This new mosaic of Pluto is from the latest high-resolution images sent to Earth from the New Horizons spacecraft shows what you would see if you were approximately 1,100 miles (1,800 kilometers) above Pluto’s equatorial area, looking northeast over the dark, cratered, informally named Cthulhu Regio toward the bright, smooth, expanse of icy plains informally called Sputnik Planum. The entire expanse of terrain seen in this image is 1,100 miles (1,800 kilometers) across. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons scientists say they are “reeling” from the new images sent back from the spacecraft which were released today. The new data set shows an amazing range of complex features on Pluto’s surface and in its atmosphere.
New images show there might even be a field of dark wind-blown dunes, among other possibilities.
“Seeing dunes on Pluto — if that is what they are — would be completely wild, because Pluto’s atmosphere today is so thin,” said William B. McKinnon, a GGI deputy lead from Washington University, St. Louis. “Either Pluto had a thicker atmosphere in the past, or some process we haven’t figured out is at work. It’s a head-scratcher.”
Plus, a new view of Pluto’s hazy backlit atmosphere shows what are likely crepuscular rays — shadows cast on the haze by topography such as mountain ranges on Pluto, similar to the rays sometimes seen in the sky after the sun sets behind mountains on Earth.
Two different versions of an image of Pluto’s haze layers, taken by New Horizons as it looked back at Pluto’s dark side nearly 16 hours after close approach, from a distance of 480,000 miles (770,000 kilometers). The left version has had only minor processing, while the right version has been specially processed to reveal a large number of discrete haze layers in the atmosphere. Subtle parallel streaks in the haze may be crepuscular rays- shadows cast on the haze by topography such as mountain ranges on Pluto, similar to the rays sometimes seen in the sky after the sun sets behind mountains on Earth.Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Scientists say these new images reveal that Pluto’s global atmospheric haze has many more layers than scientists realized, and that the haze actually creates a twilight effect that softly illuminates nightside terrain near sunset, making them visible to the cameras aboard New Horizons.
“This bonus twilight view is a wonderful gift that Pluto has handed to us,” said John Spencer, a GGI deputy lead from SwRI. “Now we can study geology in terrain that we never expected to see.”
This image of Pluto from NASA’s New Horizons spacecraft, processed in two different ways, shows how Pluto’s bright, high-altitude atmospheric haze produces a twilight that softly illuminates the surface before sunrise and after sunset, allowing the sensitive cameras on New Horizons to see details in nighttime regions that would otherwise be invisible. The right-hand version of the image has been greatly brightened to bring out faint details of rugged haze-lit topography beyond Pluto’s terminator, which is the line separating day and night. The image was taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
These new images are the first to be sent from the spacecraft since shortly after it flew past the Pluto system in July of this year. This is the beginning of an “intensive” downlink session that will last for a year or more, sending back the 50 gigabits or so of data the spacecraft collected and stored on its digital recorders during the flyby. These new images are “selected high priority” data-sets that the science team has been anxiously waiting for.
The new images are “lossless” — meaning the data sent back from the New Horizon spacecraft is using a type of data compression algorithms that allows the original data to be perfectly reconstructed from the compressed data. Planetary astronomer Alex Parker said on Twitter that this means the even views we’ve seen in the previous Pluto images from New Horizons are much sharper and crisper.
Here are more:
A close-up of a dark area on the edge of the heart-shaped light region on Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Besides the dunes and new atmospheric imagery, other views show nitrogen ice flows that apparently oozed out of mountainous regions onto plains, and even networks of valleys that may have been carved by material flowing over Pluto’s surface. They also show large regions that display chaotically jumbled mountains, which reminded many of the terrain on Jupiter’s icy moon Europa.
“The surface of Pluto is every bit as complex as that of Mars,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging (GGI) team at NASA’s Ames Research Center. “The randomly jumbled mountains might be huge blocks of hard water ice floating within a vast, denser, softer deposit of frozen nitrogen within the region informally named Sputnik Planum.”
In the center of this 300-mile (470-kilometer) wide image of Pluto from NASA’s New Horizons spacecraft is a large region of jumbled, broken terrain on the northwestern edge of the vast, icy plain informally called Sputnik Planum, to the right. The smallest visible features are 0.5 miles (0.8 kilometers) in size. This image was taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
This image of Pluto’s largest moon Charon, taken by NASA’s New Horizons spacecraft 10 hours before its closest approach to Pluto on July 14, 2015 from a distance of 290,000 miles (470,000 kilometers), is a recently downlinked, much higher quality version of a Charon image released on July 15. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
The New Horizons spacecraft is now about 5 billion kilometers (more than 3 billion miles) from Earth, and more than 69 million kilometers (43 million miles) beyond Pluto. The team says the spacecraft is healthy and all systems are operating normally.
You can see all the latest imagery sent back from New Horizons at this website. New images will be added every week, according to the New Horizons staff, likely on Fridays.
Details of Pluto’s largest moon, Charon, are revealed in this image from New Horizons’ Long Range Reconnaissance Imager (LORRI), taken July 13, 2015, from a distance of 289,000 miles (466,000 kilometers), combined with color information obtained by New Horizons’ Ralph instrument on the same day. The distinctive red marking in Charon’s north polar region is currently being studied by scientists. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
As we await new imagery and data from the New Horizons’ flyby of the Pluto system to be transmitted to Earth, one piece of the Pluto-Charon puzzle that scientists are looking forward learning more about is the mysterious “dark pole” on Charon. Images sent immediately after the flyby reveal Charon’s north polar region is much darker than the lighter-colored material surrounding it, and it actually has a reddish cast to it.
The New Horizons team says the red pole appears to be a thin deposit of dark material over a distinct, sharply bounded, angular feature – perhaps and impact basin – and scientists hope to learn more by studying higher-resolution images that are currently being beamed back to Earth from the spacecraft.
Carly Howett, a senior research scientist at the Southwest Research Institute, is one of the scientists studying the mystery of what is causing this color difference and why it shows up at Charon’s north pole.
“Looking at Charon, it’s very clear that the northern polar region is much redder than the rest of the moon,” said Howett in a post on the New Horizons website. “Surfaces vary in color when something about them changes.”
So what is this red material? The leading theory right now is that material from Pluto’s atmosphere is falling to Charon and being ensnared in the polar region by what is known as “cold-trapping.”
It’s is so cold at Charon’s poles – temperatures there vary are just a tad warmer than absolute zero, between -433 and -351 °F (-258 and -213 °C) – that any gases settling there would freeze solid instead of escaping. And with the combination of extremely cold temperatures and solar radiation, the material is transformed to a new substance, and is being trapped on the pole. Howett said it likely won’t disappear with any seasonal changes on Charon.
“We know Pluto’s atmosphere is mainly nitrogen, with some methane and carbon monoxide,” she said, “so we expect that these same constituents are slowly coating Charon’s winter pole. The frozen ices would sublimate away again as soon as Charon’s winter pole emerges back into sunlight, except for one important detail: solar radiation modifies these ices to produce a new substance, which has a higher sublimation temperature and can’t sublimate and then escape from Charon.”
What is the new substance? Scientists can’t say for sure yet, but it might be a tholin.
Scientists at Johns Hopkins University’s Hörst Laboratory have produced complex chemical compounds called tholins, which may give Pluto its reddish hue. (Image credit: Chao He, Xinting Yu, Sydney Riemer, and Sarah Hörst, Johns Hopkins University).
What is a tholin? Tholins were first created in a laboratory by in the 1970s by Carl Sagan and his team at Cornell. According to planetary scientist Sarah Hörst, who wrote about tholins on The Planetary Society website, Sagan and his team would take mixtures of cosmically relevant gases and irradiate them with various energy sources. The result was “a brown, sometimes sticky, residue,” as Sagan described them in a paper he wrote in 1979.
