New Horizons Archives

July 12, 2015December 23, 2015 by Ken Kremer

Charon Up Close Reveals Colossal Chasms and Craters: 1 Day and 1 Million Miles Out from Pluto Flyby

Chasms, craters, and a dark north polar region are revealed in this image of Pluto’s largest moon Charon taken by New Horizons on July 11, 2015. The annotated version includes a diagram showing Charon’s north pole, equator, and central meridian, with the features highlighted. Credits: NASA/JHUAPL/SWRI
Story/imagery updated[/caption]

In the final days before humankinds first ever flyby of mysterious and tantalizing Pluto for the history making up close visit on Tuesday, July 14, NASA’s New Horizons spacecraft has just delivered the sharpest and most stunning view yet of its binary companion Charon – and unveiled it to be a geologically rich world with colossal chasms, a multitude of craters and a humongous dark splotch in the northern regions. It’s obviously quite different in appearance and varies in composition from its larger planetary host.

Indeed the largest of Charon’s chasms stretches farther than Earth’s Grand Canyon. And it’s taken New Horizons over nine years speeding through space – since launching back in 2006 as the fastest spacecraft departing Earth – to get close enough to see these wonders for the first time.

“The most pronounced chasm, which lies in the southern hemisphere, is longer and miles deeper than Earth’s Grand Canyon,” says William McKinnon, deputy lead scientist with New Horizon’s Geology and Geophysics investigation team, in a NASA statement.

To put that into perspective, consider this; Charon is only about 750 miles (1200 kilometers) across, about half the diameter of Pluto. The Grand Canyon stretches 277 miles (446 km) across the western United States and is up to 18 miles (29 km) wide and attains a depth of over a mile (6093 feet or 1857 meters). Thus Charon’s ‘Grand Canyon’ is truly gargantuan in comparison to its moons size when compared to our Grand Canyon.

At 1471 miles (2368 km) across, Pluto is about half the diameter of the United States. Both Pluto and Charon and largely composed of icy materials, with much less rock compared to the terrestrial planets like Earth.

“This is the first clear evidence of faulting and surface disruption on Charon,” says McKinnon, who is based at the Washington University in St. Louis.

“New Horizons has transformed our view of this distant moon from a nearly featureless ball of ice to a world displaying all kinds of geologic activity.”

Chasms, craters, and a dark north polar region are revealed in this image of Pluto’s largest moon Charon taken by New Horizons on July 11, 2015. Credits: NASA/JHUAPL/SWRI

The exquisite new image of Charon’s chasms and canyons was just released by NASA this evening, Sunday, July 12. It was taken yesterday, Saturday, July 11, by New Horizons Long Range Reconnaissance Imager (LORRI) at a distance of 2.5 million miles (4 million kilometers) from Pluto and Charon, and radioed back to Earth today.

The largest crater seen in the July 11 images lies near Charon’s south pole and is about 60 miles (96.5 kilometers) across.

“The brightness of the rays of material blasted out of the crater suggest it formed relatively recently in geologic terms, during a collision with a small body some time in the last billion million years,” says the team.

“The darkness of the crater’s floor is especially intriguing,” says McKinnon.

“One explanation is that the crater has exposed a different type of icy material than the more reflective ices that lie on the surface. Another possibility is that the ice in the crater floor is the same material as its surroundings but has a larger ice grain size, which reflects less sunlight. In this scenario, the impactor that gouged the crater melted the ice in the crater floor, which then refroze into larger grains.”

New Horizons is now merely one day and one million miles (1.6 million km) out from its history making encounter with the Pluto planetary system – some three billion miles (4.8 billion km) from Earth. It passed the million mile milestone at 11:23 p.m. EDT, Sunday night July 12.

And its closing in fast on its quarry at a whopping 31,000 mph (49,600 kph) after a nine year interplanetary voyage.

The high resolution LORRI imager is achieving an image resolution of 5 mile per pixel at this moment at a million miles away. And it will gets thousands of times better during the closest approach.

“Features as small as the lakes in New York’s Central Park and wharfs on the Hudson will be resolved,” said New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado, during a live mission update today, July 12. The image resolution will reach a maximum of about 230 feet (70 meters).

New Horizons suite of seven science instruments will collected 44 gigabits of data during the flyby encounter period lasting from July 7 to July 16, from Pluto, Charon and the four tiny moons – Hydra, Styx, Nix and Kerberos.

New Horizons will swoop to within about 12,500 kilometers (nearly 7,750 miles) of Pluto’s surface and about 17,900 miles (28,800 kilometers) from Charon during closest approach at approximately 7:49 a.m. EDT (11:49 UTC) on July 14.

Pluto and Charon are gravitationally locked with an orbital period of 6.4 days, so they always show the same face to one another. They orbit about 12,160 mi (19,570 kilometers) apart but about a center of gravity, or barycenter, above the surface of Pluto, unlike any of the other major bodies in our solar system.

Image of Pluto and Charon from July 8, 2015; color information obtained earlier in the mission from the Ralph instrument has been added. Credits: NASA-JHUAPL-SWRI

Charon is by far the largest of Pluto’s five moons. The new July 11 image also shows that it sports a “mysterious dark region” stretching some 200 miles across near the north pole.

Pluto is the last of the nine classical planets to be explored up close and completes the initial the initial reconnaissance of the solar system nearly six decades after the dawn of the space age. It represents a whole new class of objects known as the ice dwarfs, located in the Kuiper Belt – a relic of solar system formation replete with countless bodies.

It has been three decades since we last visited planetary bodies at the outer reaches of our solar system when Voyager 2 flew past Uranus and Neptune in 1986 and 1989.

New Horizons trajectory to the Pluto System. Credit: NASA

The New Frontiers spacecraft was built by a team led by Stern and included researchers from SwRI and the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. APL also operates the New Horizons spacecraft and manages the mission.

Watch for Ken’s continuing onsite coverage of the Pluto flyby on July 14 from the Johns Hopkins University Applied Physics Laboratory (APL).

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

July 12, 2015December 23, 2015 by Bob King

Pluto’s Time to Shine Just Hours Away – A Guide and Timetable

Graphic showing New Horizons' busy schedule before and during the flyby. Credit: NASA

Countdown to discovery! Not since Voyager 2’s flyby of Neptune in 1989 have we flung a probe into the frozen outskirts of the Solar System. Speeding along at 30,800 miles per hour New Horizons will pierce the Pluto system like a smartly aimed arrow.

