Curiosity Rover Snaps Photos of Comet Siding Spring, Giant Sunspot and Mars-shine

NASA’s Curiosity Rover spends most of its time staring at the ground, but like humans, it looks up once in a while too. As reported earlier, NASA ground controllers pointed the rover’s Mast Camera (mastcam) skyward to shoot a series of photos of Comet Siding Spring when it passed closest to the Red Planet on October 19th.  Until recently, noise-speckled pictures available on the raw image site confounded interpretation. Was the comet there or wasn’t it?  In these recently released versions, the fuzzy intruder is plain to see, tracking from right to left across the field of view. 

Remember the monster sunspot group on bold display during last month's partial solar eclipse. It was the largest group of the current solar cycle. Here it is again - returning for a second time - as seen by Curiosity on November 10th. Credit: NASA/JPL-Caltech
Remember the monster sunspot group on bold display during last month’s partial solar eclipse? It was the largest group of the current solar cycle and largest recorded in 24 years. Here it is again (lower left) – returning for a second time – as seen by Curiosity on November 10th. Click for raw version. Credit: NASA/JPL-Caltech

Ten exposures of 25 seconds each were taken between 4:33 p.m. and 5:54 p.m. CDT on October 19th to create the animation.  The few specks you see are electronic noise, but the sharp, bright streaks are stars that trailed during the time exposure. Curiosity’s Mastcam camera system has dual lenses –  a 100mm f/10 lens with a 5.1° square field of view and a 34mm, f/8 lens with a 15° square field of view. NASA didn’t include the information about which camera was used to make the photos, but if I had to guess, the faster, wide-angle view would be my choice. Siding Spring was moving relatively quickly across the Martian sky at closest approach.

Sunspot region 2192 (lower left) has returned for an encore in this photo taken by NASA's Solar Dynamics Observatory. The same group is visible in images taken 4 days earlier from Mars. Credit: NASA/SDO
Sunspot region 2192 (lower left) has returned for an encore in this photo taken by NASA’s Solar Dynamics Observatory. The same group is visible in images taken 4 days earlier from Mars. Credit: NASA/SDO

Prowling through the Curiosity raw image files, I came across this photo of the Sun on November 10th. Three dark spots at the left are immediately obvious and a dead-ringer for Active Region 2192, now re-named 2209 as it rounds the Sun for Act II.  You’ll recall this was the sunspot group that nearly stole the show during the October 23rd partial solar eclipse. From Mars’ perspective, which currently allows Curiosity to see further around the solar “backside”, AR 2209 showed up a few days before it was visible from Earth.

Mars Earth line of sight nov 10 final V2
Because of Mars’ position relative to the Sun, Curiosity saw the return of sunspot group 2192 before it was visible from Earth. The Sun had to rotate about another 4 days to carry the group into Earth’s line of sight. Source: Solarsystemscope with additions by the author

Although it’s slimmed down in size, the region is still large enough to view with the naked eye through a safe solar filter. More importantly, it possesses a complex beta-gamma-delta magnetic field where magnetic north and south poles are in close proximity and ripe for reconnection and production of M-class and X-class flares. Already, the region’s crackled with three moderate M-class flares over the past two days. In no mood to take a back seat, AR 2209 continues to dominate solar activity even during round two.

Phobos is very small but big enough for someone on the surface to see its shape with the naked eye, especially when the moon is high in the sky and closest to the observer. Then, it spans 1/3 the diameter of our Moon. Credit: NASA/JPL-Caltech
Phobos is very small but orbits close enough for someone on the surface to see its shape with the naked eye, especially when it’s high in the sky and closest to the observer. Phobos is about 1/3 the size of our Moon. This photo was taken by Curiosity on October 20th and shows the moon’s largest crater, Stickney, at top.  Credit: NASA/JPL-Caltech with toning by the author to bring out details

Mars possesses two small moons, Deimos and Phobos. Curiosity has photographed them both before including an occultation Deimos (9 miles/15 km) by the larger Phobos (13.5 miles/22 km). Phobos orbits closer to Mars than any other moon does to its primary in the Solar System, just 3,700 miles (6,000 km). As a result, it moves too fast for Mars’ rotation to overtake it the way Earth’s rotation overtakes the slower-moving Moon, causing it to set in the west overnight. Contrarian Phobos rises in the western sky and sets in the east just 4 hours 15 minutes later. When nearest the horizon and farthest from an observer, it’s apparent size is just 0.14º. At the zenith it grows to 0.20º of 1/3 the diameter of the Moon.