Hörst said Sagan and team “were searching for answers to questions ranging from ‘why is the Great Red Spot red’ to ‘how did life on Earth originate’ and in the process produced material for which there was no name.”
They came up with the name “tholin,” and theorized that tholins could be a constituent of the Earth’s primitive oceans and therefore as relevant to the origin of life.
In the article Hörst wrote, “I have been studying tholin for almost a decade and in my experience the most frequently used synonyms for tholin are “gunk”, “brown gunk”, and “complex organic gunk”. Tholin is also often described as a “tar-like” substance. Words like tar, kerogen, bitumen, petroleum, asphalt, etc. all describe substances that are potentially similar to tholin in some ways. However, these materials all result from life; they are’biotic.’”
Charon approach from New Horizons. Credit: NASA/Damian Peach
Finding out more about what is going on at Charon’s north pole is indeed intriguing. Tholins might be the same material that give Pluto its reddish-brown hue in some regions, too.
Howett told Universe Today that the main instrument on New Horizons that will really pin down the compositional information is LEISA (Linear Etalon Imaging Spectral Array).
“This instrument observes 250 wavelengths between 1.25-2.5 microns, making it ideal for detecting the spectral signature of solid features,” she said via email. “We don’t know exactly the composition of the tholin on Charon (many different types are possible) but with LEISA we can look for differences in the spectra between the Charon’s anomalous red region and those surrounding it – to give us some hints of the change in surface composition and the “raw ingredients” for the tholin.”
For example, Howett said, maybe they’ll see more hydrogen cyanide (HCN) around the north pole region, which would open up a lot of complex chemistry options.
“We will start getting this data down in the next few weeks, so hopefully we’ll have some answers soon!” she said.
Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame. Credits: NASA/JHUAPL/SwRI
If you thought the New Horizons spacecraft flyby of the Pluto system happened waaaay too fast and you’re pining for more images and data, you are in luck. What the spacecraft has been able to send back so far is just the tip of the icy dwarf planet, so to speak.
Starting tomorrow, Saturday, September 5, 2015, the spacecraft will begin an “intensive” downlink session that will last for a year or more, sending back the tens of gigabits of data the spacecraft collected and stored on its digital recorders during the flyby. What will come first are “selected high priority” data-sets that the science team has been anxiously waiting for.
“This is what we came for – these images, spectra and other data types that are going to help us understand the origin and the evolution of the Pluto system for the first time,” said New Horizons Principal Investigator Alan Stern. “And what’s coming is not just the remaining 95 percent of the data that’s still aboard the spacecraft – it’s the best datasets, the highest-resolution images and spectra, the most important atmospheric datasets, and more. It’s a treasure trove.”
Plus, every Friday from here on out, you can count on getting new, unprocessed pictures from the Long Range Reconnaissance Imager (LORRI) on the New Horizons project website. Here’s where you can find the images, and the next LORRI set is scheduled for posting on Sept. 11, so set your calendars.
It’s been 7 weeks since New Horions’ historic flyby of the Pluto system, and during this quick pass, the spacecraft was designed “to gather as much information as it could, as quickly as it could, as it sped past Pluto and its family of moons – then store its wealth of data to its digital recorders for later transmission to Earth,” said the mission team.
A portrait from the final approach. Pluto and Charon display striking color and brightness contrast in this composite image from July 11, showing high-resolution black-and-white LORRI images colorized with Ralph data collected from the last rotation of Pluto. Color data being returned by the spacecraft now will update these images, bringing color contrast into sharper focus. Credits: NASA-JHUAPL-SWRI
Why is it taking so long? The spacecraft runs on between 2-10 watts of power, and it had to prioritize on data collection during the flyby. The data has been stored on two onboard, solid-state, 8 gigabyte memory banks. The spacecraft’s main processor compresses, reformats, sorts and stored the data on a recorder, similar to a flash memory card for a digital camera.
One issue is the time it takes to get data from New Horizons as it speeds even farther away from Earth, past the Pluto system. Even moving at light speed, the radio signals from New Horizons containing data need more than 4 ½ hours to cover the 4 billion km (3 billion miles) to reach Earth.
But the biggest issue is the relatively low “downlink” rate at which data can be transmitted to Earth, especially when you compare it to rates now common for high-speed Internet surfers.
All communications with New Horizons – from sending commands to the spacecraft, to downlinking all of the science data from the historic Pluto encounter – happen through NASA’s Deep Space Network of antenna stations in (clockwise, from top left) Madrid, Spain; Goldstone, California, U.S.; and Canberra, Australia. Even traveling at the speed of light, radio signals from New Horizons need more than 4 ½ hours to travel the 3 billion miles between the spacecraft and Earth. Credit: NASA.
During the Jupiter flyby in February 2007, New Horizons data return rate was about 38 kilobits per second (kbps), which is slightly slower than the transmission speed for most computer modems. Now, after the flyby, the average downlink rate is going to be approximately 1-4 kilobits per second, depending on how the data is sent and which Deep Space Network antenna is receiving it. Sometimes, when possible, the spacecraft will be able to increase the rate by downlinking with both of its transmitters through NASA’s largest antennas of the DSN. But even then, it will take until late 2016 to send Pluto flyby data stored on the spacecraft’s recorders.
Patience you must have, my young padawan.
“The New Horizons mission has required patience for many years, but from the small amount of data we saw around the Pluto flyby, we know the results to come will be well worth the wait,” said Hal Weaver, New Horizons project scientist.
The data received by the DSN (you can watch the live data link happen on the Eyes of the Solar System DSN NOW page) will be sent to the New Horizons Mission Operations Center at the Applied Physics Lab a Johns Hopkins University, where data will be “unpacked” and stored. Then mission operations and instrument teams will scour the engineering data for performance trend information, while science data will be copied to the Science Operations Center at the Southwest Research Institute in Boulder, Colorado.
At the Science Ops Center, data will pass through “pipeline” software that converts the data from instrumental units to scientific units, based on calibration data obtained for each instrument. Both the raw and calibrated data files will be formatted for New Horizons science team members to analyze. Both the raw and calibrated data, along with various ancillary files (such as documents describing the pipeline process or the science instruments) will be archived at the Small Bodies Node of NASA’s Planetary Data System.
We’ve only had blurry images of Pluto up until New Horizons. So what did we learn when we got up close and personal with Pluto and its moons?
Clyde Tombaugh first discovered Pluto in 1930. He saw only see a single speck of light moving slowly in front of the background stars as he flipped photographic plates back and forth. Sadly, this was the best anyone could do for decades. Even the mighty Hubble, the most sensitive instrument ever focused on Pluto, could only resolve a few grainy pixels.
It’s because Pluto is really really far away: 7.5 billion kilometers. Just the light alone from there takes over 4 hours to reach us. In order to get any more information, humanity needed to reach out and send a spacecraft to Pluto, and photograph it, up close and personal.
In 1989, Alan Stern and a group of planetary scientists began working on a mission. Their work culminated in NASA’s New Horizons spacecraft, launched in 2006, beginning a 9 and a half year journey. And unless you’ve been living in a lunar lava tube, you know that New Horizons finally reached its destination in mid July 2015, passing a narrow 12,472 kilometers above the surface.
For the very first time in human history, we saw a member of the Kuiper Belt right up in it’s business. And now I retire these old low quality images Pluto! Begone artist’s illustrations!
From here on out, we’re all about sick high def photos of the surface and its moons. I for one am going to revel in them for a while.
So fashion shoots aside, what did we actually learn about Pluto? The primary mission was to map the geography of Pluto and its biggest moon, Charon. It would study the surface chemistry of these icy worlds, and measure their atmospheres, if they even exist at all.