Pluto as seen from New Horizons on July 11, 2015. Credits: NASA/JHUAPL/SWRI — Newest view of Pluto seen from New Horizons on July 11, 2015 shows a world that continues to grow more fascinating and look stranger every day. See annotated version below.
Credits: NASA/JHUAPL/SWRI

On July 11, 2015, New Horizons captured a world that is growing more fascinating by the day. For the first time on Pluto, this view reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater. Rotating into view is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach on July 14. The annotated version includes a diagram indicating Pluto’s north pole, equator, and central meridian. Credits: NASA/JHUAPL/SWRI — For the first time on Pluto, this view reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater. Rotating into view is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach on July 14. The annotated version includes a diagram indicating Pluto’s north pole, equator, and central meridian.
Credits: NASA/JHUAPL/SWRI

Edging within 7,800 miles of its surface at 7:49 a.m. EDT, the spacecraft’s long-range telescopic camera will resolve features as small as 230 feet (70 meters). Fourteen minutes later, it will zip within 17,930 miles of Charon as well as image Pluto’s four smaller satellites — Hydra, Styx, Nix and Kerberos.

This image shows New Horizons' current position (3 p.m. EDT July 12) along its planned Pluto flyby trajectory. The green segment of the line shows where New Horizons has traveled; the red indicates the spacecraft's future path. The Pluto is tilted up like a target because the planet's axis is tipped 123° to the plane of its orbit. Credit: NASA/JHUAPL/SWRI — This image shows New Horizons’ current position (3 p.m. EDT July 12) along its planned Pluto flyby trajectory. The green segment of the line shows where New Horizons has traveled; the red indicates the spacecraft’s future path. The Pluto system is tilted on end because the planet’s axis is tipped 123° to the plane of its orbit. Credit: NASA/JHUAPL/SWRI

After zooming past, the craft will turn to photograph Pluto eclipsing the Sun as it looks for the faint glow of rings or dust sheets illuminated by backlight. At the same time, sunlight reflecting off Charon will faintly illuminate Pluto’s backside. What could be more romantic than Charonshine?

Six other science instruments will build thermal maps of the Pluto-Charon pair, measure the composition of the surface and atmosphere and observe Pluto’s interaction with the solar wind. All of this will happen autopilot. It has to. There’s just no time to send a change instructions because of the nearly 9-hour lag in round-trip communications between Earth and probe.

Instruments New Horizons will use to characterize Pluto are REX (atmospheric composition and temperature; PEPSSI (composition of plasma escaping Pluto's atmosphere); SWAP (solar wind); LORRI (close up camera for mapping, geological data); Star Dust Counter (student experiment measuring space dust during the voyage); Ralph (visible and IR imager/spectrometer for surface composition and thermal maps and Alice (composition of atmosphere and search for atmosphere around Charon). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — Instruments New Horizons will use to characterize Pluto are REX (atmospheric composition and temperature); PEPSSI (composition of plasma escaping Pluto’s atmosphere); SWAP (solar wind studies); LORRI (close up camera for mapping, geological data); Star Dust Counter (student experiment measuring space dust during the voyage); Ralph (visible and IR imager/spectrometer for surface composition and thermal maps) and Alice (composition of atmosphere and search for atmosphere around Charon). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Want to go along for the ride? Download and install NASA’s interactive app Eyes on Pluto and then click the launch button on the website. You’ll be shown several options including a live view and preview. Click preview and sit back to watch the next few days of the mission unfold before your eyes.

American astronomer Clyde Tombaugh discovered Pluto in 1903 from Lowell Observatory. Tombaugh died in 1997, but an ounce of his ashes, affixed to the spacecraft in a 2-inch aluminum container. "Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's 'third zone.' Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde Tombaugh (1906-1997)" — American astronomer Clyde Tombaugh discovered Pluto in 1930 from Lowell Observatory. Tombaugh died in 1997, but an ounce of his ashes, affixed to the spacecraft in a 2-inch aluminum container. “Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system’s ‘third zone.’ Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde Tombaugh (1906-1997)”

Like me, you’ve probably wondered how daylight on Pluto compares to that on Earth. From 3 billion miles away, the Sun’s too small to see as a disk with the naked eye but still wildly bright. With NASA’s Pluto Time, select your city on an interactive map and get the time of day when the two are equal. For my city, daylight on Pluto equals the gentle light of early evening twilight six minutes after sunset. An ideal time for walking, but step lightly. In Pluto’s gentle gravity, you only weigh 1/15 as much as on Earth.

Pluto and its cohorts in the icy-asteroid-rich Kuiper Belt beyond the orbit of Neptune. Credit: NASA — Pluto and its inclined orbit are highlighted among the hundreds of thousands of icy asteroids in the Kuiper Belt beyond Neptune. Credit: NASA

New Horizons is the first mission to the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune. This region also is known as the “third” zone of our solar system, beyond the inner rocky planets and outer gas giants. Pluto is its most famous member, though not necessarily the largest. Eris, first observed in 2003, is nearly identical in size. It’s estimated there are hundreds of thousands of icy asteroids larger than 61 miles (100 km) across along with a trillion comets in the Belt, which begins at 30 a.u. (30 times Earth’s distance from the Sun) and reaches to 55 a.u.

During its fleeting flyby, New Horizons will slice across the Pluto system, turning this way and that to photograph and gather data on everything it can. Crucial occultations are shown that will be used to determine the structure and composition of Pluto’s (and possibly Charon’s) atmosphere. Credit: NASA with additions by the author — During its fleeting flyby, New Horizons will slice across the Pluto system, turning this way and that to photograph and gather data on everything it can. Crucial occultations are shown that will be used to determine the structure and composition of Pluto’s (and possibly Charon’s) atmosphere. Sunlight reflected from Charon will also faintly illuminate Pluto’s backside. Credit: NASA with additions by the author

Below you’ll find a schedule of events in Eastern Time. (Subtract one hour for Central, 2 hours for Mountain and 3 hours for Pacific). Keep in mind the probe will be busy shooting photos and gathering data during the flyby, so we’ll have to wait until Wednesday July 15 to see the the detailed close ups of Pluto and its moons. Even then, New Horizons’ recorders will be so jammed with data and images, it’ll take months to beam it all back to Earth.

Fasten your seat belts — we’re in for an exciting ride.