Phobos occults Deimos in real time photographed by the Curiosity Rover on August 1, 2013. Credit: NASA/JPL-Caltech
Phobos occults Deimos in real time photographed by the Curiosity Rover on August 1, 2013. Credit: NASA/JPL-Caltech

One longish observing session on the planet would cover a complete rise-set cycle during which Phobos would first appear as a crescent and finish up a full moon a few hours later. All this talk about Phobos is only meant to direct you to the picture above taken by Curiosity on October 20, 2014 when the moon was a thick crescent. As on Earth, where Earthshine fills out the remainder of the crescent Moon, so too does Mars-shine provide enough illumination to see the full outline of Phobos.

Four-wheel drive only. Curiosity took this photo showing a sea of dark dune from the Pahrump Hills outcrop on November 13th. Credit: NASA/JPL-Caltech
Four-wheel drive only! Curiosity took this photo showing a sea of dark dunes from the Pahrump Hills outcrop on November 13th. Credit: NASA/JPL-Caltech

Curiosity has also photographed Earth, sunsets and transits of Phobos across the Sun while rambling across the dusty red landscape since August 2012. Before we depart, it seems only fair to aim our gaze Mars-ward again to see what’s up. Or down. The rover’s been doing a geological “Walkabout” in the Pahrump Hills outcrop at the base of Mt. Sharp in Gale Crater since September. Earlier this fall it drilled and sampled rock there containing more hematite than at any of its previous stops. Hematite is an iron oxide that’s often associated with water.

The mission may spend weeks or months at the outcrop looking for and drilling new target rocks before moving further up the geological layer cake better known as Mt. Sharp.

Mind-blowing Meteor Shower on Mars During Comet Flyby, Say NASA Scientists

“Thousands of meteors per hour would have been visible — truly astounding to the human eye.” That’s Nick Schneider’s description of what you and I would have seen standing on Mars during Comet Siding Spring’s close flyby last month. “It would have been really mind-blowing,” he added. Schneider is instrument lead for MAVEN’s Imaging Ultraviolet Spectrograph (IUVS).

He and a group of scientists who work as lead investigators for instruments on the MAVEN and  Mars Reconnaissance Orbiter (MRO) spacecraft shared the latest results from the comet flyby during a media teleconference earlier today. There were many surprises. Would we expect anything less from a comet?

Here’s a summary of the results:

A very dusty ice ball – The comet’s dust tail and the amount of dust in its coma were much larger than expected, prompting Jim Green, director of NASA’s Planetary Science Division in Washington,  to remark: “It makes me very happy we hid them (the spacecraft) on the backside of Mars. That really saved them.” Siding Spring dumped several tons of fine dust into the Martian atmosphere prompting a spectacular meteor shower and possibly causing a yellow, twilight afterglow above the Curiosity landing site from vaporizing sodium atoms contained in the minerals. That, and dust in the mid-levels of the atmosphere at the time contributed to the rover’s difficulty in getting good photos of the comet itself. Scientists are still examining the images.

MAVEN's Ultraviolet Imaging Spectrograph (IUVS) uses limb scans to map the chemical makeup and vertical structure across Mars' upper atmosphere. It detected strong enhancements of magnesium and iron from ablating incandescing dust from Comet Siding Spring. Credit: NASA
MAVEN’s Ultraviolet Imaging Spectrograph (IUVS) uses limb scans to map the chemical makeup and vertical structure across Mars’ upper atmosphere. It detected strong enhancements of magnesium and iron from ablating incandescing dust from Comet Siding Spring. Credit: NASA
I'm not big into graphs either, but check out the heavy metal drama in this. On the left is the "before" scan from MAVEN's IUVS instrument; on the right, during the comet's close approach. The spike in magnesium from vaporizing comet dust is impressive. Ionized magnesium is the strongest spike with neutral and ionized iron on the left in smaller amounts. Both elements are common in meteorites as well as on Earth. Credit: NASA
I’m not big into graphs either, but check out the heavy metal drama going on here. On the left is the “before” scan from MAVEN’s IUVS instrument; on the right, during the comet’s close approach. The spike in magnesium from vaporizing comet dust is impressive. Ionized magnesium is the strongest spike with neutral and ionized iron on the left in smaller amounts. Both elements are common in meteorites as well as on Earth. Credit: NASA
Profiles showing spikes in the amounts of eight different metals detected in Mars' atmosphere during the flyby by MAVEN's Neutral Gas and Ion Mass Spectrometer (NGIMS). The emissions faded with a short time. Credit: NASA
Profiles showing spikes in the amounts of eight different metals over time detected in Mars’ atmosphere by MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS). The emissions faded within a short time, but chemicals from the comet will continue to interact with the Martian atmosphere over time. Credit: NASA

