Voyager Archives

August 15, 2013April 26, 2016 by Jason Major

Voyager 1: Is It In or Is It Out?

Has Voyager 1 actually left the Solar System? Some researchers are saying yes. (Image: NASA/JPL-Caltech)

Nearly 18.7 billion kilometers from Earth — about 17 light-hours away — NASA’s Voyager 1 spacecraft is just about on the verge of entering interstellar space, a wild and unexplored territory of high-energy cosmic particles into which no human-made object has ever ventured. Launched in September 1977, Voyager 1 will soon become the first spacecraft to officially leave the Solar System.

Or has it already left?

I won’t pretend I haven’t heard it before: Voyager 1 has left the Solar System! Usually followed soon after by: um, no it hasn’t. And while it might all seem like an awful lot of flip-flopping by supposedly-respectable scientists, the reality is there’s not a clear boundary that defines the outer limits of our Solar System. It’s not as simple as Voyager rolling over a certain mileage, cruising past a planetary orbit, or breaking through some kind of discernible forcefield with a satisfying “pop.” (Although that would be cool.)

The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)

Rather, scientists look at Voyager’s data for evidence of a shift in the type of particles detected. Within the transitionary zone that the spacecraft has most recently been traveling through, low-energy particles from the Sun are outnumbered by higher-energy particles zipping through interstellar space, also called the local interstellar medium (LISM). Voyager’s instruments have been detecting dramatic shifts in the concentrations of each for over a year now, unmistakably trending toward the high-energy end — or at least showing a severe drop-off in solar particles — and researchers from the University of Maryland are claiming that this, along with their model of a porous solar magnetic field, indicates Voyager has broken on through to the other side.

“It’s a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way,” said Marc Swisdak, UMD research scientist and lead author of a new paper published this week in The Astrophysical Journal Letters.

According to Swisdak, fellow UMD plasma physicist James F. Drake, and Merav Opher of Boston University, their model of the outer edge of the Solar System fits recent Voyager 1 observations — both expected and unexpected. In fact, the UMD-led team says that Voyager passed the outer boundary of the Sun’s magnetic influence, aka the heliopause… last year.

But, like some of last year’s claims, these conclusions aren’t shared by mission scientists at NASA.

“Details of a new model have just been published that lead the scientists who created the model to argue that NASA’s Voyager 1 spacecraft data can be consistent with entering interstellar space in 2012,” said Ed Stone, Voyager project scientist at Caltech, in a press release issued today. “In describing on a fine scale how magnetic field lines from the sun and magnetic field lines from interstellar space can connect to each other, they conclude Voyager 1 has been detecting the interstellar magnetic field since July 27, 2012. Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun.

The famous "Golden Record" carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA) — The famous “Golden Record” carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)

“Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble.”

Stone says that further discussion and investigation will be needed to “reconcile what may be happening on a fine scale with what happens on a larger scale.”

Whether still within the Solar System — however it’s defined — or outside of it, the bottom line is that the venerable Voyager spacecraft are still conducting groundbreaking research of our cosmic neighborhood, 36 years after their respective launches and long after their last views of the planets. And that’s something nobody can argue about.

“The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier.”

– Ed Stone, Voyager project scientist

Built by JPL and launched in 1977, both Voyagers are still capable of returning scientific data from a full range of instruments, with adequate power and propellant to remain operating until 2020.

Read the full UMD news release here, and find out more about the Voyager mission on the NASA/JPL website here.

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Note: The definition of “Solar System” used in this article is in reference to the Sun’s magnetic influence, the heliosphere, and all that falls within its outermost boundary, the heliopause (wherever that is.) Objects farther out are still gravitationally held by the Sun, such as distant KBOs and Oort Cloud comets, but orbit within the interstellar medium.

April 29, 2013April 26, 2016 by John Williams

Fly Along With Voyager

Fly along with NASA's Voyager spacecraft as the twin probes head towards interstellar space. In this artist's concept, a regularly updated gauge using data from the two spacecraft will indicate the levels of particles that originate from far outside our solar system and those that originate from inside our solar bubble. Those are two of the three signs scientists expect to see in interstellar space. The other sign is a change in the direction of the magnetic field. Image credit: NASA/JPL-Caltech

Far away, deep in the dark, near the edge of interstellar space, Voyager 1 and 2 are hurtling near the tenuous edge of the magnetic bubble surrounding the Sun known as the heliosphere and NASA wants you to ride along.

The Voyager website sports a new feature showing cosmic ray data. NASA’s Eyes on the Solar System, a popular Web-based interactive tool, contains a new Voyager module, that not only lets you ride along for the Voyagers’ journeys but also shows important scientific data flowing from the spacecraft.

[Warning:Play with this tool at your own risk. Interacting with this online feature can seriously impact your time; in an educational way, of course!]