The mission had a few other objectives, and of course, planetary scientists knew that the spacecraft would just surprise us with stuff we never expected. Kuiper Belt objects like Pluto and Charon are ancient; geologists expected them to be pockmarked with craters, large and small.
Views of Pluto during New Horizons’ approach. Credit: NASA/Damian Peach
Surprisingly, New Horizons showed relatively smooth surfaces on both worlds. Pluto has a Texas-sized region newly named Sputnik Planum, where exotic ices flow like glaciers. Frozen nitrogen, carbon dioxide and methane ices act just like the ones we have here on Earth. We can see from the relative lack of craters that this process is still happening.
Pluto has mountains. Mountains! Close ups show a young range with peaks as high as 11,000 feet, or 3,500 meters. Here’s the crazy part. Those exotic chemicals that act like snow and ice? They’re not hard enough to make mountain peaks like this.
At extreme cold temperatures, water ice becomes as hard as rock. These mountains are made of ice, and they’re very young, probably less than 100 million years old. There could be plate tectonics on Pluto, but with ice, not rock. My mind is blown.
Pluto’s moon Charon has a huge chasm longer and deeper than the Grand Canyon in Arizona and although scientists hoped to see an atmosphere, the reality was beyond anyone’s expectations.
Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame. Credits: NASA/JHUAPL/SwRI
New Horizons detected a thin nitrogen atmosphere at Pluto. It could be snowing nitrogen on Pluto right now. There could be faint winds, since there are regions on Pluto that look like they might have undergone weathering.
Take a look at this photograph as New Horizons zipped away. You can see the atmosphere clearly surrounding the dwarf planet, interacting with the solar wind and creating a tail that stretches away from the Sun.
Here’s my favorite thing we learned. Pluto is about 80 km larger than previous estimates, which makes it the largest Kuiper Belt Object found so far. Even bigger than Eris, which is still a little more massive. So maybe it’s time to revisit that Pluto planethood debate again. I’m just messing with you. No good will ever come from having that debate. It will only end in tears.
Interestingly, the data connection between Earth and New Horizons is tenuous. Possibly the worst internet since AOL. It can only transmit back about 1kb of data per second, which means that we’ll need to wait about 16 months for the photographs and data to be sent home during the first few days of the flyby.
As an extra bonus, this isn’t the last we’re going to hear from New Horizons. Because it’s so far away, as the spacecraft can only trickle data back to Earth. It’s going to take almost 2 years for all the images and measurements it gathered during its flyby to get back to Earth for scientists to study. Expect many more discoveries and announcements over the coming years, and more videos from us.
Now that Pluto has finally been explored, where do you think we should go next in the Solar System? Tell us in the comments below.
On July 14, 2015, after nine and a half years journeying across the Solar System, NASA’s New Horizons spacecraft made its historic close pass of Pluto and its moon Charon. Traveling a relative velocity of nearly 13.8 km/s (that’s almost 31,000 mph!) New Horizons passed through the Pluto system in a matter of hours but the views it captured from approach to departure held the world spellbound with their unexpected beauty. Those images and data – along with a bit of imagination – have been used by space imaging enthusiast Björn Jónsson to create an animation of New Horizons’ Pluto pass as if we were traveling along with the spacecraft – check it out above.
You can find more science images and discoveries about Pluto and Charon from New Horizons here, and see more renderings and animations by Jónsson on his website here.
The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA
For thousands of years, astronomers have watched comets travel close to Earth and light up the night sky. In time, these observations led to a number of paradoxes. For instance, where were these comets all coming from? And if their surface material vaporizes as they approach the Sun (thus forming their famous halos), they must formed farther away, where they would have existed there for most of their lifespans.
In time, these observations led to the theory that far beyond the Sun and planets, there exists a large cloud of icy material and rock where most of these comets come from. This existence of this cloud, which is known as the Oort Cloud (after its principal theoretical founder), remains unproven. But from the many short and long-period comets that are believed to have come from there, astronomers have learned a great deal about it structure and composition.
Definition:
The Oort Cloud is a theoretical spherical cloud of predominantly icy planetesimals that is believed to surround the Sun at a distance of up to around 100,000 AU (2 ly). This places it in interstellar space, beyond the Sun’s Heliosphere where it defines the cosmological boundary between the Solar System and the region of the Sun’s gravitational dominance.
Like the Kuiper Belt and the Scattered Disc, the Oort Cloud is a reservoir of trans-Neptunian objects, though it is over a thousands times more distant from our Sun as these other two. The idea of a cloud of icy infinitesimals was first proposed in 1932 by Estonian astronomer Ernst Öpik, who postulated that long-period comets originated in an orbiting cloud at the outermost edge of the Solar System.
In 1950, the concept was resurrected by Jan Oort, who independently hypothesized its existence to explain the behavior of long-term comets. Although it has not yet been proven through direct observation, the existence of the Oort Cloud is widely accepted in the scientific community.
Structure and Composition:
The Oort Cloud is thought to extend from between 2,000 and 5,000 AU (0.03 and 0.08 ly) to as far as 50,000 AU (0.79 ly) from the Sun, though some estimates place the outer edge as far as 100,000 and 200,000 AU (1.58 and 3.16 ly). The Cloud is thought to be comprised of two regions – a spherical outer Oort Cloud of 20,000 – 50,000 AU (0.32 – 0.79 ly), and disc-shaped inner Oort (or Hills) Cloud of 2,000 – 20,000 AU (0.03 – 0.32 ly).
The outer Oort cloud may have trillions of objects larger than 1 km (0.62 mi), and billions that measure 20 kilometers (12 mi) in diameter. Its total mass is not known, but – assuming that Halley’s Comet is a typical representation of outer Oort Cloud objects – it has the combined mass of roughly 3×1025 kilograms (6.6×1025 pounds), or five Earths.
Based on the analyses of past comets, the vast majority of Oort Cloud objects are composed of icy volatiles – such as water, methane, ethane, carbon monoxide, hydrogen cyanide, and ammonia. The appearance of asteroids thought to be originating from the Oort Cloud has also prompted theoretical research that suggests that the population consists of 1-2% asteroids.
Earlier estimates placed its mass up to 380 Earth masses, but improved knowledge of the size distribution of long-period comets has led to lower estimates. The mass of the inner Oort Cloud, meanwhile, has yet to be characterized. The contents of both Kuiper Belt and the Oort Cloud are known as Trans-Neptunian Objects (TNOs), because the objects of both regions have orbits that that are further from the Sun than Neptune’s orbit.
A belt of comets called the Oort Cloud is theorized to encircle the Solar system (image credit: NASA/JPL).
Origin:
The Oort cloud is thought to be a remnant of the original protoplanetary disc that formed around the Sun approximately 4.6 billion years ago. The most widely accepted hypothesis is that the Oort cloud’s objects initially coalesced much closer to the Sun as part of the same process that formed the planets and minor planets, but that gravitational interaction with young gas giants such as Jupiter ejected them into extremely long elliptic or parabolic orbits.
Recent research by NASA suggests that a large number of Oort cloud objects are the product of an exchange of materials between the Sun and its sibling stars as they formed and drifted apart. It is also suggested that many – possibly the majority – of Oort cloud objects were not formed in close proximity to the Sun.
Alessandro Morbidelli of the Observatoire de la Cote d’Azur has conducted simulations on the evolution of the Oort cloud from the beginnings of the Solar System to the present. These simulations indicate that gravitational interaction with nearby stars and galactic tides modified cometary orbits to make them more circular. This is offered as an explanation for why the outer Oort Cloud is nearly spherical in shape while the Hills cloud, which is bound more strongly to the Sun, has not acquired a spherical shape.