Chemistry of Mars’ atmosphere changed – Dust vaporized in the intense meteor shower produced a striking increase in the amount of magnesium, iron and others metals in Mars’ upper atmosphere. “We were pressed back in our chairs,” said Mike Schneider. The bombardment created a temporary new layer of comet-tainted air and may have acted as condensation nuclei for the formation of high-altitude clouds. MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS) recorded huge spikes in the levels of eight different metals during the comet’s passage and then trailed off a day or so later. “They came to MAVEN as a free sample from no less than an Oort Cloud comet,” said Mehdi Benna, instrument scientist for MAVEN’s Neutral Gas and Ion Mass Spectrometer.

The MARSIS instrument on the Mars Express is a ground penetrating radar sounder used to look for subsurface water and ice. It can also make soundings of the ionosphere. It was used to see the new ionospheric layer formed by vaporizing comet dust on October 19th. Credit: ESA
The MARSIS instrument on the Mars Express is a ground penetrating radar sounder used to look for subsurface water and ice. It can also make soundings of the ionosphere. It was used to see the new ionospheric layer formed by vaporizing comet dust on October 19th. Credit: ESA
The Mars Express radar probed the ionosphere (upper atmosphere) at three different times. At top, before the comet arrived; middle, 7 hours later after the comet's closest approach and bottom, hours later after the comet had departed. The middle graph shows a strong signal (blue horizontal bar) from the creation of newly-ionized layer of the planet's lower atmosphere from hot, fast-moving comet dust. Credit: ESA
The Mars Express radar probed the ionosphere (upper atmosphere) at three different times. At top, before the comet arrived; middle, 7 hours later after the comet’s closest approach and bottom, hours later after the comet had departed. The middle graph shows a strong signal (blue horizontal bar) from the creation of a newly-ionized layer of the planet’s lower atmosphere from hot, fast-moving comet dust. Credit: ESA

 

Flaming comet dust creates new ionospheric layer – Comet dust slamming into the atmosphere at 125,000 mph (56 km/sec) knocked electrons loose from atoms in the thin Martian air  50-60 miles (80-100 km) high, ionizing them and creating a very dense ionization layer in the planet’s lower ionosphere seven hours after the comet’s closest approach. Normally, Mars ionosphere is only seen on the dayside of the planet, but even when the MARSIS instrument on Mars Express  beamed radio waves through the atmosphere on the nightside of the planet, it picked up a very strong signal.

54 red-filtered images of the comet's nucleus-coma taken by the MRO's HiRISE camera show changes in the flow of material leaving the comet. Credit: NASA
54 red-filtered, false-color images of the comet’s nucleus-coma taken by the MRO’s HiRISE camera show changes in the flow of material leaving the comet. Based on the photos, the comet’s nucleus spins once every 8 hours. Credit: NASA
The five closest photos made with the HiRISE camera show the combined light of the nucleus and coma. Scale is 140-meter per pixel at top and 177-meters at bottom. Scientists will further process these images to separate the nucleus from the coma. Credit: NASA
The five closest photos made with the HiRISE camera show the combined light of the nucleus and coma. Scale is 140-meter per pixel at top and 177-meters at bottom. Scientists will further process these images to separate the nucleus from the coma. Credit: NASA

Nucleus spins once during your work day – Comet Siding Spring’s icy core spins once every 8 hours and its irregular shape causes strong variations in the comet’s brightness. The comet’s size appears less certain  – at least for the moment – with estimates anywhere between a few hundred meters to 2 km (1.2 miles). More analysis on images taken by MRO’s HiRISE camera should narrow that number soon.