We’ll be reporting on results and sharing photos from the flyby here at Universe Today, but you’ll also want to check out NASA’s live coverage on NASA TV, its website and social media.

Monday, July 13
10:30 a.m. to noon – Media briefing on mission status and what to expect broadcast live on NASA TV

Tuesday, July 14
7:30 to 8 a.m. – Arrival at Pluto! Countdown program on NASA TV

At approximately 7:49 a.m., New Horizons is scheduled to be as close as the spacecraft will get to Pluto, approximately 7,800 miles (12,500 km) above the surface, after a journey of more than 9 years and 3 billion miles. For much of the day, New Horizons will be out of communication with mission control as it gathers data about Pluto and its moons.

The moment of closest approach will be marked during a live NASA TV broadcast that includes a countdown and discussion of what’s expected next as New Horizons makes its way past Pluto and potentially dangerous debris.

8 to 9 a.m. – Media briefing, image release on NASA TV

Wednesday, July 15

3 to 4 p.m. – Media Briefing: Seeing Pluto in a New Light; live on NASA TV and release of close-up images of Pluto’s surface and moons, along with initial science team reactions.

We’ll have the latest Pluto photos for you, but you can also check these excellent sites:

* Long Range Reconnaissance Imager (LORRI) archive
* Pluto Photojournal
* New Horizons science photo gallery

Need more Pluto? Spend a few minutes watching this excellent New York Times mission documentary.

July 10, 2015December 23, 2015 by Bob King

Scientists Captivated By Pluto’s Emerging Geological Wonders

Tantalizing signs of geology on Pluto are revealed in this image from New Horizons taken on July 9, 2015 from 3.3 million miles (5.4 million km) away. This annotated version shows the large dark feature nicknamed "the whale" that straddles Pluto's equator, a swirly band and a curious polygonal outline. At lower is a reference globe showing Pluto’s orientation in the image, with the equator and central meridian in bold. Credit: NASA-JHUAPL-SWRI

Bit by the Pluto bug? Day by day, new images appear showing an ever clearer view of a world we inexplicably love. Call it a dwarf planet. Call it a planet. It’s the unknown, and we can’t help but be drawn there.

Pluto made history when it was discovered in 1930. In 2015, it’s doing it all over again. Check out the new geology peeping into view.I’m reminded of the early explorers who shoved off in wooden ships in search of land across the water. After a long and often perilous journey, the mists would finally clear and the dark outline of land take form in the distance. It’s been 9 1/2 years since our collective Pluto voyage began. Yeah, we’re almost there.

Science team members react to the latest image of Pluto at the Johns Hopkins University Applied Physics Lab on July 10, 2015. Left to right: Cathy Olkin, Jason Cook, Alan Stern, Will Grundy, Casey Lisse, and Carly Howett. Credit: Michael Soluri — Science team members react to the latest image of Pluto at the Johns Hopkins University Applied Physics Lab on July 10, 2015. Left to right: Cathy Olkin, Jason Cook, Alan Stern, Will Grundy, Casey Lisse, and Carly Howett.
Credit: Michael Soluri

Today’s image release clearly shows a world growing more geologically diverse by the day.

“We’re close enough now that we’re just starting to see Pluto’s geology,” said New Horizons program scientist Curt Niebur, on NASA’s website. Niebur, who’s keenly interested in the gray area just above the whale’s “tail” feature, called it a “unique transition region with a lot of dynamic processes interacting, which makes it of particular scientific interest.”

The non-annotated version of the top photo. The 'whale' lies near the dwarf planet's equator. Pluto's axis is tilted 123° to its orbital plane. Credit: NASA — The non-annotated version of the top photo. The ‘whale’ lies near the dwarf planet’s equator. Pluto’s axis is tilted 123° to its orbital plane. Credit: NASA-JHUAPL-SWRI

Not only that, but the new photo shows an approximately 1,000-mile-long band of swirly terrain crossing the planet from east to northeast, a large, polygonal (roughly hexagonal) feature and new textures within the ‘whale’.

Neptune's largest moon Triton photographed on August 25, 1989 by Voyager 2. Credit: NASA — Neptune’s largest moon Triton photographed on August 25, 1989 by Voyager 2. Triton has a surface of mostly frozen nitrogen, a water ice-rich crust, an icy mantle and rock-metal core. Credit: NASA

Even to a layperson’s eye, Pluto’s terrain appears very different from that of Ceres or Vesta. In trying to make sense of what we see, Neptune’s moon Triton may be our best Plutonian analog with its frosts, weird cantaloupe terrain and an assortment of dark patches, some produced by icy volcanism.

New Horizons was about 3.7 million miles (6 million kilometers) from Pluto and Charon when it snapped this portrait late on July 8, 2015. Credits: NASA-JHUAPL-SWRI — New Horizons was about 3.7 million miles (6 million kilometers) from Pluto and Charon when it snapped this portrait late on July 8, 2015.
Credits: NASA-JHUAPL-SWRI

Other recent photos include this pretty view of Charon and Triton snapped late on July 8. NASA describes them eloquently as “two icy worlds, spinning around their common center of gravity like a pair of figure skaters clasping hands.” Charon and all of Pluto’s known moons formed from debris released when another planet struck Pluto long ago. New Horizons principal investigator Alan Stern attributes its bland color to its composition — mostly water ice. Pluto in contrast has a mantle of water ice, but it’s coated with methane, nitrogen and carbon dioxide ices and possibly organic compounds, too.

Color photos of Pluto and Charon side by side. The arcs along Pluto's right limb are artifacts but not the white border along the bottom. Could it be frost? Credit: — Color photos of Pluto and Charon side by side. The arcs along Pluto’s right limb are artifacts but not the white border along the bottom. Could it be frost? Credit: NASA-JHUAPL-SWRI

Hold on tight – there’s LOTS more to come!