As Voyager 1 explores the outer limits of the heliosphere, where the breath from our Sun is just a whisper, scientists are looking for three key signs that the spacecraft has left our solar system and entered interstellar space, or the space between stars. Voyager 1 began heading for the outer Solar System after zipping through the Saturn system in 1980.

The new module contains three gauges, updated every six hours from real data from Voyager 1 and 2, that indicate the level of fast-moving particles, slower-moving particles and the direction of the magnetic field. Fast-moving charged particles, mainly protons, come from distant stars and originate from outside the heliosphere. Slower-moving particles, also mainly protons, come from within the heliosphere. Scientists are looking for the levels of outside particles to jump dramatically while inside particles dip. If these levels hold steady, it means the Voyager spacecraft no longer feel the wind from our Sun and the gulf between stars awaits.

Over the past couple of years, data from Voyager 1, the most distant man-made object, show a steady increase of high-powered cosmic radiation indicating the edge is near, scientists say. Voyager 1 appears to have reached the last region before interstellar space. Scientists dubbed the region the “magnetic highway.” Particles from outside are streaming in while particles from inside are streaming out. Voyager 2’s instruments detect slight drops in inside particles but scientists don’t think the probe has entered the area yet.

Scientists also expect a change in the direction of the magnetic field. While particle data is updated every six hours, analyses of the magnetic field data usually takes a few months to prepare.

A snapshot riding along with Voyager 1's looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well. — A snapshot riding along with Voyager 1’s looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well.

Although launched first, Voyager 2 lags behind its twin Voyager 1 by more than 20 times the distance between the Earth and the Sun. Voyager 2 blasted off August 20, 1977 aboard a Titan-Centaur rocket from Cape Canaveral, Florida. The nuclear-powered craft visited Jupiter and Saturn with an additional mission, called the Grand Tour, to study Uranus and Neptune. Voyager 1 launched two weeks later on September 5, 1977. With a faster flight path, Voyager 1 arrived at Jupiter four months before its sister craft. Voyager 1 went on to study Saturn before using the ringed planet’s gravity field to slingshot it up and out of the plane of the solar system toward the constellation Ophiuchus, the Serpent Bearer.

NASA’s Eyes on the Solar System allows viewers to hitch a ride with any of NASA’s spacecraft as they explore the solar system. Time can be slowed for a near approach of a moon or asteroid or sped up to coast between the planets. Watch close at just the right moment and you can witness one of the spacecrafts roll maneuvers. All spacecraft movements are based on actual spacecraft navigation data.

Check out the Voyager module here, and check out the rest of the the Solar System here at Eyes on the Solar System.

March 20, 2013December 23, 2015 by Nancy Atkinson

Scientists Say Voyager 1 Has Left the Solar System, But Has It Really?

The edge of the solar system. Image Credit: NASA/JPL-Caltech

A new paper out today reports that the Voyager 1 spacecraft appears to have traveled beyond the influence of the Sun and exited the heliosphere. However, the data they cite is the same as what NASA Voyager scientists claimed in December 2012 was just a new region at the edge of the solar system that scientists previously didn’t know was there. They called it a “highway” of magnetic particles, shepherding Voyager 1 out into interstellar space, whereas the new paper put out by the American Geophysical Union says Voyager 1 has crossed a “heliocliff” and into interstellar space.

JPL spokesperson Jia-Rui Cook had just heard of the paper when Universe Today called this morning to verify the findings of the new paper. “Our last statement about this was the critical thing we were looking for was a change in the magnetic field data,” she said via phone. “This paper does not appear to address the magnetic field data.”

UPDATE: NASA has issued a statement regarding this issue:

“The Voyager team is aware of reports today that NASA’s Voyager 1 has left the solar system,” said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena, Calif. “It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space. In December 2012, the Voyager science team reported that Voyager 1 is within a new region called ‘the magnetic highway’ where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed.”

Cook told Universe Today that Voyager Project Scientist Ed Stone was out of the country, and she was trying to get in touch with him to verify the paper’s claims that Voyager has left the solar system, and he obviously wasted no time in setting the record straight.

In another update, the AGU reissued the press release with a different title to “to better represent the findings reported in the study.” The initial headline was “Voyager 1 Has Left the Solar System, Sudden Changes in Cosmic Rays Indicate,” and the new headline is “Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate.” So, basically, the new paper was just iterating the previous findings.

(End of updates)

The authors of the new paper, William Webber and F.B. McDonald, cite the events of last summer when Voyager 1 measured drastic changes in radiation levels, more than 18 billion km (11 billion miles) from the Sun. On July 28, 2012 the level of lower-energy particles originating from inside our Solar System dropped by half. However, in three days, the levels had recovered to near their previous levels. But then the bottom dropped out at the end of August, where anomalous cosmic rays (cosmic rays trapped in the outer heliosphere) all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays – cosmic radiation from outside of the solar system – spiked to levels not seen since Voyager’s launch, with intensities as much as twice previous levels.

“Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere,” said Webber in an AGU press release. Webber is a professor emeritus of astronomy at New Mexico State University in Las Cruces. He called this transition boundary the “heliocliff.”