CRISM photo and spectrum of Comet Siding Spring. The spectrum is "flat", indicating we're seeing sunlight reflected off comet dust. The intriguing color variations in the image tell of dust particles of varying size leaving the nucleus. Credit: NASA
CRISM photo and spectrum of Comet Siding Spring. The spectrum is “flat”, indicating we’re seeing ordinary sunlight reflecting off comet dust. The intriguing color variations in the image tell us the comet’s spewing dust particles of many sizes. Credit: NASA

Dust motes of many sizes – Color variations across Siding Spring’s coma seen by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) indicate it’s releasing dust particles of different sizes – big and little.

The scientists involved in the encounter couldn’t be happier with how the instruments functioned and the amount of hard data returned. Said Jim Green: “We are so lucky to observe this once-in-a-lifetime event.” How true when you consider that it takes about 8 million years for a comet from the Oort Cloud, that vast reservoir of frozen comets  extending nearly a light year from the Sun, to get here in the first place.  Nick Schneider put it another way:

“Not only is this a free sample of the Oort Cloud in Mars’ atmosphere, but it gives us a chance to learn more about Mars itself.”

If you’d like to listen in to the hour-long teleconference at any time, it’ll be up for the next week or so HERE.

MRO Spies Tiny, Bright Nucleus During Comet Flyby of Mars

Not to be outdone by the feisty Opportunity Rover, the HiRISE camera on NASA’s Mars Reconnaissance Orbiter (MRO) turned in its homework this evening with a fine image of comet C/2013 Siding Spring taken during closest approach on October 19. 

The highest-resolution images were acquired by HiRISE at the minimum distance of 85,750 miles (138,000 km). The image has a scale of 453 feet (138-m) per pixel.

The top set of photos uses the full dynamic range of the camera to accurately depict brightness and detail in the nuclear region and inner coma. Prior to its arrival near Mars astronomers estimated the nucleus or comet’s core diameter at around 0.6 mile (1 km). Based on these images, where the brightest feature is only 2-3 pixels across, its true size is shy of 1/3 mile or 0.5 km. The bottom photos overexpose the comet’s innards but reveal an extended coma and the beginning of a tail extending to the right.

Annotated photo of Comet Siding Spring taken by the Opportunity Rover on October 19 when near closest approach. Credit: NASA/JPL-Caltech/Cornell Univ./ASU/TAMU
Annotated photo of Comet Siding Spring taken by the Opportunity Rover on October 19 when near closest approach. Credit: NASA/JPL-Caltech/Cornell Univ./ASU/TAMU

To photograph a fast-moving target from orbit, engineers at Lockheed-Martin in Denver precisely pointed and slewed the spacecraft based on comet position calculations by engineers at JPL. To make sure they knew exactly where the comet was, the team photographed the comet 12 days in advance when it was barely bright enough to register above the detector’s noise level. To their surprise, it was not exactly where orbital calculations had predicted it to be. Using the new positions, MRO succeeded in locking onto the comet during the flyby. Without this “double check” its cameras may have missed seeing Siding Spring altogether!

Meanwhile, the Jet Propulsion Lab has released an annotated image showing the stars around the comet in the photo taken by NASA’s Opportunity Rover during closest approach. From Mars’ perspective the comet passed near Alpha Ceti in the constellation Cetus, but here on Earth we see it in southern Ophiuchus not far from Sagittarius.

Comet Siding Spring continues on its way today past the planet Mars in this photo taken on October 20. Copyright: Rolando Ligustri
Comet Siding Spring continues on its way today past the planet Mars in this photo taken on October 20. Copyright: Rolando Ligustri

“It’s excitingly fortunate that this comet came so close to Mars to give us a chance to study it with the instruments we’re using to study Mars,” said Opportunity science team member Mark Lemmon of Texas A&M University, who coordinated the camera pointing. “The views from Mars rovers, in particular, give us a human perspective, because they are about as sensitive to light as our eyes would be.”