July 8, 2015December 23, 2015 by Ken Kremer

Pluto’s ‘Heart’ Revealed as New Horizons Probe Starts Flyby Campaign: 5 Days Out

Pluto’s “Heart” is seen in this new image from New Horizons’ Long Range Reconnaissance Imager (LORRI) received on July 8, 2015 after normal science operations resumed following the scary July 4 safe mode anomaly that briefing shut down all science operations. The LORRI image has been combined with lower-resolution color information from the Ralph instrument. Credits: NASA-JHUAPL-SWRI

The Huge Heart of Pluto
Pluto’s “Heart” is seen in this new image from New Horizons’ Long Range Reconnaissance Imager (LORRI) received on July 8, 2015 after normal science operations resumed following the scary July 4 safe mode anomaly that briefing shut down all science operations. It shows ‘the heart and the whale’ along Pluto’s equator. The LORRI image has been combined with lower-resolution color information from the Ralph instrument. Credits: NASA-JHUAPL-SWRI
Story updated[/caption]

Emotions are rising exponentially with the rousing revelation that Pluto has a huge ‘Heart’ as revealed in stunning new imagery received just today (July 8) from NASA’s New Horizons spacecraft – which has also officially started its intensive flyby campaign merely 5 days out from humanity’s history making first encounter with the last unexplored planet in our Solar System on Tuesday, July 14.

Notably, today’s image showing Pluto’s ‘heart-shaped’ surface feature proves that New Horizons is now fully back in business following the nail-biting July 4 weekend anomaly that unexpectedly sent the probe into a protective status known as ‘safe mode’ and simultaneously sent mission engineers and scientists scurrying to their computer screens to resolve the scary issues and recover the probe back to full operation – just in the nick of time.

The intriguing ‘heart’ is the brightest area on Pluto and “may be a region where relatively fresh deposits of frost—perhaps including frozen methane, nitrogen and/or carbon monoxide—form a bright coating,” say mission scientists.

While in ‘safe mode’ all science operations were temporarily halted for nearly three days as the spacecraft inexorably zooms towards mysterious Pluto and its quintet of moons for our first up close reconnaissance of the frigid world and the Kuiper Belt.

Read my earlier story from July 6 here detailing how the science team and NASA resolved the July 4 anomaly and restored New Horizons to normal operations with little time to spare for its one time only flyby of the other ‘Red Planet’.

The close encounter sequence last for 9 days and it will take 16 months to relay back the vast quantity of data to be collected.

The view of Pluto’s ‘Heart’ was taken by the Long Range Reconnaissance Imager (LORRI) when the spacecraft was just under 5 million miles (8 million kilometers) from Pluto, and is the first to be received back on Earth since the anxiety rush caused by the July 4 anomaly.

The heart covers nearly half of Pluto’s now well resolved disk.

Right beside the large heart-shaped bright area, which measures some 1,200 miles (2,000 kilometers) across, is another enigmatic and elongated equatorial surface on the left side informally dubbed ‘the whale.’

Mission scientists say ‘the whale’ is one of the darkest regions visible to New Horizons and it measures some 1,860 miles (3,000 kilometers) in diameter, making it about 50% wider that the ‘heart.’

Above ‘the whale and the heart’ lies Pluto’s polar region that images show is intermediate in brightness.

NASA also released another perspective view of ‘the whale and the heart’ as seen below.

‘The whale and the heart of Pluto.’ This map of Pluto, made from images taken by the LORRI instrument aboard New Horizons, shows a wide array of bright and dark markings of varying sizes and shapes. Perhaps most intriguing is the fact that all of the darkest material on the surface lies along Pluto’s equator. The color version was created from lower-resolution color data from the spacecraft’s Ralph instrument. Credits: NASA-JHUAPL-SWRI — ‘The whale and the heart of Pluto.’
This map of Pluto, made from images taken by the LORRI instrument aboard New Horizons, shows a wide array of bright and dark markings of varying sizes and shapes. Perhaps most intriguing is the fact that all of the darkest material on the surface lies along Pluto’s equator. The color version was created from lower-resolution color data from the spacecraft’s Ralph instrument. Credits: NASA-JHUAPL-SWRI

Be sure to keep this entire area in mind – as if your appetites haven’t been whetted enough already – because “this view is centered roughly on the area that will be seen close-up during New Horizons’ July 14 closest approach,” says NASA.

“The next time we see this part of Pluto at closest approach, a portion of this region will be imaged at about 500 times better resolution than we see today,” said Jeff Moore, Geology, Geophysics and Imaging Team Leader of NASA’s Ames Research Center, in a statement. “It will be incredible!”

With barely 5 days to go until the once-in-a-lifetime opportunity for a fast flyby encounter of the ever intriguing binary planet traveling at the far flung reaches of the solar system, last minute glitches are the last thing anyone needs.

Why? Because there are no second chances as New Horizons barrels towards the Pluto system at approximately 30,000 miles per hour (over 48,000 kilometers per hour), which forms a binary planet with its largest known moon – Charon.

“The New Horizons spacecraft and science payload are now operating flawlessly,” Alan Stern, New Horizons principal investigator, Southwest Research Institute, Boulder, Colorado, announced at the July 6 post anomaly media briefing.

The nature of Pluto’s features that may appear to resemble craters or volcanoes is not yet known.

“We should be very cautious in interpreting these features,” Stern told Universe Today.

Latest color image of Pluto taken on July 3, 2015. Best yet image of Pluto was taken by the LORRI imager on NASA’s New Horizons spacecraft on July 3, 2015 at a distance of 7.8 million mi (12.5 million km), just prior to the July 4 anomaly that sent New Horizons into safe mode. Color data taken from the Ralph instrument gathered earlier in the mission. Credit: NASA/JHUAPL/SWRI

TThe probe was launched back on Jan. 19, 2006 on a United Launch Alliance Atlas V rocket on a 9 year voyage of over 3.6 billion miles (5.7 billion km).

“We are on our way to Pluto!” exclaimed Jim Green, director of Planetary Science, NASA Headquarters, Washington, at the July 6 news media briefing. “It’s really a historic time, fraught with many decisions and challenges on the way to the July 14 Pluto system encounter.”

“With Pluto in our sights, we’re going for the gold.”