A comparison of the Solar System and its Oort Cloud. 70,000 years ago, Scholz’s Star and companion passed along the outer boundaries of our Solar System. Credit: NASA, Michael Osadciw/University of Rochester
Recent studies have shown that the formation of the Oort cloud is broadly compatible with the hypothesis that the Solar System formed as part of an embedded cluster of 200–400 stars. These early stars likely played a role in the cloud’s formation, since the number of close stellar passages within the cluster was much higher than today, leading to far more frequent perturbations.
Comets:
Comets are thought to have two points of origin within the Solar System. They start as infinitesimals in the Oort Cloud and then become comets when passing stars knock some of them out of their orbits, sending into a long-term orbit that take them into the inner solar system and out again.
Short-period comets have orbits that last up to two hundred years while the orbits of long-period comets can last for thousands of years. Whereas short-period comets are believed to have emerged from either the Kuiper Belt or the scattered disc, the accepted hypothesis is that long-period comets originate in the Oort Cloud. However, there are some exceptions to this rule.
For example, there are two main varieties of short-period comet: Jupiter-family comets and Halley-family comets. Halley-family comets, named for their prototype (Halley’s Comet) are unusual in that although they are short in period, they are believed to have originated from the Oort cloud. Based on their orbits, it is suggested they were once long-period comets that were captured by the gravity of a gas giant and sent into the inner Solar System.
Evolution of a comet as it orbits the sun. Credit: Laboratory for Atmospheric and Space Sciences/ NASA
Exploration:
Because the Oort Cloud is so much farther out than the Kuiper Belt, the region remained unexplored and largely undocumented. Space probes have yet to reach the area of the Oort cloud, and Voyager 1 – the fastest and farthest of the interplanetary space probes currently exiting the Solar System – is not likely to provide any information on it.
At its current speed, Voyager 1 will reach the Oort cloud in about 300 years, and will will take about 30,000 years to pass through it. However, by around 2025, the probe’s radioisotope thermoelectric generators will no longer supply enough power to operate any of its scientific instruments. The other four probes currently escaping the Solar System –Voyager 2, Pioneer 10 and 11, and New Horizons – will also be non-functional when they reach the Oort cloud.
Exploring the Oort Cloud presents numerous difficulties, most of which arise from the fact that it is incredible distant from Earth. By the time a robotic probe could actually reach it and begin exploring the area in earnest, centuries will have passed here on Earth. Not only would those who had sent it out in the first place be long dead, but humanity will have most likely invented far more sophisticated probes or even manned craft in the meantime.
Still, studies can be (and are) conducted by examining the comets that it periodically spits out, and long-range observatories are likely to make some interesting discoveries from this region of space in the coming years. It’s a big cloud. Who knows what we might find lurking in there?
Global Color Mosaic of Triton, taken by Voyager 2 in 1989. Credit: NASA/JPL/USGS
The planets of the outer Solar System are known for being strange, as are their many moons. This is especially true of Triton, Neptune’s largest moon. In addition to being the seventh-largest moon in the Solar System, it is also the only major moon that has a retrograde orbit – i.e. it revolves in the direction opposite to the planet’s rotation. This suggests that Triton did not form in orbit around Neptune, but is a cosmic visitor that passed by one day and decided to stay.
And like most moons in the outer Solar System, Triton is believed to be composed of an icy surface and a rocky core. But unlike most Solar moons, Triton is one of the few that is known to be geologically active. This results in cryovolcanism, where geysers periodically break through the crust and turn the surface Triton into what is sure to be a psychedelic experience!
Discovery and Naming:
Triton was discovered by British astronomer William Lassell on October 10th, 1846, just 17 days after the discovery of Neptune by German astronomer Johann Gottfried Galle. After learning about the discovery, John Herschel – the son of famed English astronomer William Herschel, who discovered many of Saturn’s and Uranus’ moons – wrote to Lassell and recommended he observe Neptune to see if it had any moons as well.
New Horizons image of Neptune and its largest moon, Triton, taken by the LORRI instrument on June 23, 2010. Credit: NASA
Lassell did so and discovered Neptune’s largest moon eight days later. Thirty-four years later, French astronomer Camille Flammarion named the moon Triton – after the Greek sea god and son of Poseidon (the equivalent of the Roman god Neptune) – in his 1880 bookAstronomie Populaire. It would be several decades before the name caught on however. Until the discovery of the second moon Nereid in 1949, Triton was commonly known simply as “the satellite of Neptune”.
Size, Mass and Orbit:
At 2.14 × 1022 kg, and with a diameter of approx. 2,700 kilometers (1,680 miles) km, Triton is the largest moon in the Neptunian system – comprising more than 99.5% of all the mass known to orbit the planet. In addition to being the seventh-largest moon in the Solar System, it is also more massive than all known moons in the Solar System smaller than itself combined.
With no axial tilt and an eccentricity of virtually zero, the moon orbits Neptune at a distance of 354,760 km (220,438 miles). At this distance, Triton is the farthest satellite of Neptune, and orbits the planet every 5.87685 Earth days. Unlike other moons of its size, Triton has a retrograde orbit around its host planet.
Most of the outer irregular moons of Jupiter and Saturn have retrograde orbits, as do some of Uranus’s outer moons. However, these moons are all much more distant from their primaries, and are rather small in comparison. Triton also has a synchronous orbit with Neptune, which means it keeps one face aimed towards the planet at all times.
As Neptune orbits the Sun, Triton’s polar regions take turns facing the Sun, resulting in seasonal changes as one pole, then the other, moves into the sunlight. Such changes were observed in April of 2010 by astronomers using the European Southern Observatory’s Very Large Telescope.
Another all-important aspect of Triton’s orbit is that it is decaying. Scientists estimate that in approximately 3.6 billion years, it will pass below Neptune’s Roche limit and will be torn apart.
Composition:
Triton has a radius, density (2.061 g/cm3), temperature and chemical composition similar to thatof Pluto. Because of this, and the fact that it circles Neptune in a retrograde orbit, astronomers believe that the moon originated in the Kuiper Belt and later became trapped by Neptune’s gravity.
Another theory has it that Triton was once a dwarf planet with a companion. In this scenario, Neptune captured Triton and flung its companion away when the giant gas moved further out into the solar system, billions of years ago.
Also like Pluto, 55% of Triton’s surface is covered with frozen nitrogen, with water ice comprising 15–35% and dry ice (aka. frozen carbon dioxide) forming the remaining 10–20%. Trace amounts of methane and carbon monoxide ice are believed to exist there as well, as are small amounts of ammonia (in the form of ammonia dihydrate in the lithosphere).
Triton’s density suggests that its interior is differentiated between a solid core made of rocky material and metals, a mantle composed of ice, and a crust. There is enough rock in Triton’s interior for radioactive decay to power convection in the mantle, which may even be sufficient to maintain a subterranean ocean. As with Jupiter’s moon of Europa, the proposed existence of this warm-water ocean could mean the presence of life beneath the icy crusts.
Atmosphere and Surface Features:
Triton has a considerably high albedo, reflecting 60–95% of the sunlight that reaches it. The surface is also quite young, which is an indication of the possible existence of an interior ocean and geological activity. The moon has a reddish tint, which is probably the result of the methane ice turning to carbon due to exposure to ultraviolet radiation.
Triton is considered to be one of the coldest places in the Solar System. The moon’s surface temperature is approx. -235°C while Pluto averages about -229°C. Scientists say that Pluto may drop as low as -240°C at the furthest point from the Sun in its orbit, but it also gets much warmer closer to the Sun, giving it a higher overall temperature average.