After seeing photos from both Earth and Mars I swear I’m that close to picturing this comet in 3D in my mind’s eye. NASA engineers and scientists deserve a huge thanks for their amazing and successful effort to turn rovers and spacecraft, intended for other purposes, into comet observatories in a pinch and then deliver results within 24 hours. Nice work!

Opportunity Rover Spots Comet Siding Spring from the Surface of Mars!

It looks like NASA’s hard-working Opportunity Rover nabbed our very first pictures of a comet seen from another world!  A study of raw images taken by the rover turned up a very promising fuzzy object. Only three night sky pictures were posted today, but two clearly show a fuzzy spot near the center of the field. Stars show as points of light and there are what appear to be a smattering of cosmic ray hits, but in the photo above, the brightest object is slightly elongated (trailed during the exposure?) and cometary in appearance. 

Here’s another photo:

A second picture from Opportunity possibly showing the comet. Click for original. Credit: NASA/JPL-Caltech
A second picture from Opportunity possibly showing the comet. Click for original. Credit: NASA/JPL-Caltech

Looking back over earlier photos of the sky taken on Sol 3212 show only stars and no fuzzy blobs. The pictures were taken around 4:13 a.m. local time with the Sun 25 degrees below the horizon. Opportunity can photograph diffuse objects as dim as the Andromeda Galaxy at magnitude +3.5 and stars down to magnitude +6 or +7. That’s similar to what we see on Earth on very dark night. Since the comet glowed far brighter at around magnitude -5 by some estimates, it would be a relatively easy catch for the rover panoramic camera.

Curiousity Navcam photo of the sky on October 19, 2014. Credit: NASA/JPL-Caltech
Curiousity Navcam photo of the sky on October 19, 2014, shows the silhouetted rim of Gale Crater and lots of noise. Credit: NASA/JPL-Caltech

NASA has also posted images taken by the Curiosity Rover but for the life of me I can’t find any sign of the Comet Siding Spring. Maybe it’ll pop out after the noise is removed. We’ll keep you posted.

Another Curiosity photo of the sky. If you look closely you'll see stars among the noise. Click for original Credit: NASA/JPL-Caltech
Another Curiosity photo of the sky. If you look closely you’ll see stars among the noise. Click for original Credit: NASA/JPL-Caltech

 

Astrophotographers Capture Dramatic Photos of Comet Siding Spring Approaching Mars

Astrophotographer Damian Peach shares this spectacular image of comet C/2013 A1 Siding Spring approaching Mars taken just hours ago.  The faint comet shows a small, condensed coma and bent tail against the glaring orange glow of the brilliant planet. Most photos of comets passing by a planet or deep sky object are lucky line-of-sight pairings with the comet in the foreground and object light years away in the background. Not this one. Both Siding Spring and Mars lie at nearly the identical distance from Earth of 151 million miles (243 million km).  

Artist view of the comet passing closest to Mars this Sunday. At the time, the Mars orbiters from the U.S., Europe and India will be huddled on the opposite side of the planet to avoid possible impacts from comet dust. Credit: NASA
Artist view of the comet passing closest to Mars this afternoon October 19. At the time, the Mars orbiters from the U.S., Europe and India will be huddled on the opposite side of the planet to avoid possible impacts from comet dust. Credit: NASA

When closest to Mars this afternoon, Siding Spring is expected to shine at around magnitude -5 or about twice as bright as Venus. Mind you, that estimate considers the entire comet crunched down into a dot. But for those who remember, Comet Hale-Bopp remained at zero magnitude, 100 times fainter than Siding Spring, and made for one of the most impressive naked eye sights on spring evenings in 1997.

More recently, Comet McNaught climaxed at magnitude -5 in the daytime sky near the Sun in January 2007. It was plainly visible in binoculars and telescopes in a blue sky  if you knew exactly where to look and took care to avoid the Sun. Would-be Martians are far more fortunate, with Siding Spring appearing high overhead in a dark sky from some locations, including that of NASA’s Curiosity Rover.


