 70 landscapes similar to Ina.

When it comes to the big picture, 100 million years is a small slice of Earth’s history. Credit: NASA

Maria (plural of “mare”) are those big dark spots the make up the face of the man in the moon. They’re actually huge expanses of lava that welled up from cracks in the Moon’s crust several billion years ago after asteroid impacts. IMPs are much more recent. Some may be as “young” as 50 million years old. This was well after the dinosaurs succumbed to major climate changes induced by the impact of a 6-mile-wide asteroid hit here on Earth. Now the mammals are cracking jokes about the dinos.

A selection of some of the 70 IMPs discovered during the survey. Credit: NASA

“Discovering new features on the lunar surface was thrilling!” says Braden. “We looked at hundreds of high-resolution images, and when I found a new IMP it was always the highlight of my day.”

Astronomers determine ages of lunar features by doing crater counts. The more lightly cratered an area is, the younger.

Here’s the scene tomorrow morning November 26th with all four of Jupiter’s bright moons. Callisto, which sits right next to Europa, will dramatically fade over several minutes time starting about 4:50 a.m. CST. Meanwhile, 15 minutes later at 5:05 a.m., Ganymede will exit its eclipse and return to view. Add one hour for EST, subtract an hour for MST and two hours for PDT. South is up. Stellarium

Some of you may be early morning observers. Well, I’ve got a special event to share with you. Tomorrow morning November 26th, Jupiter’s bright moon Callisto will be eclipsed by Jupiter’s shadow starting at 4:50 a.m. (CST) and disappear for nearly five hours.

Just 15 minutes after Callisto disappears, Ganymede emerges from eclipse at 5:05 a.m. (CST). One disappears, the other reappears. Pretty cool! Jupiter will be the brightest thing in the sky high in the south in Leo at the time. You can always find out what Jupiter’s moons anytime of day or night by visiting Sky and Telescope’s Jupiter’s Moons site.

What’s inside Mars? We’ll need InSight to find out

This artist’s concept depicts the stationary NASA Mars lander known by the acronym InSight at work studying the interior of Mars with a probe to measure heat flowing through the planet’s crust. The solar cells provide power to the lander. The mission will be an international one with instruments provided by several different space agencies. Credit: NASA

We’ve photographed Mars from orbit, drilled into its surface and sniffed its atmosphere looking for clues on how a warmer, wetter world went cold and dry. Now it’s time to go deep.

NASA’s InSight Mars Lander just before propulsion pressure testing in a Lockheed Martin clean room. Credit: NASA/Lockheed Martin

In March 2016, NASA plans to launch the InSight Mission that will place a single lander on Mars to study its deep interior. Named InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport), it will land in September and spend the next two years investigating the planet’s interior to determine the makeup of the Martian core, the thickness of the the crust and the composition of the mantle, the broad zone of rock between crust and core.

Using the SEIS seismometer, we’ll learn about the number and distribution of marsquakes caused by both internal stresses and meteorite impacts. The information will also help us unravel the structure of Mars’ hidden interior just as the study of earthquakes here on Earth has taught us much about the internal structure of the ball beneath our feet. We know that Earth’s center is avocado-like with a solid inner core of iron-nickel surrounded by a softer, liquid outer core.

Artist concept of the interior of Mars. Mars has a low density compared to the other rocky planets leading astronomers to believe it has less iron in its core. The lack of a global magnetic field around the planet also suggests the core is solid. Currents within Earth’s liquid outer core are believed responsible for generating the planet’s magnetic field. Credit: NASA-JPL-Caltech

The lander packs a unique “mole” or heat probe that can hammer over 16 feet (5-meters) into the Martian crust, deeper than all previous drills, scoops, arms and probes, to learn how much heat flows from the planet’s interior. As the mole burrows down in the crust it will pull a tether of heat sensors along to measure the increase in temperature with depth. Heat flow sounds obscure but it’s critical in understanding where and how mountain ranges and volcanoes form.