It is also one of the few moons in the Solar System that is geologically active, which means that its surface is relatively young due to resurfacing. This activity also results in cryovolcanism, where water ammonia and nitrogen gas burst forth from the surface instead of liquid rock. These nitrogen geysers can send plumes of liquid nitrogen 8 km above the surface of the moon.
Triton (lower left) compared to the Moon (upper left) and Earth (right), to scale. Credit: NASA/JPL/USGS
Because of the geological activity constantly renewing the moon’s surface, there are very few impact craters on Triton. Like Pluto, Triton has an atmosphere that is thought to have resulted from the evaporation of ices from its surface. Like its surface ices, Triton’s tenuous atmosphere is made up of nitrogen with trace amounts of carbon monoxide and small amounts of methane near the surface.
This atmosphere consists of a troposphere rising to an altitude of 8km, where it then gives way to a thermosphere that reaches out to 950 km from the surface. The temperature of Triton’s upper atmosphere, at 95-100 K (ca.-175 °C/-283 °F) is higher than that at the surface, due to the influence of solar radiation and Neptune’s magnetosphere.
A haze permeates most of Triton’s troposphere, thought to be composed largely of hydrocarbons and nitriles created by the action of sunlight on methane. Triton’s atmosphere also has clouds of condensed nitrogen that lie between 1 and 3 km from the surface.
Observations taken from Earth and by the Voyager 2 spacecraft have shown that Triton experiences a warm summer season every few hundred years. This could be the result of a periodic change in the planet’s albedo (i.e. its gets darker and redder) which could be caused by either frost patterns or geological activity.
Using the CRIRES instrument on ESO’s Very Large Telescope, a team of astronomers has been able to see that the summer is in full swing in Triton’s southern hemisphere. Credit: ESO
This change would allow more heat to be absorbed, followed by an increase in sublimation and atmospheric pressure. Data collected between 1987 and 1999 indicated that Triton was approaching one of these warm summers.
Exploration:
When NASA’s Voyager 2 made a flyby of Neptune in August of 1989, the mission controllers also decided to conduct a flyby of Triton – similar to Voyager 1‘s encounter with Saturn and Titan. When it made its flyby, most of the northern hemisphere was in darkness and unseen by Voyager.
Because of the speed of Voyager’s visit and the slow rotation of Triton, only one hemisphere was seen clearly at close distance. The rest of the surface was either in darkness or seen as blurry markings. Nevertheless, the Voyager 2 spacecraft managed to capture several images of the moon and spotted geysers of liquid nitrogen blasting out of two distinct features on the surface.
In August of 2014, in anticipation of New Horizons impending encounter with Pluto, NASA restored these photos and used them to create the first global color map of Triton. Produced by Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, the map was also used to make a movie (shown below) that recreated the historic Voyager 2 encounter in time for the 25th anniversary of the event.
Yes, Triton is indeed an unusual moon. Aside from its rather unique characteristics (retrograde motion, geological activity) the moon’s landscape is likely to be an amazing sight. For anyone standing on the surface, surrounded by colorful ices, plumes of nitrogen and ammonia, a nitrogen haze and Neptune’s big blue disc hanging on the sky, the experience would seem like something akin to a hallucination.
In the end, it is too bad that the Solar System will one day be saying good-bye to this moon. Because of the nature of its orbit, the moon will eventually fall into Neptune’s gravity well and break up. At which point, Neptune will have a huge ring like Saturn, until those particles crash into the planet as well.
That too would be something to behold. One can only hope that humanity will still be around in 3.6 billion years to witness it!
Hi Res mosaic of ‘Tombaugh Regio’ shows the heart-shaped region on Pluto and focuses on icy mountain ranges of ‘Norgay Montes’ and ice plains of ‘Sputnik Planum.’ The new mosaic combines highest resolution imagery captured by NASA’s New Horizons LORRI imager during history making closest approach flyby on July 14, 2015, draped over a wider, lower resolution view of Tombaugh Regio. Inset at left shows possible wind streaks. Inset at right shows global view of Pluto with location of huge heart-shaped region in context. Annotated with place names. Credit: NASA/JHUAPL/SWRI/ Marco Di Lorenzo/Ken Kremer/kenkremer.com
APPLIED PHYSICS LABORATORY, LAUREL, MD – The highest resolution images ever taken of Pluto by humanity’s first spacecraft ever to visit the last planet in our solar system revealed unanticipated new discoveries of ice mountains as tall as the Rockies and vast craterless plains spanning hundreds of miles (kilometers) across – are now shown in our newly created context mosaic (featured above and below) of the heart-shaped ‘Tombaugh Regio’ area that dominates the alien planet’s surface.
This first high resolution surface mosaic was created from a newly unveiled series of black and white images centered in the Heart of Pluto’s huge ‘Heart, including the ice mountains of ‘Sputnik Planum’ and icy plains of ‘Norgay Montes.’
They were captured by New Horizons’ high resolution Long Range Reconnaissance Imager (LORRI) on July 14 as the probe barreled past the Pluto-Charon binary planet system only four days ago on Tuesday, July 14, at over 31,000 mph (49,600 kph).
These highest resolution LORRI images focused on the “Heart of the Heart” of Pluto have now been stitched into a mosaic by the image processing team of Marco Di Lorenzo and Ken Kremer.
Pluto’s bright heart-shaped region has now been informally renamed “Tombaugh Regio,’ announced John Spencer, New Horizons science team co-investigator at the post flyby media briefing on July 15.
The mosaic of Pluto’s ‘Tombaugh Regio’ is based on the initial imagery released so far as of July 17.
This annotated view of a portion of Pluto’s Sputnik Planum (Sputnik Plain), named for Earth’s first artificial satellite, shows an array of enigmatic features. The surface appears to be divided into irregularly shaped segments that are ringed by narrow troughs, some of which contain darker materials. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as a half-mile (1 kilometer) across are visible. Credits: NASA/JHUAPL/SWRI
A pair of high resolution LORRI images was aimed at areas now informally named Norgay Montes (Norgay Mountains) and Sputnik Planum (Sputnik Plain).
Norgay Montes is informally named for Tenzing Norgay, one of the first two humans to reach the summit of Mount Everest, along with Sir Edmund Hillary. Sputnik Planum is informally named for Earth’s first artificial satellite launched by the Soviet Union in 1957.
The two LORRI images are draped over a wider, lower resolution view of Tombaugh Regio – in annotated and unannotated versions. This is highest resolution currently available.
To the left of the mosaic are two small inserts showing possible “wind streaks” say the researchers.
To the right of the mosaic is a global view of Pluto showing the location of Tombaugh Regio and also outlined to show the precise location of the high resolution LORRI mosaic.
Hi Res mosaic of ‘Tombaugh Regio’ shows the heart-shaped region on Pluto and focuses on icy mountain ranges of ‘Norgay Montes’ and ice plains of ‘Sputnik Planum.’ The new mosaic combines highest resolution imagery captured by NASA’s New Horizons LORRI imager during history making closest approach flyby on July 14, 2015. Inset at left shows possible wind streaks. Inset at right shows global view of Pluto with location of huge heart-shaped region in context. Credit: NASA/JHUAPL/SWRI/ Marco Di Lorenzo/Ken Kremer/kenkremer.com
The LORRI images were taken from a distance of 48,000 miles (77,000 kilometers) from the surface of the planet about 1.5 hours prior to the closest approach at 7:49 a.m. EDT on July 14. The images easily resolve structures smaller than a mile across.
The frozen region of Norgay Montes is situated north of Pluto’s icy mountain range at Sputnik Planum.
“This terrain is not easy to explain,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California.
“The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations.”
“The landscape is astoundingly amazing. There are a few ancient impact craters on Pluto. But other areas like “Tombaugh Regio” show no craters. The landform change processes are occurring into current geologic times.”