Comet C/2013 Siding Spring as it rises and sets over the Curiosity Rover this weekend October 18-19. Credit: Solarsystemscope.com

Right on time for today’s encounter, the folks at Solarsystemscope.com have rolled out an interactive simulation of Comet Siding Spring’s appearance in the sky above Curiosity. Just click the play button on the control panel above to run it live. Seen from Mars, the comet bobs along Eridanus the River southwest of Orion, passing high in the southern sky overnight. What a sight!

Another photo, just in, taken of the comet and Mars today by Rolando Ligustri. Beautiful!
Another photo, just in, taken of the comet and Mars today by Rolando Ligustri. Beautiful!

The comet nucleus is only about 0.4 miles (700 meters) across, but the coma or atmosphere fluffs out to around 12,000 miles (19,300 km). Seen from the ground, Siding Spring would span about 8°of sky or 16 full Moons from head to tail. Moving at 1.5° per minute, we could watch crawl across the heavens in real time with the naked eye. Wish I zoom to Mars for a look, but the rovers and orbiters will be our eyes as they study and photograph the comet during its brief flyby. As soon as those pictures become available, we’ll publish them here. Can’t wait!


Come Siding Spring comes out the other side!

While we’re waiting, amateur astronomers have been busy shooting additional photos and creating videos from their images. Fritz Helmut Hemmerich made this video from 1200-meters at Tenerife in the Canary Islands showing Comet Siding Spring immediately after its Mars encounter. One thing we know for certain is that the comet is intact after its close brush.

Negative image showing Comet Siding Spring closely approaching Mars today. Credit: Peter Lake
Negative image showing Comet Siding Spring closely approaching Mars today. Credit: Peter Lake

And find our more amazing photos and information at Sen TV, and you can follow them on Twitter at @sen.

Watch Live as Comet Siding Spring Flys By Mars

Comet Siding Spring will pass close to Mars today, Sunday, October 19, at 18:32 UTC. The comet will come within 139,500 km (87,000 miles) of the Red Planet, which is sixteen times closer to Mars than any known comet has ever come to Earth. About 100 minutes after the closest approach, the densest part of the comet’s tail will pass Mars’ location. You can watch live below courtesy of Slooh, ESA and the Virtual Telescope, below:

Slooh will feature two shows. The first show, billed “Close Call – Comet Siding Spring Zips by Mars,” will start at 11:15 AM PDT / 2:15 PM EDT / 18:15 UTC – International times here where Slooh will track Comet Siding Spring on close-approach live from South Africa and later from the Canary Islands. The second show, billed “Comet Siding Spring – the Outcome” will start at 5:30 PM PDT / 8:30 PM EDT / 00:30 UTC (10/20) – International times here – where Slooh will continue to track the comet live from Slooh’s southern observatory located at the Catholic University (PUC) – both shows will feature expert commentary by esteemed astrobiologist David Grinspoon and Slooh host Geoff Fox. The latter show will feature a special discussion with Slooh astronomer Bob Berman, who will be on location in Chile. Viewers can ask questions during each show by using hashtag #SloohComet.

Here’s ESA’s livestream:

Watch live streaming video from eurospaceagency at livestream.com

Also, Gianluca Masi’s Virtual Telescope: streaming begins Sunday, Oct. 19 at 11:45 a.m. CDT (16:45 UT)

Here’s a Look at Comet Siding Spring Two Days Before its Encounter with Mars

The excitement continues to build as Comet Siding Spring rapidly approaches the Red Planet, and here’s the latest view of the comet from prolific astrophotographer Damian Peach. While Comet Siding Spring’s encounter with Mars on October 19 will not be visible from Earth with the unaided eye, skywatchers in mid-northern latitudes, can now view the comet; an 8-inch (20 cm) or larger telescopes is needed to follow the comet as it travels from Scorpius north to Ophiuchus and its encounter with Mars on October 19.

The comet will come within 139,500 km (86,000 miles) above the planet’s surface on Sunday.

In Depth: How to See Comet Siding Spring as it Encounters Mars

Below, see a really nice animation put together by Kevin Gill of the path the comet will take past Mars.

An animation of the approach of the comet C/2013 A1 Siding Spring on Mars over the next few days. Credit: Kevin Gill.
An animation of the approach of the comet C/2013 A1 Siding Spring on Mars over the next few days. Credit: Kevin Gill.

Kevin said on G+ that his animation is based on vector ephemeris from the JPL Horizons system.