Another experiment, the Rotation and Interior Structure Experiment or RISE, will use variations in the receive time of the lander’s radio signals to measure minute wobbles in Mars’ rotation axis that will tell us more about the size of the core and whether it’s solid or not.

InSight will land near Mars’ equator not far from the Curiosity Rover. Credit: NASA

Because Mars has been less geologically active than the Earth – it lacks plate tectonics that recycles and renews its crust – it actually retains a more complete record of its history in its own basic planetary building blocks of core, mantle and crust. Scientists hope that insights from InSight will help us understand the forces that shaped not only Mars but all the rocky planets across the solar system.

Three ancient volcanoes rise from the the giant bulge on Mars known as Tharsis in this Viking 1 image taken in 1980. From bottom to top: Arsia Mons, Pavonis Mons and Ascraeus Mons. It’s thought that Tharsis overlies an enormous hot spot where huge quantities of lava were released as long ago as 3.7 billion years to create both the bulge and volcanoes. The cracks may have formed from the weight of the overlying lavas. Credit: NASA

Don’t forget the cameras! InSight will carry a navigation camera similar to those on the the Mars rovers mounted on the lander’s arm. In addition to black and white panoramas, it will shoot photos of the instruments on the lander’s deck and a 3-D view of the ground where the seismometer and heat flow probe will be placed. Mission controllers will also use it to guide them in the placing of the instruments to the ground. A second wider angle camera like the hazcams on the rovers will provide a second perspective on the scene.

I don’t know about you, but I can never get enough Mars. I’m eager to see the mission underway.

Spectacular meteor storm lights up Mars during recent comet flyby

On October 19, when Comet C/2013 A1 Siding Spring flew just 87,000 miles from Mars, dust from its tail set the sky aglow with a meteor storm. This illustration is my feeble attempt to show what you might have seen standing on Mars next to the Curiosity rover at the time. Credit: NASA (background) with additions and changes by Bob King

Oh, to have stood under the Martian sky on October 19th! As Comet Siding Spring passed just 87,000 miles (140,000 km) from the planet that night, dust in its tail slammed into the Martian atmosphere at 126,000 mph, burning up in storm of meteoric madness. “Thousands per hour fell,” said Nick Schneider, instrument lead for NASA’s MAVEN Imaging Ultraviolet Spectrograph. It must have looked like those classic illustrations of the 1833 and 1866 Leonid meteor storm back here on Earth.

Composite image of Comet Siding Spring and Mars taken by the Hubble Space Telescope. The images have been added together to create a single picture to illustrate the true distance or separation (1/20th the apparent size of the Full Moon) between the comet and Mars at closest approach.  Credit: NASA/ESA

I participated in a teleconference yesterday with principal investigators for the instruments on the Mars Reconnaissance Orbiter (MRO), MAVEN and Mars Express spacecraft pressed into service to study Comet Siding Spring during its historic flyby. The comet is a visitor from the faraway Oort Cloud, a spherical repository of billions of icy comets up to 1 light year from the Sun. Some 4-5 Oort Cloud comets swing through the inner solar system every year; this is the first one we’ve ever studied up close. It was discovered at Siding Spring Observatory in Australia by Robert McNaught on January 13, 2013.

NASA’s MAVEN uses its IUVS to perform a scan of the Martian atmosphere along its limb. Scans found enhanced levels of metals from vaporizing comet dust. Credit: NASA

“Dust slammed into the atmosphere and changed the chemistry of the upper atmosphere,” said Jim Green, director, Planetary Science Division, NASA Headquarters in Washington. Data from MAVEN’s UltraViolet Spectrograph (IUVS), which scans of Mars’ upper atmosphere in UV light to determine its chemical makeup, saw big spikes in the amount of magnesium and iron during the flyby. These elements are commonly found in meteorites.