“There are no impact craters in a frozen area north of Pluto’s icy mountains we are now informally calling ‘Sputnik Planum’ after Earth’s first artificial satellite.”
New close-up images of a region near Pluto’s equator reveal a giant surprise — a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body. Credits: NASA/JHU APL/SwRI
‘Sputnik Planum’ is composed of a broken surface of irregularly-shaped segments. The polygonal shaped areas are roughly 12 miles (20 kilometers) across, bordered by what appear to be shallow troughs based on a quick look at the data.
The mountain ranges height rival those of the Rockies, says Moore.
The new LORRI close-ups show the icy mountain range has peaks jutting as high as 11,000 feet (3,500 meters) above the surface, announced John Spencer, New Horizons science team co-investigator at the media briefing.
“It’s a very young surface, probably formed less than 100 million years old,’ said Spencer. “It may be active now.”
New Horizons science team co-investigator John Spencer examines print of the newest Pluto image taken on July 13, 2015 after the successful Pluto flyby. Credit: Ken Kremer/kenkremer.com
“Judging from the absence of impact craters, it’s clear that Sputnik Planum couldn’t possibly be more than 100 million years old, and possibly is still being shaped to this day by geologic processes,” noted Moore. “This could be only a week old for all we know.”
During the fast flyby encounter, the New Horizons spacecraft pointed its suite of seven science instruments exclusively on all the bodies in the Pluto system, to maximize the capture of scientific data, as quickly as possible, and store it onto its two solid state digital recorders for later playback.
A major challenge for the mission is the rather slow “downlink” transmission of data back to Mission Control on Earth. Since the average “downlink” is only about 2 kilobits per second via its two transmitters, it will take about 16 months to send all the flyby data back to Earth.
Therefore the team has carefully selected just a few of the highest resolution images and other key instrument data for quick playback. The remaining flyby data will be prioritized for streaming.
“Over 50 gigabits of data were collected during the encounter and flyby periods,” New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado, said during the July 17 media briefing.
“So far less than 1 gigabit of data has been returned.”
New Horizons discovered that Pluto is the biggest object in the outer solar system and thus the ‘King of the Kuiper Belt’.
The Kuiper Belt comprises the third and outermost region of worlds in our solar system.
If the spacecraft remains healthy as expected, the science team plans to target New Horizons to fly by another smaller Kuiper Belt Object (KBO) as soon as 2018.
Pluto Explored at Last. The New Horizons mission team celebrates successful flyby of Pluto in the moments after closest approach at 7:49 a.m. EDT on July 14, 2015. New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO., left, Johns Hopkins University Applied Physics Laboratory (APL) Director Ralph Semmel, center, and New Horizons Co-Investigator Will Grundy Lowell Observatory hold an enlarged print of an U.S. stamp with their suggested update after Pluto became the final planet in our solar system to be explored by an American space probe (crossing out the words ‘not yet’) – at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.com
Watch for Ken’s continuing coverage of the Pluto flyby. He was onsite reporting live on the flyby and media briefings for Universe Today from the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
NASA Associate Administrator for the Science Mission Directorate John Grunsfeld, left, New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO, second from left, New Horizons Mission Operations Manager Alice Bowman of the Johns Hopkins University Applied Physics Laboratory (APL), second from right, and New Horizons Project Manager Glen Fountain of APL, right, are seen at the conclusion of a press conference after the team received confirmation from the spacecraft that it has completed the flyby of Pluto, Tuesday, July 14, 2015 at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.com
This annotated view of a portion of Pluto’s Sputnik Planum (Sputnik Plain), named for Earth’s first artificial satellite, shows an array of enigmatic features. The surface appears to be divided into irregularly shaped segments that are ringed by narrow troughs, some of which contain darker materials. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as a half-mile (1 kilometer) across are visible. Credits: NASA/JHUAPL/SWRI
This annotated view of a portion of Pluto’s Sputnik Planum (Sputnik Plain), named for Earth’s first artificial satellite, shows an array of enigmatic features. The surface appears to be divided into irregularly shaped segments that are ringed by narrow troughs, some of which contain darker materials. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as a half-mile (1 kilometer) across are visible. Credits: NASA/JHUAPL/SWRI
See 3 image mosaic below[/caption]
The jaw dropping new imagery of young plains of water ice was publicly released today, July 17, by NASA and scientists leading the New Horizons mission during a media briefing, and has already resulted in ground breaking new scientific discoveries at the last planet in our solar system to be visited by a spacecraft from Earth.
“We have now visited every planet in our solar system with American spacecraft,” said NASA Administrator Charles Bolden. “These findings are already causing us to rethink the dynamics of interior geologic processes.”
New data and dazzling imagery are now from streaming back some 3 billion miles across interplanetary space to mission control on Earth and researchers eagerly awaiting the fruits of more than two decades of hard labor to get to this once-in-a-lifetime opportunity.
“I can’t wait for the new discoveries!” exclaimed Bolden at today’s media briefing.
“Over 50 gigabits of data were collected during the encounter and flyby periods,” New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado, said during the media briefing.
“So far less than 1 gigabit of data has been returned.”
It will take some 16 months for all the Pluto flyby data to be transmitted back to Earth.
And the team has not been disappointed because the results so far shows Pluto to possess tremendously varied terrain that “far exceed our expectations.”
Video Caption: In the center left of Pluto’s vast heart-shaped feature – informally named “Tombaugh Regio” – lies a vast, craterless plain that appears to be no more than 100 million years old, and is possibly still being shaped by geologic processes. This frozen region is north of Pluto’s icy mountains and has been informally named Sputnik Planum (Sputnik Plain), after Earth’s first artificial satellite. Credits: NASA/JHUAPL/SWRI
Two new high resolution images captured by the probes Long Range Reconnaissance Imager (LORRI) on July 14 were released today and taken from a distance of 48,000 miles (77,000 kilometers). Features as small as one-half mile (1 kilometer) across are visible in the images – shown above and below.
They were snapped from frozen region lying north of Pluto’s icy mountains, in the center-left of the heart feature, informally named “Tombaugh Regio” (Tombaugh Region) after Clyde Tombaugh, who discovered Pluto in 1930.
“This terrain is not easy to explain,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California.
“The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations.”
“The landscape is astounding. There are a few ancient impact craters on Pluto. But other areas like “Tombaugh Regio” show no craters. The landform change processes are occurring into current geologic times.”
“There are no impact craters in a frozen area north of Pluto’s icy mountains we are now informally calling ‘Sputnik Planum’ after Earth’s first artificial satellite.”
‘Sputnik Planum’ is composed of a broken surface of irregularly-shaped segments. The polygonal shaped areas are roughly 12 miles (20 kilometers) across, bordered by what appear to be shallow troughs based on a quick look at the data.
Notably, some of the clumps are filled with mysterious darker material. Hills are also visible in some areas, which may have been pushed up. Etched areas on the surface may have been formed by sublimation process where the water ice turns directly from the solid to the gas phase due to the extremely negligible atmosphere pressure.
In some places there are also streaks that may have formed from windblown processes and pitted areas.
Three image mosaic of ‘Tombaugh Regio,’ Pluto’s heart-shaped region, combining highest resolution imagery captured by NASA’s New Horizons LORRI imager during closest approach flyby on July 14, 2015. Credits: NASA/JHUAPL/SWRI. Additional processing Ken Kremer/Marco Di Lorenzo
“It’s just pure coincidence that we got the highest resolution data at Sputnik Planum which is of the most interest scientifically,” Moore noted.
Moore indicated that the team is working on a pair of theories as to how these polygonal segments were formed.