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

This trio of images are the most recent high-resolution views of Pluto sent by NASA’s New Horizons spacecraft, including one showing the four mysterious dark spots on Pluto that have captured the imagination of the world. The Long Range Reconnaissance Imager (LORRI) obtained these three images between July 1 and 3 of 2015, prior to the July 4 anomaly that sent New Horizons into safe mode. Credit: NASA/JHUAPL/SWRI

July 6, 2015December 23, 2015 by Ken Kremer

New Horizons Exits Safe Mode, Operating Flawlessly for Upcoming Pluto Encounter

Latest color image of Pluto taken on July 3, 2015 shows 4 mysterious dark spots.
Best yet image of Pluto was taken by the LORRI imager on NASA’s New Horizons spacecraft on July 3, 2015 at a distance of 7.8 million mi (12.5 million km), just prior to the July 4 anomaly that sent New Horizons into safe mode. Color data taken from the Ralph instrument gathered earlier in the mission. Credit: NASA/JHUAPL/SWRI
Story updated[/caption]

Despite some hair-raising and unplanned 4th of July fireworks of sorts in deep space which caused NASA’s Pluto bound New Horizons spacecraft to enter “safe mode” due to a computer glitch and temporarily halt all science operations over the weekend, the spacecraft is now fully back on track, “healthy” and working “flawlessly” and set to resume all planned research investigations on Tuesday, July 7, NASA and top mission managers announced at a media briefing held this afternoon, Monday, July 6.

It’s now just exactly one week before the once-in-a-lifetime opportunity for a fast flyby encounter of the ever intriguing binary planet, at the far flung reaches of the solar system. And the great news could not come soon enough given the proximity of the flyby.

“The spacecraft is in excellent health and back in operation. New Horizons is barreling towards the Pluto system,” stated Jim Green, director of Planetary Science, NASA Headquarters, Washington, at the start of today’s news media briefing.

The $700 million mission remains on track to conduct the complex close flyby science sequence in its entirety, as planned over the next week, including the July 14 flyby of Pluto, despite the scary safe mode episode.

NASA unexpectedly lost contact with the New Horizons spacecraft on Saturday, July 4, at about 1:30 p.m. EDT after it suffered a memory related software anomaly and executed a protective operation known as “safe mode.” An anomaly investigation team was formed immediately.

“It’s really a historic time, but also fraught with many decisions and challenges on the way to the July 14 Pluto system encounter,” Green said.

The mission team quickly worked to reestablish contact with the piano shaped spacecraft about 90 minutes after the signal was lost.

“On Saturday we lost contact with the spacecraft. The New Horizons team immediately went into action. Within 90 minutes the signal was reacquired by the team, with the spacecraft in safe mode. They soon found the root cause and corrective actions were immediately taken to get the spacecraft back in business.”

The team worked tirelessly and diligently day and night over the holiday weekend to recover New Horizons back to full operation quickly and in time for the flyby encounter of Pluto on July 14, set for approximately 7:49 a.m. EDT (11:49 UTC) on July 14, said Glen Fountain, New Horizons project manager, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.

There are no second chances.

The software glitch occurred a day after new operating software was uploaded to New Horizons last Friday.

The spacecraft was trying to do two things at once on Saturday, compressing science data and writing command sequences while using up too much flash memory, explained Fountain.

“The computer was trying to do these two things at the same time, and the two were more than the processor could handle,” Fountain said.

“So the processor said ‘I’m overloaded.’ Then the spacecraft did exactly what it was supposed to do. It then switched to the backup computer and went into safe mode. At that point, we lost the downlink from the primary computer. We realized quickly what happened and put a recovery plan in place and recovered.”

Artist view of New Horizons passing Pluto and three of its moons. The ship is about the size of a grand piano and kept warm in the cold of the outer Solar System by heat release from the radioactive decay of plutonium within the probe's RTGs (Radioisotope Thermoelectric Generator). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — Artist view of New Horizons passing Pluto and three of its moons. The ship is about the size of a grand piano and kept warm in the cold of the outer Solar System by heat release from the radioactive decay of plutonium within the probe’s RTGs (Radioisotope Thermoelectric Generator). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

At this moment New Horizons is about 3 billion miles (4.9 billion km) from Earth and less than 6 million miles (9 million km) away from unmasking the secrets of tantalizing Pluto, Charon, its largest moon with which it forms a double planet system, and its four tiny and recently discovered moons. Charon is half the size of Pluto.

The round trip time for signals traveling at the speed of light is 8.5 hours. So it’s a very long time before commands from Earth can reach the spacecraft and for the team to determine their outcome. So the probe has to be able to operate on its own without direction from Earth during the intense and brief flyby period.

Pluto is the most distant and last unexplored planet in our Solar System, and therefore presents enormous complexities to those bold enough to dare the mightiest things.

“We expect a nominal flyby of Pluto from every indication now,” said Alan Stern, New Horizons principal investigator, Southwest Research Institute, Boulder, Colorado, announced at the media briefing.

“This object is unlike any other that we have observed,” Stern said. “Both Pluto and Charon are already surprising us.”

Less than 1 percent of the planned data was lost in the three days that the science instruments were shut off.

“It’s more important to focus on the later science during the flyby,” Stern elaborated.

“There is zero impact to the primary Group 1 highest-priority science objectives. And a minor impact to Group 2 and Group 3 objectives,” Stern elaborated.

“This is a speed bump in terms of the total return that we expect from this flyby.”

“I’m pleased that our mission team quickly identified the problem and assured the health of the spacecraft,” noted Green. “Now, with Pluto in our sights, we’re on the verge of returning to normal operations and going for the gold.”

New Horizons trajectory map to Pluto. Credit: NASA/JHUAPL/SWRI

The team said this type of software update will not be repeated and a similar type safe mode event should not recur.

Fountain said that during the encounter period, the probe can switch itself to exit safe mode event within about 7 minutes, depending on the situation, and minimize any science data losses.

New Horizons will swoop to within about 12,500 kilometers (nearly 7,800 miles) of Pluto’s surface.

It will zoom past Pluto at speeds of some 30,000 miles per hour (more than 48,000 kilometers per hour).

Today the team also released the best yet images of Pluto that were taken by the Long Range Reconnaissance Imager (LORRI). The trio of images were between July 1 and 3 of 2015, prior to the July 4 anomaly that sent New Horizons into safe mode.

The images show varying and enigmatic surface features on the different hemispheres of Pluto.

They also show the four mysterious dark spots on Pluto that have captured the imagination of the scientists and the world.

Their nature remains unknown at this time.

The probe was launched back in 2006 on a United Launch Alliance Atlas V rocket.

“We are on our way to Pluto!” Green exclaimed.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Animation of Pluto rotating from photos taken by New Horizons two weeks before the flyby. Credit:

July 6, 2015December 21, 2015 by Matt Williams

Newest Planet: Is it Pluto, Eris or Extrasolar?