Before and after scans by MAVEN. At left is a profile of the atmosphere before the comet’s arrival showing carbon dioxide and other gases; at right is during the comet’s pass. Check out that huge spike to the right – that from magnesium. Elevated levels to the left indicate iron. Credit: NASA

Siding Spring turned out to be much dustier than expected, prompting Green to later add: “It makes me very happy hid them (spacecraft) on the backside of Mars.” “It really saved them. Even one well-placed hit from a high-speed dust particle could damage an instrument, and Siding Spring peppered the Martian atmosphere with “several tons” of dust.

MAVEN used its mass spectrometer – an instrument that identifies elements by how much mass they have – to record a big enhancement of the elements magnesium, manganese, iron and others from comet dust in Mars’ atmosphere. Credit: NASA

Meanwhile, MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS), picked up major spikes in 8 different metals from ablating comet dust including sodium, magnesium, iron and nickel. Jim Green pointed out that the increase in sodium may have tinged the twilight sky with a yellow glow. That and a recent increase in the amount of dust in the atmosphere over the Curiosity rover site may be the reason the comet was so difficult to photograph from the ground.

Only hours after Comet Siding Spring’s closest approach, dust particles hitting air molecules on Mars formed a temporary ionized (electrified) layer in its lower ionosphere 50-60 miles high. Credit: ESA

So we have a very dusty comet, a big meteor storm, the atmosphere spiced up with metals from burning dust.

Anything else? Heck, yes. The European Space Agency’s Mars Express Orbiter used its radar to send out radio waves of very low frequency down through Mars atmosphere to record the state of the ionosphere, a rarified layer of air between 60-250 miles (100-400 km) high. At the comet’s closest approach, the ionosphere was normal, but 7 hours later, impacting dust had created a brand new, temporary ionization layer.

Close-ups pictures taken by the Mars Reconnaissance Orbiter of Comet Siding Spring around the time of closest approach to Mars. They show the combined light of the tiny nucleus and much larger coma or comet atmosphere. Comet dust / rocks range in size from 1/1000 of a millimeter to 1 centimeter (~1/2-inch). Credit: NASA

The high resolution camera on the MRO photographed brightness variations in the comet’s light, nailing down its rotation period to 8 hours. But size-wise, we’re a little less clear. Estimates for the comet’s nucleus range from 984 feet to 1.2 miles (300-m to 2 km). For comparison, Comet 67P/Churyumov-Gerasimenko, currently orbited by Europe’s Rosetta spacecraft, is 1.5 miles (2.4 km) across.

Color variations in this photo by CRISM indicate different sized dust particles being ejected by the comet. Credit: NASA

Yet another instrument named CRISM (Compact Reconnaissance Spectrometer for Mars) made some intriguing measurements of the coma showing distinct differences in color – red here, blue there – indicating the comet is blowing out dust particles of different sizes.

As scientists continue to analyze the data collected by the fleet of space probes, we’ll see more papers and results soon. For now, the rare opportunity to study a comet up close from another planet was an unqualified success. You can listen to the replay of the hour-long conference HERE.

Beauty at 225 below – a visit to Mars’ south pole

Black and white photo taken on September 10th and released this week by the Mars Odyssey spacecraft showing ice layers at Mars’ south pole. The image is 10.5 miles (17 km) across. Credit: NASA/JPL/ASU

Beautiful, isn’t it? You’re looking at multiple layers of water and carbon dioxide ice mixed with dust built up over millions of years at the south pole of Mars. Each layer or “step” varies in thickness from about 30 to 100 feet; together they make a stack up to 2.3 miles (3.7 km) high.

Mars permanent south polar cap measures about 250 miles (400 km) and consists primarily of water ice. During the southern winter, carbon dioxide in Mars’ atmosphere condenses as frost and falls as snow, whitening the planet’s southern hemisphere to latitude 50º south. Much the same happens on Earth during the winter months when snow covers the ground to across the northern and central U.S. and Canada.