“The irregular shapes may be the result of the contraction of surface materials, similar to what happens when mud dries. Alternatively, they may be a product of convection, similar to wax rising in a lava lamp. On Pluto, convection would occur within a surface layer of frozen carbon monoxide, methane and nitrogen, driven by the scant warmth of Pluto’s interior,” Moore explained.
Pluto’s polygons look remarkably similar to the Martian polygons upon which NASA’s Phoenix lander touched down on in 2008 and dug into. Perhaps they were formed by similar mechanisms or difference ones, contraction or convection, Moore told me during the briefing.
As of yesterday, New Horizons spacecraft completed and exited the Pluto encounter phase, said Stern. “We are now collecting departure science.”
New Horizons is already over 3 million miles beyond Pluto and heading to its next yet to be determined target in the Kuiper Belt.
“With the flyby in the rearview mirror, a decade-long journey to Pluto is over –but, the science payoff is only beginning,” said Jim Green, director of Planetary Science at NASA Headquarters in Washington.
“Data from New Horizons will continue to fuel discovery for years to come.”
Counting down to less than 3 minutes from New Horizons closest approach to Pluto, Jim Green, NASA Planetary Science Division Director, addresses the team, guests and media on Tuesday, July 14, 2015 at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.com
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Pluto Explored at Last
The New Horizons mission team celebrates successful flyby of Pluto in the moments after closest approach at 7:49 a.m. EDT on July 14, 2015. New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO., left, Johns Hopkins University Applied Physics Laboratory (APL) Director Ralph Semmel, center, and New Horizons Co-Investigator Will Grundy Lowell Observatory hold an enlarged print of an U.S. stamp with their suggested update after Pluto became the final planet in our solar system to be explored by an American space probe (crossing out the words ‘not yet’) – at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.comIn the center left of Pluto’s vast heart-shaped feature – informally named “Tombaugh Regio” – lies a vast, craterless plain that appears to be no more than 100 million years old, and is possibly still being shaped by geologic processes. This frozen region is north of Pluto’s icy mountains and has been informally named Sputnik Planum (Sputnik Plain), after Earth’s first artificial satellite. The surface appears to be divided into irregularly-shaped segments that are ringed by narrow troughs. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers). Features as small as one-half mile (1 kilometer) across are visible. Credits: NASA/JHUAPL/SWRI
Artist's impression of the New Horizons spacecraft in orbit around Pluto (Charon is seen in the background). Credit: NASA/JPL
Humans have been sending spacecraft to other planets, as well as asteroid and comets, for decades. But rarely have any of these ventured into the outer reaches of our Solar System. In fact, the last time a probe reached beyond the orbit of Saturn to explore the worlds of Neptune, Uranus, Pluto and beyond was with the Voyager 2 mission, which concluded back in 1989.
But with the New Horizons mission, humanity is once again peering into the outer Solar System and learning much about its planets, dwarf planets, planetoids, moons and assorted objects. And as of July 14th, 2015, it made its historic rendezvous with Pluto, a world that has continued to surprise and mystify astronomers since it was first discovered.
Background:
In 1980, after Voyager 1‘s flyby of Saturn, NASA scientists began to consider the possibility of using Saturn to slingshot the probe towards Pluto to conduct a flyby by 1986. This would not be the case, as NASA decided instead to conduct a flyby of Saturn’s moon of Titan – which they considered to be a more scientific objective – thus making a slingshot towards Pluto impossible.
Because no mission to Pluto was planned by any space agency at the time, it would be years before any missions to Pluto could be contemplated. However, after Voyager 2′s flyby of Neptune and Triton in 1989, scientists once again began contemplating a mission that would take a spacecraft to Pluto for the sake of studying the Kuiper Belt and Kuiper Belt Objects (KBOs).
Artist’s impression of the Voyager spacecraft in flight. Credit: NASA/JPL
In May 1989, a group of scientists, including Alan Stern and Fran Bagenal, formed an alliance called the “Pluto Underground”. Committed to the idea of mounting an exploratory mission to Pluto and the Kuiper Belt, this group began lobbying NASA and the US government to make it this plan a reality. Combined with pressure from the scientific community at large, NASA began looking into mission concepts by 1990.
During the course of the late 1990s, a number of Trans-Neptunian Objects (TNOs) were discovered, confirming the existence of the Kuiper Belt and spurring interest in a mission to the region. This led NASA to instruct the JPL to re-purpose the mission as a Pluto and KBO flyby. However, the mission was scrapped by 2000, owing to budget constraints.
Backlash over the cancellation led NASA’s Science Mission Directorate to create the New Frontiers program which began accepting mission proposals. Stamatios “Tom” Krimigis, head of the Applied Physics Laboratory’s (APL) space division, came together with Alan Stern to form the New Horizons team. Their proposal was selected from a number of submissions, and officially selected for funding by the New Frontiers program in Nov. 2001.
Despite additional squabbles over funding with the Bush administration, renewed pressure from the scientific community allowed the New Horizons team managed to secure their funding by the summer of 2002. With a commitment of $650 million for the next fourteen years, Stern’s team was finally able to start building the spacecraft and its instruments.
Engineers working on the New Horizons spacecraft’s Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. Credit: NASA
Mission Profile:
New Horizons was planned as a voyage to the only unexplored planet in the Solar System, and was originally slated for launch in January 2006 and arrival at Pluto in 2015. Alan Stern was selected as the mission’s principal investigator, and construction of the spacecraft was handled primarily by the Southwest Research Institute (SwRI) and the Johns Hopkins Applied Physics Laboratory, with various contractor facilities involved in the navigation of the spacecraft.
Meanwhile, the US Naval Observatory (USNO) Flagstaff Station – in conjunction with NASA and JPL – was responsible for performing navigational position data and related celestial frames. Coincidentally, the UNSO Flagstaff station was where the photographic plates that led to the discovery of Pluto’s moon Charon came from.
In addition to its compliment of scientific instruments (listed below), there are several cultural artifacts traveling aboard the spacecraft. These include a collection of 434,738 names stored on a compact disc, a piece of Scaled Composites’s SpaceShipOne, and a flag of the USA, along with other mementos. In addition, about 30 g (1 oz) of Clyde Tombaugh’s ashes are aboard the spacecraft, to commemorate his discovery of Pluto in 1930.
The New Horizons spacecraft takes off on Jan. 19, 2006 from the Kennedy Space Center for its planned close encounter with Pluto. Credit: NIKON/Scott Andrews/NASA
Instrumentation:
The New Horizons science payload consists of seven instruments. They are (in alphabetically order):
Alice: An ultraviolet imaging spectrometer responsible for analyzing composition and structure of Pluto’s atmosphere and looks for atmospheres around Charon and Kuiper Belt Objects (KBOs).
LORRI: (Long Range Reconnaissance Imager) a telescopic camera that obtains encounter data at long distances, maps Pluto’s farside and provides high resolution geologic data.
PEPSSI: (Pluto Energetic Particle Spectrometer Science Investigation) an energetic particle spectrometer which measures the composition and density of plasma (ions) escaping from Pluto’s atmosphere.
Ralph: A visible and infrared imager/spectrometer that provides color, composition and thermal maps.
REX: (Radio Science EXperiment) a device that measures atmospheric composition and temperature; passive radiometer.
SDC: (Student Dust Counter) built and operated by students, this instrument measures the space dust peppering New Horizons during its voyage across the solar system.
SWAP: (Solar Wind Around Pluto) a solar wind and plasma spectrometer that measures atmospheric “escape rate” and observes Pluto’s interaction with solar wind.
The instruments New Horizons will use to characterize Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Launch:
Due to a series of weather-related delays, the New Horizons mission launched on January 19th, 2006, two days later than originally scheduled. The spacecraft took off from Cape Canaveral Air Force Station, Florida, at 15:00 EST (19:00 UTC) atop an Atlas V 551 rocket. This was the first launch of this particular rocket configuration, which has a third stage added to increase the heliocentric (escape) speed.