With astronomers discovering new planets and other celestial objects all the time, you may be wondering what the newest planet to be discovered is. Well, that depends on your frame of reference. If we are talking about our Solar System, then the answer used to be Pluto, which was discovered by the American astronomer Clyde William Tombaugh in 1930.

Unfortunately, Pluto lost its status as a planet in 2006 when it was reclassified as a dwarf planet. Since then, another contender has emerged for the title of “newest planet in the Solar System” – a celestial body that goes by the name of Eris – while beyond our Solar System, thousands of new planets are being discovered.

But then, the newest planet might be the most recently discovered extrasolar planet. And these are being discovered all the time.

Continue reading “Newest Planet: Is it Pluto, Eris or Extrasolar?”

July 5, 2015December 23, 2015 by Bob King

NASA Loses Contact with New Horizons; Probe Now in Safe Mode

NASA briefly lost touch with the New Horizons spacecraft yesterday. Communications have been reestablished but science data will be delayed. Credit: NASA

For a nail-biting hour and 20 minutes, NASA lost contact yesterday afternoon July 4 with the New Horizons spacecraft just 9 days before its encounter with Pluto. Communication has since been reestablished and the spacecraft is healthy.

(UPDATE July 6: Great news! The mission will return to normal science operations July 7 – more details below.)

At 1:54 p.m. EDT, communications suddenly stopped and weren’t reestablished until 3:15 p.m. through NASA’s Deep Space Network. During the time it was out of contact with mission control, the spacecraft’s autonomous autopilot recognized the problem and did what it was programmed to do, switching from the main to the backup computer, according to NASA officials. The autopilot then commanded the backup computer to put New Horizons in “safe mode” — where all non-essential functions are shut down — and reinitiate communications with Earth.

Success! We’re now back in touch with the spacecraft and engineers are monitoring telemetry to figure out what went wrong. New Horizons is presently almost 3 billion miles (4.9 billion km) from Earth. Due to the 8.8 hour, round trip communication delay, full recovery is expected to take from one to several days. During that time New Horizons will be unable to collect science data.

If there’s any upside to this, it’s that it happened now instead of 9 days from now. On July 14 at 7:49:57 a.m. EDT the spacecraft will pass closest to Pluto.

Check back for updates. In the meantime, you can watch a live connection between New Horizons and the Deep Space Network. The probe is labeled NHPC and the dish 63 (first entry).

UPDATE: July 6. NASA announced earlier this morning that has concluded the glitch that caused the New Horizons spacecraft to go into safe mode was not due to a software or hardware fault.

“The underlying cause of the incident was a hard-to-detect timing flaw in the spacecraft command sequence that occurred during an operation to prepare for the close flyby. No similar operations are planned for the remainder of the Pluto encounter,” according to a NASA release.

No primary science will be lost and secondary goals were only slightly compromised. Mission control expects science operations to resume on July 7 and to conduct the entire close flyby sequence as planned.

“In terms of science, it won’t change an A-plus even into an A,” said New Horizons Principal Investigator Alan Stern.

Whew! What a sense of relief. Onward!

July 4, 2015December 23, 2015 by Bob King

Red-faced Pluto Full of Surprises

New Horizons scientists combined the latest black and white map of Pluto’s surface features (left) with a map of the planet’s colors (right) to produce a detailed color portrait of the planet’s northern hemisphere (center). Credits: NASA/JHUAPL/SWRI

Hey, Mars, you’ve got company. Looks like there’s a second “red planet” in the Solar System — Pluto. Color images returned from NASA’s New Horizons spacecraft, now just 10 days from its encounter with the dwarf planet, show a distinctly ruddy surface with patchy markings that strongly resemble Mars’ appearance in a small telescope.

On Mars, iron oxide or rust colors the planet’s soil, while Pluto’s coloration is likely caused by hydrocarbon molecules called tholins that are formed when cosmic rays and solar ultraviolet light interact with methane in Pluto’s atmosphere and on its surface. Airborne tholins fall out of the atmosphere and coat the surface with a reddish gunk.

Scientists at Johns Hopkins University’s Hörst Laboratory have produced complex chemical compounds called tholins, which may give Pluto its reddish hue. Credits: Chao He, Xinting Yu, Sydney Riemer, and Sarah Hörst, Johns Hopkins University — Scientists at Johns Hopkins University’s Hörst Laboratory have produced complex chemical compounds called tholins, which may give Pluto its reddish hue.
Credits: Chao He, Xinting Yu, Sydney Riemer, and Sarah Hörst, Johns Hopkins University

A particular color or wavelength of UV light called Lyman-alpha is most effective at stimulating the chemical reactions that build hydrocarbons at Pluto. Recent measurements with New Horizons’ Alice instrument reveal the diffuse glow of Lyman-alpha light all around the dwarf planet coming from all directions of space, not just the Sun.

Since one of the main sources of Lyman-alpha light besides the Sun are regions of vigorous star formation in young galaxies, Pluto’s cosmetic rouge may originate in events happening millions of light years away.

Triton's pink too! Montage of Neptune's largest moon, Triton (1,683 miles in diameter) and the planet Neptune showing the moon's sublimating south polar cap (bottom) and enigmatic "cantaloupe terrain". Credit: NASA — Triton’s pink too! Montage of Neptune’s largest moon, Triton (1,683 miles in diameter) and the planet Neptune showing the moon’s sublimating south polar cap (bottom) and enigmatic “cantaloupe terrain”. Photo taken by Voyager 2 in 1989. Credit: NASA

“Pluto’s reddish color has been known for decades, but New Horizons is now allowing us to correlate the color of different places on the surface with their geology and soon, with their compositions,” said New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado.

Tholins have been found on other bodies in the outer Solar System, including Titan and Triton, the largest moons of Saturn and Neptune, respectively, and made in laboratory experiments that simulate the atmospheres of those bodies.

True color photos showing the two hemispheres of Pluto. At right, you can clearly see the four streaks in a row. New Horizons will approach fly by the hemisphere on the left side. — True color photos showing the two hemispheres of Pluto photographed on June 27, 2015. At left, a large, dark red patch is visible. The four streaks in a row are seen at right. New Horizons will fly by the hemisphere in the left image. Credit: NASA/JHUAPL/SWRI

As you study the photos and animation, you’ll notice that Pluto’s largest dark spot is redder than the most of the surface; you also can’ help but wonder what’s going on with those four evenly-spaced dark streaks in the equatorial zone. When I first saw them, my reaction was “no way!” They look so neatly lined up I assumed it was an image artifact, but after seeing the rotating movie, maybe not. It’s more likely that low resolution enhances the appearance of alignment.