The layers in these cliffs show buried ice deposits in the southern polar region of Mars at about 72°S. The image was obtained by Mars Express on January 15, 2011. Credit: ESA/DLR/FU Berlin (G. Neukum)

With a difference. On Mars, where the average temperature is -70 F but can drop as low as -225 F at the poles, snowflakes are made of dry ice, conjuring up visions of astronauts shoveling their way out of a CO2 blizzard. As the planet warms during its summer seasons, most of the frost / snow vaporizes in the sunshine and the polar caps shrink back to their norms. While the seasonal covering is primarily carbon dioxide ice, both polar caps are primarily made of good, old-fashioned water ice.

A dust storm rages near the edge of Mars north polar region on May 24, 2002. Credit: NASA

The red tint you see in the Mars Express photo shows that each layer is far from pure ice but lined with dust. Every spring, solar heating vaporizes dry ice from the pole, stoking winds that whip up dust storms. Some storms are regional; others expand to enshroud the entire planet. Later in fall, as temperatures drop, those dust particles act as condensation nuclei or particles that coax chilled carbon dioxide to condense as snowflakes. Voila! Tinted snow.

Stacked like pancakes. Close up from orbit of layered ice and dust deposits at one of the Martian poles. Credit: NASA

Variations in Mars’ climate over millions of years changes the amounts of ice and dust deposited at the poles creating the beautiful swirly layers of white and orange. Just as the study of annual tree rings tell us about past environmental conditions, planetary scientists look to the Martian poles as repositories of the planet’s climate history. Someday we’ll drill ice cores there like we do from Earth’s glaciers.

Melting ice cream? No, this is a recent view of Mars’ south polar region taken by the ESA’s Mars Express spacecraft. Dust-stained ice is everywhere. The spiral pattern might be due to prevailing winds. Click to enlarge. Credit: ESA

Mars meets Kaus Borealis tonight

Mars passes very close to Kaus Borealis (a.k.a. Lambda Sagittarii) tonight. If your skies are clear, take a look during evening twilight about an hour after sunset low in the southwestern sky. Source: Stellarium

Just a quick heads up. I always like to report when a planet and star pair up in the night sky. That happens to happen tonight (Nov. 3) when Mars passes just 1/2° north of Kaus Borealis, the star at the top of the Teapot of Sagittarius.

To spy this temporary “double star”, go out about an hour after sunset and look low in the southwestern sky. That bright red-orange object is Mars. Immediately to its lower left, you’ll see Kaus Borealis deliciously close.

The sky facing southwest on Nov. 18, 1984 shortly before Venus occulted Kaus Borealis. The map shows the sky from Duluth, Minn. during evening twilight. Source: Stellarium

Kaus Borealis, a name combining the Arabic word for ‘bow’ and the Latin word for ‘northern’, refers to the bow of Sagittarius the Archer, the constellation’s formal name. At magnitude +2.8, the star is easy to spot with the naked eye. Since it lies near the ecliptic, the path followed by the Sun, Moon and planets, it’s occasionally occulted by one of these bodies. Back on the evening of November 18, 1984, Venus passed directly over the star and blanked from view for a time. What a scene! Not only did the star blank out, but Jupiter, the sky’s second brightest planet, shone nearby in the same constellation.

Mars won’t occult Kaus, but for a fun activity tonight and over the next few nights, compare the colors of Mars and the star. Kaus Borealis is an orange subgiant star (not quite as big as Arcturus, an orange giant) 2.3 times as massive as the Sun and 52 times brighter. Is Mars more red or are they nearly the same? Have fun getting acquainted with a star we might otherwise ignore were it not for Mars’ proximity.

Earth and Moon captured together in amazing new photo

Chang’e 5 took this splendid photo of Earth and Moon together while it passed over the lunar far side on October 28, 2014. The Moon reflects far less light than Earth and appears darker.  Click to grab a large version. Credit: CNSA / Xinhua News Agency

A friend alerted me to this wonderful photo of Earth and Moon in the same single image taken by China’s Chang’e 5 lunar test vehicle. The spacecraft is conducting an 8-day mission to the Moon and back to refine the technology needed for a planned sample return mission in 2017. Launched on October 23, this is China’s fourth volley to the Moon; the spacecraft will return to Earth on November 1 according to Xinhua News.