The spacecraft left Earth faster than any spacecraft to date, achieving a launch velocity of 16.5 km/s. It took only nine hours to reach the Moon’s orbit, passing lunar orbit before midnight (EST) on the same day it was launched. It has not, however, broken Voyager 1‘s record – which is currently traveling at 17.145 km/s (61,720 km/h, 38,350 mph) relative to the Sun – for being the fastest spacecraft to leave the Solar System.
Inner Solar System:
Between January and March, 2006, mission controllers guided the probe through a series of trajectory-correction maneuvers (TCMs). During the week of February 20th, 2006, controllers conducted in-flight tests on three of the major on board science instruments. On April 7th, the spacecraft passed the orbit of Mars, moving at roughly 21 km/s (76,000 km/h; 47,000 mph) away from the Sun.
At this point in its journey, the spacecraft had reached a distance of 243 million kilometers from the Sun, and approximately 93.4 million km from Earth. On June 13th, 2006, the New Horizons spacecraft passed the tiny asteroid 132524 APL at a distance of 101,867 km (63,297 mi) when it was closest.
Using the Ralph instrument, New Horizons was able to capture images of the asteroid, estimating to be 2.5 km (1.6 mi) in diameter. The spacecraft also successfully tracked the asteroid from June 10th-12th, 2006, allowing the mission team to test the spacecraft’s ability to track rapidly moving objects.
First images of Pluto taken by New Horizons in September 2006. Credit: NASA
From September 21st-24th, New Horizons managed to capture its first images of Pluto while testing the LORRI instruments. These images, which were taken from a distance of approximately 4,200,000,000 km (2.6×109 mi) or 28.07 AU and released on November 28th, confirmed the spacecraft’s ability to track distant targets.
Outer Solar System:
On September 4th, 2006, New Horizons took its first pictures of Jupiter at a distance of 291 million kilometers (181 million miles). The following January, it conducted more detailed surveys of the system, capturing an infrared image of the moon Callisto, and several black and white images of Jupiter itself.
By February 28th, 2007, at 23:17 EST (03:17, UTC) New Horizons made its closest approach to Europa, at a distance of 2,964,860 km (1,842,278 mi). At 01:53:40 EST (05:43:40 UTC), the spacecraft made its flyby of Jupiter, at a distance of 2.3 million km (1.4 million mi) and received a gravity assist.
The Jupiter flyby increased New Horizons‘ speed by 4 km/s (14,000 km/h; 9,000 mph), accelerating the probe to a velocity of 23 km/s (83,000 km/h; 51,000 mph) relative to the Sun and shortening its voyage to Pluto by three years.
The encounter with Jupiter not only provided NASA with the opportunity to photograph the planet using the latest equipment, it also served as a dress rehearsal for the spacecraft’s encounter with Pluto. As well as testing the imaging instruments, it also allowed the mission team to test the communications link and the spacecraft’s memory buffer.
Black and white image of Jupiter viewed by LORRI in January 2007. Credit: NASA/John Hopkins University Applied Physics Laboratory/Southwest Research Institute
One of the main goals during the Jupiter encounter was observing its atmospheric conditions and analyzing the structure and composition of its clouds. Heat-induced lightning strikes in the polar regions and evidence of violent storm activity were both observed. In addition, the Little Red Spot, was imaged from up close for the first time. The New Horizons spacecraft also took detailed images of Jupiter’s faint ring system. Traveling through Jupiter’s magnetosphere, the spacecraft also managed to collect valuable particle readings.
The flyby of the Jovian systems also gave scientists the opportunity to examine the structure and motion of Io’s famous lava plumes. New Horizons measured the plumes coming from the Tvashtar volcano, which reached an altitude of up to 330 km from the surface, while infrared signatures confirmed the presence of 36 more volcanoes on the moon.
Callisto’s surface was also analyzed with LEISA, revealing how lighting and viewing conditions affect infrared spectrum readings of its surface water ice. Data gathered on minor moons such as Amalthea also allowed NASA scientists to refine their orbit solutions.
After passing Jupiter, New Horizons spent most of its journey towards Pluto in hibernation mode. During this time, New Horizons crossed the orbit of Saturn (June 8, 2008) and Uranus on (March 18, 2011). In June 2014, the spacecraft emerged from hibernation and the team began conducting instrument calibrations and a course correction,. By August 24th, 2014, it crossed Neptune’s orbit on its way to Pluto.
New Horizons Long Range Reconnaissance Imager (LORRI) captured these two images of Jupiter’s outermost large moon, Callisto, during its flyby in February 2007. Credit: NASA/JPL
Rendezvous with Pluto:
Distant-encounter operations at Pluto began on January 4th, 2015. Between January 25th to 31st, the approaching probe took several images of Pluto, which were released by NASA on February 12th. These photos, which were taken at a distance of more than 203,000,000 km (126,000,000 mi) showed Pluto and its largest moon, Charon.
Investigators compiled a series of images of the moons Nix and Hydra taken from January 27th through February 8th, 2015, beginning at a range of 201,000,000 km (125,000,000 mi), while Kerberos and Styx were captured by photos taken on April 25.
On July 4th, 2015, NASA lost contact with New Horizons after it experienced a software anomaly and went into safe mode. On the following day, NASA announced that they had determined it to be the result of a timing flaw in a command sequence. By July 6th, the glitch had been fixed and the probe had exited safe mode and began making its approach.
The New Horizons spacecraft made its closest approach to Pluto at 07:49:57 EDT (11:49:57 UTC) on July 14th, 2015, and then Charon at 08:03:50 EDT (12:03:50 UTC). Telemetries confirming a successful flyby and a healthy spacecraft reached Earth on 20:52:37 EDT (00:52:37 UTC).
During the flyby, the probe captured the clearest pictures of Pluto to date, and full analyses of the data obtained is expected to take years to process. The spacecraft is currently traveling at a speed of 14.52 km/s (9.02 mi/s) relative to the Sun and at 13.77 km/s (8.56 mi/s) relative to Pluto.
Full trajectory of New Horizons space probe (sideview). Credit: pluto.jhuapl.edu
Future Objectives:
With its flyby of Pluto now complete, the New Horizons probe is now on its way towards the Kuiper Belt. The goal here is to study one or two other Kuiper Belt Objects, provided suitable KBOs are close to New Horizons‘ flight path.
Three objects have since been selected as potential targets, which were provisionally designated PT1 (“potential target 1”), PT2 and PT3 by the New Horizons team. These have since been re-designated as 2014 MU69 (PT1), 2014 OS393 (PT2), and 2014 PN70 (PT3).
All of these objects have an estimated diameter of 30–55 km, are too small to be seen by ground telescopes, and are 43–44 AU from the Sun, which would put the encounters in the 2018–2019 period. All are members of the “cold” (low-inclination, low-eccentricity) classical Kuiper Belt, and thus very different from Pluto.
Even though it was launched far faster than any outward probe before it, New Horizons will never overtake either Voyager 1 or Voyager 2 as the most distant human-made object from Earth. But then again, it doesn’t need to, given that what it was sent out to study all lies closer to home.
What’s more, the probe has provided astronomers with extensive and updated data on many of planets and moons in our Solar System – not the least of which are the Jovian and Plutonian systems. And last, but certainly not least, New Horizons is the first spacecraft to have it made it out to such a distance since the Voyager program.
And so we say so long and good luck to New Horizons, not to mention thanks for providing us with the best images of Pluto anyone has ever seen! We can only hope she fares well as she makes its way into the Kuiper Belt and advances our knowledge of the outer Solar System even farther.