Dark streaks on Triton formed by deposits from ice or cryovolcanos. Credit: NASA — Dark streaks on Triton deposited downwind from ice or cryovolcanos. Credit: NASA

But what are they? Located as they are on the Charon-facing side of Pluto, they may be related to long-ago tidal stresses induced by each body on the other as they slowly settled into their current tidally-locked embrace or something as current as seasonal change.

Voyager 2 photographed cyrovolcanos at Triton during its 1989 flyby of the Neptune system. Nitrogen geysers and plumes of gas and ice as high as 5 miles (8 km) were seen erupting from active volcanoes, leaving dark streaks on its icy surface.

Images showing the increase in detail from late June through July 1 as New Horizons homes in on Pluto. Credit: — Images showing the increase in detail from late June through July 1 as New Horizons homes in on Pluto. That possible big crater (seen in bottom middle photo) now looks more like a large, dark patch, BUT we still don’t know for sure what it is. Credit: NASA / JHUAPL / SwRI / Björn Jónsson

It's instructive to compare these images based on observations with the Hubble Space Telescope made well before New Horizons's arrival. They appear to record the large dark spot and possible the multiple streaks. Credit: NASA/ESA — It’s instructive to compare these images, based on observations with the Hubble Space Telescope made well before New Horizons’s arrival, with current photos. They appear to record the large dark spot and possibly the multiple streaks. Credit: NASA/ESA

Seasonal heating from the Sun is the most likely cause for Triton’s eruptions; Pluto’s dark streaks may have a similar origin.

Animation of Pluto and Charon from images taken between June 23 and June 29. Credit: NASA/JHUAPL/SWR

To give you a better picture in your head how big these small bodies are, Pluto and Charon would both fit within the United States with room to spare. Credit: Laboratory for Atmospheric and Space Physics (LASP) — To better picture in your head how big these small bodies really are, Pluto and Charon would both fit within the United States with room to spare. Credit: Laboratory for Atmospheric and Space Physics (LASP)

Today, New Horizons lies just 7.4 million miles (11.9 million km) from its target. Sharpness and detail visible will rapidly improve in just a few days.

“Even at this resolution, Pluto looks like no other world in our Solar System,” said mission scientist Marc Buie of the Southwest Research Institute, Boulder in a recent press release.

Indeed!

June 30, 2015December 23, 2015 by Bob King

Is That a Big Crater on Pluto? Pyramidal Mountain Found on Ceres

Pluto with its enigmatic "crater" photographed on June 27. The apparent row of three depressions near the bottom of the globe are most likely artifacts from processing. Credit:

You’re probably as eager as I am for new images of Pluto and Ceres as both New Horizons and Dawn push ever closer to their respective little worlds. Recent photos, of which there are only a few, reveal some wild new features including what appears to a large crater on Pluto.

The latest photo of Pluto (lower left) and its largest moon Charon taken on June 29. A large possible crater-like feature is visible at lower right. Charon shows intriguing dark markings. Pluto's diameter is 1,471 miles (700 miles smaller than Earth's Moon); Charon is 750 miles across. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — The latest photo of Pluto (lower left) and its largest moon Charon taken on June 29. A large possible crater-like feature is visible at lower right. Charon shows intriguing dark markings. Pluto’s diameter is 1,471 miles (700 miles smaller than Earth’s Moon); Charon is 750 miles across. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

In the end, this apparent large impact might only be a contrast effect or worse, an artifact of over-processing, but there’s no denying its strong resemblance to foreshortened, shadow-filled craters seen on the Moon and other moons. It’s also encouraging that an earlier photo from June 27 shows the same feature. But the “crater” is just so … big! Its size seems disproportionate to the Pluto’s globe and recalls Saturn’s 246-mile-wide moon Mimas with its 81-mile-wide crater Herschel.

Pluto (right) and Charon, with its unusual dark north polar cap or “anti-cap” in a photo taken by New Horizons’ long-range camera on June 19, 2015. Pluto’s 1,471 miles in diameter; Charon’s half that size. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — Pluto (right) and Charon, showing an unusual dark north polar cap or “anti-cap” in a photo taken by New Horizons’ long-range camera on June 19, 2015. The two were about 20 million miles away at the time. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Astronomers speculate the impact that gouged out Herschel came perilously close to shattering the moon to pieces. If it does turn out to be an crater, Pluto’s surface opposite the impact will likely show many fractures. Not to be outdone, the dwarf planet’s largest moon, Charon, is starting to show a personality of its own with a prominent dark north polar cap.

Since polar caps are normally bright, icy features, some have referred to this one as an “anti-polar cap”. Speaking of ice, the bright rim around Pluto in the photo above may be nitrogen frost condensing out of Pluto’s scant atmosphere as it slowly recedes from the Sun. Think how cold it must have to get for nitrogen to freeze out. How about -346° F (-210° C)! For new images of the Pluto system, be sure to check the New Horizons LORRI gallery page.

Dawn took this photo of an intriguing pyramidal mountain on Ceres on June 14 from an altitude of 2,700 miles. It rises 3 miles above a relatively smooth surface. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA — Dawn took this photo of an intriguing pyramidal mountain (top center) on Ceres on June 14 from an altitude of 2,700 miles. It rises 3 miles above a relatively smooth surface. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Closer to home, new photos of Ceres show a peculiar, pyramid-shaped mountain towering 3 miles (5 km) high from a relatively smooth region between two large craters. Mountains poking from crater floors aren’t unusual. They’re tossed up after the crust later rebounds after a large impact. What makes this one unusual is the lack of an associated crater. Moreover, the mountain’s pale hue could indicate it’s younger than the surrounding landscape. As far as we can tell, it’s the only tall mountain on the face of the dwarf planet.

Another more overhead view of the mountain (right of center) taken by NASA's Dawn probe on June 6. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA — Another more overhead view of the mountain (right of center) taken by NASA’s Dawn probe on June 6. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Cropped version of the photo above. Notice the striations on the mountainside possibly from landslides. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The Dawn team also photographed that cluster of white spots again, this time with a very shot exposure in to eke out more details. What do you think? If you’re as interested in asteroids as I am, Italian astrophysicist Gianluca Masi, a frequent photo contributor to Universe Today, will host a special live Asteroid Day event today starting at 6 p.m. CDT (23:00 UT). Masi will review near-Earth asteroids, explain discovery techniques and observe several in real time.