View of Earth taken by the Chang’e 5 test vehicle on October 28 after rounding the far side of the Moon. Australia is easy to see in the clearing. Credit: CNSA / Xinhua News Agency

As it swung high above the far side of the Moon – the hidden half of the lunar globe out of sight from Earth – the solar array monitoring camera on the craft snapped this incredible image. While not the first ever taken of the pair, it’s one of the best composed images and possibly the first to clearly feature the lunar far side along with Earth. You can easily see how much more cratered the Moon’s hidden hemisphere is. And that dark splotch? That’s Mare Moscoviense (Sea of Moscow), one of the very few dark maria or seas on the far side.

View of the Moon by Chang’e 5 on October 28 shows the dark lunar “sea” called Mare Marginis. This patch is visible along the western edge of the moon from Earth. Credit: CNSA / Xinhua News Agency

Chang’e 5 did not enter lunar orbit but kept its camera humming to shoot separate close-ups of Earth and Moon. Like seeing Earth and Moon from afar? Check these out:

Earth and Moon dance a pirouette in these images taken by the Jupiter-bound spacecraft Juno on Oct. 9, 2013

The European Space Agency’s Mars Express captured this image of Earth and the Moon on July 3, 2005 when it was 5 million miles ( 8 million km) away. Credit: ESA

Earth and Moon in 1992 as Galileo photographed the duo on its way to Jupiter. Credit: NASA

Earth is the brightest “star” in Mars’ western evening sky as seen and photographed by the Curiosity Rover on Jan. 31, 2014. Credit: NASA

A single frame from high-definition video of the full Earth over the lunar limb taken by Japan’s Kaguya spacecraft on April 6, 2008. Credit: JAXA/NHK

Earth and Moon from Mars, imaged by Mars Global Surveyor on May 8, 2003. Credit: NASA

Earth rises over the barren lunar landscape photographed by the Apollo 8 crew on December 24, 1968. Credit: NASA

Earth and Moon become a single dot in this photo taken by the Voyager 1 spacecraft from a distance of 4 billion miles (6.4 billion km) on February 14, 1990. Credit: NASA/JPL

Moon gives us a wink / Mars near and afar

Tonight (Oct. 25) the thin lunar crescent appears again at dusk low in the southwestern sky near the planet Saturn. This map shows the sky about 20 minutes past sunset. Source: Stellarium

After a splendid eclipse performance, the Moon returns at dusk this evening low in the southwestern sky after sunset. Reborn as a waxing crescent, it will slip away from the Sun in the coming days and gently light the night.

For those who like something much more challenging than spying the Moon, try finding Saturn about 3 degrees to its west. Binoculars required!

India’s Mars Orbiter tweeted this full-color photo of the planet earlier this month. It features the hemisphere of Mars rich in ancient volcanoes, the brown, circular structures that look like anthills.  The largest, Olympus Mons, is visible at far left center. The planet’s north polar region is covered in clouds. Credit: ISRO

Farther east, Mars, though low, is still an easy catch with the naked eye. Most of us gave up looking at it in a telescope several months ago, since the planet has shrunk to 5.6″ in diameter, not quite twice as big as Uranus’ apparent size. Mars is far from Earth and presently in in its “orange blip” phase. Even at 300x magnification, such a tiny disk shows little detail.

Little Phobos, only 10 by 14 by 11 miles (17 by 22 by 18 km), looks tiny indeed against the backdrop of the mother planet. Credit: ISRO

No matter. So many space probes now orbit the planet, close-up views are available at the click of a mouse. The Mars Orbiter Mission (MOM) has sent back some excellent color images of the planet recently including one showing Mars’ small moon Phobos in orbit.

Photos taken by the Mars Curiosity rover on June 28, 2013 show the moon Phobos rising in the Martian sky. White dots are hot pixels and flashes are cosmic rays. 

Another view of Phobos taken by ESA’s Mars Express. This small, dark moon orbits 5,826 miles (9,380 km) above the planet. Credit: NASA