As our David Dickinson discussed earlier this week, if you were an astronaut stranded on the surface of Mars, the comet’s passage would be a spectacular sight under the dark Martian sky. Some scientists suggest it could even spawn a short but brilliant meteor shower caused by cometary dust grains plunging into the Martian atmosphere.

The spacecraft in orbit around Mars will be watching Comet Siding Spring too. The fleet of spacecraft from ESA, NASA and ISRO will hide behind the Red Planet on Sunday morning, trying to avoid possible bombardment by tiny grains of dust from the comet. But before and after that, the spacecraft will attempt to gather data on the comet as well as try to measure how the gas and dust interact with the Martian atmosphere.

Stay tuned for news on the comet’s encounter with Mars.

How to See Comet Siding Spring as it Encounters Mars

With excitement building as Comet Siding Spring rapidly approaches the Red Planet, we’ll soon have the opportunity to spot it through our own telescopes. Dark skies return this week with the moon now past full and rising later each night. Until recently, the comet could only be seen by skywatchers living in southern latitudes. Now it’s popped high enough above the southern horizon to see from mid-northern latitudes, albeit low in the sky. Observers with 8-inch (20 cm) or larger telescopes can follow the comet as it travels from Scorpius north to Ophiuchus and its encounter with Mars on October 19. 

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JPL Horizons light curve for Comet C/2013 A1 Siding Spring shows it brightening as it approaches Earth and then fading after late September. For our purposes we’re interested in the purple squares which are visual magnitude estimates of the whole comet submitted to the Comet Observation Database. Recently, the comet has faded faster than predictions. Click for more details. Credit: CIOC

Until late September, the comet had been brightening as forecast based on the simple principle that the closer an object is to Earth the brighter it appears in the sky. Siding Spring came just shy of 1 A.U. of Earth in early September and has since been slip-sliding away. All through the first weeks of September it glowed at magnitude +9-10 and could be spotted in small telescopes trekking across the south polar constellations. Now on the cusp of its big moment with Mars, Siding Spring has been fading faster than expected.

It could be running low on exposed ice or concluding a long, slow outburst. Maybe it’s as simple as our changing perspective on the comet’s tail – we see it from the side now instead of looking down the tail where reflective dust piles up along our line of sight. No one knows exactly why, but given that comets are famous for their unpredictability due to their fragile nature and the varying rates at which they sputter away ice and dust, we shouldn’t be too surprised.

The paths of Mars and Comet Siding Spring are clearly on a (near) collision course! Watch over the coming nights as they draw ever closer. Source: Chris Marriott's SkyMap
The paths of Mars and Comet Siding Spring are clearly on a (near) collision course! Watch over the coming nights as they draw ever closer. This map shows the sky facing southwest at nightfall from Kansas City, Missouri. From the central U.S. the comet will be about 13-15º high but only ~5-8º altitude in the northern border states. Source: Chris Marriott’s SkyMap

So what does that mean for observers? The most recent observations put the comet at about magnitude +11 with a loosely condensed coma and diameter of about one arc minute or a little larger than Jupiter appears in a telescope. It’s a small, relatively faint object now but should be visible in 8-inch and larger telescopes from a dark sky assuming it doesn’t “drop off the deep end” and fade even faster.  With Mars nearby, finding the general location of Siding Spring is easy. The maps will help you pinpoint it.

Daily positions of Comet Siding Spring October 10-20 from the central U.S. at nightfall. Stars shown to magnitude +11.5. Closest approach to Mars is October 19. Brighter stars like 3 Sagittarii, 44 and 51 Ophiuchi and Theta Ophiuchi are labeled. Source: Chris Marriott's SkyMap
Daily positions of Comet Siding Spring October 10-20 from the central U.S. at nightfall. Stars shown to magnitude +11.5. Closest approach to Mars is October 19. The brighter stars 3 Sagittarii, 44 and 51 Ophiuchi and Theta Ophiuchi are labeled. Click for large version to print and use at the telescope. Source: Chris Marriott’s SkyMap

The good news is that the comet is heading straight north and getting higher in the sky every night. The bad news is that it’s also dropping westward each evening mostly negating its northerly altitude gains. Those in the southern U.S. will have the best viewing window with Siding Spring 20º high at nightfall (14º in the central states and 6º in the north). To ensure success, find a spot with a wide open view as far down to the southwestern horizon as possible. You’ll make best use of your time and see the comet highest if you set up during evening twilight and begin searching as soon as the sky is dark. Given that Mars is 1st magnitude and the comet has faded more than expected, it may be difficult to see against the planet’s glare on the 19th. Not that I want to dissuade you from trying, but the nights leading up to and after the encounter will prove better for comet spotting.