The Dawn team greatly underexposed Ceres in order to tease out more details from the white spot cluster in this image made on June 15 from 2,700 miles altitude. I've lightened the limb of Ceres, so you can see the context better. Credit: — The Dawn team greatly underexposed Ceres in order to tease out more details from the white spot cluster in this image made on June 15 from 2,700 miles altitude. I’ve lightened the limb of Ceres to provide context. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn photographed the large crater at left along with an interesting chain of craters and possible fault or collapse features. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — Dawn photographed the large crater at left along with an interesting chain of craters and possible fault or collapse structures. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

June 25, 2015October 17, 2016 by David Dickinson

A Brief History of Nukes in Space

In just a few short weeks, NASA’s New Horizons spacecraft will make its historic flyby of Pluto and its moons. Solar panels are unable to operate in the dim nether regions of the outer solar system, and instead, New Horizons employs something that every spacecraft that has thus far ventured beyond Jupiter has carried in its tool kit: a plutonium-powered Radioisotope Thermoelectric Generator, or RTG.

The use of nuclear power to explore space is one of the few happy chapters of the post atomic age, and nuclear power may one day give us access to the stars.

In the 1950s, atomic energy was seen as a panacea as well as a curse, a sort of Sword of Damocles that both hung over the human race, while also holding the promise of its salvation. This was before the disasters in Fukushima Daiichi, Chernobyl and Three Mile Island, which would serve to sour the public to all things nuclear.

But early space pioneers also recognized the potential for nuclear energy in space exploration. One of the more bizarre proposals of the early Space Age was a plan named Project A119 which called for the United States to detonate a nuclear weapon on the Moon in full view of the Soviet Union as a show of power. Another interesting proposal dubbed Project Orion called for the construction of an interstellar spacecraft that would be propelled by atomic bombs detonated to its aft. And the very first human artifact shot into space may well have been a one ton steel plate that was accidentally propelled at high speed skyward during the Pascal B nuclear test in the Operation Plumbbob series on August 27^th, 1957. And the United States did indeed detonate nuclear weapons in space before the advent of the Limited Test Ban Treaty of 1967 that later forbade such tests. One amazing (and, as a child of the Cold War, very eerie to watch) such test known as Starfish Prime was carried out over the South Pacific in 1962:

One of the first spacecraft that sported an RTG was the Transit-4A satellite launched on June 29^th, 1961. Another similar satellite in the series, Transit-5BN-3, was lost shortly after launch along with its plutonium-fueled RTG, which reentered over the Indian Ocean. The Soviet satellite Kosmos 954 also reentered over the Canadian high Arctic in early 1978 along with its onboard nuclear reactor.

And when Apollo 13 returned to Earth, the crew jettisoned the Aquarius lunar landing module over the Pacific, where it reentered along with its plutonium RTG meant for the ALSEP experiments that the Apollo astronauts placed on the Moon during every mission.

Every launch from Cape Canaveral of a nuclear RTG is sure to draw a scattering of protesters, though NASA estimated a catastrophic launch failure involving an RTG rupture during the New Horizons launch at 1-in-360. These fears reached a crescendo during the launch of Cassini in 1997, which also featured an Earth slingshot flyby on August 18^th, 1999 en route to Saturn.

A nuclear RTG works by utilizing the waste heat generated by the radioactive decay of plutonium-238. This not only has a half-life of 87.7 years, but it also generates a very respectable 560 watt-seconds per kilogram per second. Unfortunately, the stuff we weaponize for nuclear bombs is a separate isotope known as Pu-239, and it can’t be repurposed for RTG use. The production of plutonium-239 for nuclear weapons during the Cold War did, however, also assure that the capability to also create Pu-238 for spaceflight was on hand until production was ended in the United States in 1989.

A roll call of RTG-equipped spacecraft reads like a ‘Who’s Who’ of outer solar system space exploration and includes: Pioneer 10 and 11, Galileo, Cassini, the Mars Science Laboratory, Voyagers 1 and 2, Vikings 1 and 2, and the aforementioned New Horizons spacecraft bound for Pluto.

Fun Fact: the plutonium powering Curiosity as it explores Mars was actually bought by NASA from the Russians.

As of this writing, the Mars Rover 2020 mission is the next spacecraft to break the surly bonds that will sport, like Curiosity, a plutonium-powered MMRTG. A proposed Uranus Orbiter mission named HORUS (This stands for—deep breath— the Herschel Orbiter for Reconnaissance of the Uranus System, because ‘Uranus Probe’ just doesn’t sound right) would have also utilized and RTG. The Europa Clipper mission to Jupiter’s moon Europa set to launch around 2025 chose solar cells over a nuclear RTG, though it’ll have to thread through the perilous radiation environment surrounding Jupiter. In fact, the Juno spacecraft set to enter orbit around the planet Jupiter next year will be the first Jovian mission that won’t utilize nuclear power, though it requires three enormous solar panels to compensate.

Just how much plutonium NASA has on hand courtesy of the Department of Energy is classified for security reasons, but it’s thought to have enough for one large and one scout-class mission remaining. New Horizons incorporates 10.9 kilograms of plutonium, and it’s interesting to note that any alien civilization that finds a human spacecraft orbiting the plane of our Milky Way galaxy millions of years hence could date its manufacture from the radioactive decay of what very little Pu-238 versus decay isotopes remains in its RTG.

NASA has announced that the US Department of Energy will indeed resume the production of plutonium to the tune of about 1.5 to 2 kilograms a year starting in 2016. On the downside, NASA did, however, halt the development of its Advanced Stirling Radioisotope Generator (ASRG) in 2013. This is a somewhat contradictory decision, fueled more by politics than practicality given the current scarcity of plutonium. The ASRG design was to be four times more efficient than current MMRTGs (MM stands for Multi-Mission) and would have thus utilized less of the dwindling stockpile of existing Pu-238.

Sadly, the lingering shortage of plutonium may have a dire impact on the future of outer solar system space exploration. As Cassini, New Horizons and the Voyager spacecraft wrap up their respective missions, our ‘eyes on the outer solar system’ may go dark, as the current golden era of planetary exploration draws to a close for now, or at least, awaits a new generation of plutonium-powered spacecraft to take up the mantle.