Need to get in closer yet? This map shows Mars and Comet Siding Spring on five nights closer to its flyby with stars to magnitude +12. Time and location are the same as the map above. Click for larger version. Source: Chris Marriott's SkyMap
Need to get in closer? This more detailed map shows Mars and Comet Siding Spring nightly October 15-20 with stars to magnitude +12. Time and location are the same as the map above. Click for larger version. Source: Chris Marriott’s SkyMap

The fluffball passed the glittery Butterfly Cluster (M6) in Scorpius on October 9 displaying an attractive curved tail pointing southeast. Tim Reyes of Universe Today calculated the current tail length at ~621,000 miles (1 million km) with a coma ~19,900 miles across (32,000 km).  Closest approach occurs around 1:28 p.m. Central Daylight Time (18:28 UT) October 19 when the comet will miss Mars by only 88,000 miles (141,600 km). Dust particles leaving the coma will rip by the planet at ~125,000 mph (56 km/sec). Will they pass close enough to set the Martian sky a-sparkle with meteors?

Not only will the Mars orbiters gather information about the comet and its dust before, during and after the encounter, a fleet of additional telescopes will be making the most of the rare opportunity. Credit: NASA
Not only will the Mars orbiters gather information about the comet and its dust before, during and after the encounter, a fleet of additional telescopes will make the most of the rare opportunity. Credit: NASA

According to a recent NASA press release, the period of greatest risk to orbiting spacecraft will start about 90 minutes after the closest approach of the comet’s nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the comet’s nucleus. Since the comet will barely graze the planet, dust impacts on orbiting spacecraft may or may not happen.

Back on Earth we can watch the daredevil pass by telescope or catch it live on the Web here:

* SLOOH:  broadcast begins Sunday Oct. 19 at 9:51 a.m. CDT (14:51 UT)

* Gianluca Masi’s Virtual Telescope:  streaming begins Sunday, Oct. 19 at 11:45 a.m. CDT (16:45 UT)

Memory Problems Plague Martian Rover Opportunity As It Prepares To Watch A Comet Pass By

NASA’s Opportunity rover is still experiencing frequent memory resets as it roams the Martian terrain near Endeavour Crater, even though the agency performed a reset a few weeks ago.

Officials, however, say the rover is healthy otherwise and ready for its next science goals: reaching a small crater dubbed Ulysses, and watching a comet pass by Mars in mid-October.

Opportunity is approaching its eleventh anniversary of working on Mars this coming January. The hardy rover has driven 25.34 miles (40.78 kilometers) as of late September, almost a marathon’s worth of exploration. Its original mandate was to last just 90 Earth days on Mars.

In late August, however, science was getting derailed because the aging rover’s Flash memory experienced frequent resets. This kind of memory stores information even while the rover is turned off. NASA did a reformat from afar and said at the time that the procedure worked perfectly, but in the weeks since Opportunity has experienced several resets. The agency is investigating what to do next.

Tracks from the Curiosity rover across Martian terrain on Sol 3,798 in October 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
Tracks from the Curiosity rover across Martian terrain on Sol 3,798 in September 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

NASA’s Opportunity update archive reports memory resets on Sept. 17, 20, 22, 23, 24 and 26. The agency is calling these events “benign” and the rover is performing drives and science amid the issues.

Among its work, in late September the rover did a twilight test of its panoramic camera to get ready for observations of Comet Siding Spring, which is skimming the Red Planet on Oct. 19, 2014.

On the surface, the rover has been examining ejecta of the small crater Ulysses and doing close-up observations of a rock surface nicknamed “Hoover”. Opportunity’s long-term science goal is to reach a zone dubbed Marathon Valley, where there could be clay minerals that formed in water.