In the Geophysical Research Letters article, the authors say, “It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium.”

However, last December in a NASA press conference, the Voyager team said they infered this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction of these magnetic field lines is predicted to change when Voyager breaks through to interstellar space.

“We believe this is the last leg of our journey to interstellar space,” Stone said during the press conference. “Our best guess is it’s likely just a few months to a couple years away. The new region isn’t what we expected, but we’ve come to expect the unexpected from Voyager.”

We’ll provide more information on this discrepancy between the interpretations of the events when we hear more from the Jet Propulsion Laboratory.

February 14, 2013December 23, 2015 by Jason Major

A Valentine From Voyager

Venus, Earth, Jupiter, Saturn, Uranus and Neptune as seen by Voyager 1 on Valentine's Day in 1990

On February 14, 1990, after nearly 13 years of travel through the outer Solar System, NASA’s Voyager 1 spacecraft crossed the orbit of Pluto and turned its camera around, capturing photos of the planets as seen from that vast distance. It was a family portrait taken from over 4.4 billion kilometers away — the ultimate space Valentine.

Who says astronomy isn’t romantic?

Full mosaic of Voyager 1 images taken on Feb. 14, 1990 (NASA/JPL)

“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives… There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”

– Carl Sagan

It was the unique perspective above provided by Voyager 1 that inspired Carl Sagan to first coin the phrase “Pale Blue Dot” in reference to our planet. And it’s true… from the edges of the solar system Earth is just a pale blue dot in a black sky, a bright speck just like all the other planets. It’s a sobering and somewhat chilling image of our world… but also inspiring, as the Voyager 1 and 2 spacecraft are now the farthest human-made objects in existence — and getting farther every second. They still faithfully transmit data back to us even now, over 35 years since their launches, from 18.5 and 15.2 billion kilometers away.

The Voyagers sure know the value of a long-term relationship.

See more news from the Voyager mission here.

February 3, 2013December 23, 2015 by Jason Major

We Are Made of Stardust

This brief quote by the late Carl Sagan is wonderfully illustrated in the beautiful and poignant short film “Stardust,” directed by Mischa Rozema of Amsterdam-based media company PostPanic. Using actual images from space exploration as well as CGI modeling, Stardust reminds us that everything we and the world around us are made of was created inside stars… and that, one day, our home star will once again free all that “stuff” back out into the Universe.

The film was made in memory of talented Dutch designer Arjan Groot, who died of cancer in July 2011 at the age of 39.

“I wanted to show the universe as a beautiful but also destructive place. It’s somewhere we all have to find our place within. As a director, making Stardust was a very personal experience but it’s not intended to be a personal film and I would want people to attach their own meanings to the film so that they can also find comfort based on their own histories and lives.”
– Mischa Rozema, director

A truly stunning tribute.

See more about this on PostPanic’s Vimeo page. (Credits after the jump.)

Credits:
A PostPanic Production
Written & directed by Mischa Rozema
Produced by Jules Tervoort
VFX Supervisor: Ivor Goldberg
Associate VFX Supervisor: Chris Staves
Senior digital artists: Matthijs Joor, Jeroen Aerts
Digital artists: Marti Pujol, Silke Finger, Mariusz Kolodziejczak, Dieuwer Feldbrugge, Cara To, Jurriën Boogert
Camera & edit: Mischa Rozema
Production: Ania Markham, Annejes van Liempd
Audio by Pivot Audio , Guy Amitai
Featuring “Helio” by Ruben Samama
Copyright 2013 Post Panic BV, All rights reserved

In the grand scheme of the universe, nothing is ever wasted and it finds comfort in us all essentially being Stardust ourselves. Voyager represents the memories of our loved ones and lives that will never disappear.

January 24, 2013December 23, 2015 by Jason Major

27 Years Ago: Voyager 2’s Visit to Uranus

Image of Uranus’ crescent taken by a departing Voyager 2 on January 25, 1986 (NASA/JPL)

27 years ago today, January 24, 1986, NASA’s Voyager 2 spacecraft sped past Uranus, becoming simultaneously the first and last spacecraft to visit the blue-tinged gas giant, third largest planet in the Solar System.

The image above shows the crescent-lit Uranus as seen by Voyager 2 from a distance of about 965,000 km (600,000 miles.) At the time the spacecraft had already passed Uranus and was looking back at the planet on its way outwards toward Neptune.

Although composed primarily of hydrogen and helium, trace amounts of methane in Uranus’ uppermost atmosphere absorb most of the red wavelengths of light, making the planet appear a pale blue color.

Image of the 1,500-km-wide Oberon acquired by Voyager 2 on Jan. 24, 1986 (NASA/JPL)

The second of NASA’s twin space explorers (although it launched first) Voyager 2 came within 81,800 kilometers (50,600 miles) of Uranus on January 24, 1986, gathering images of the sideways planet, its rings and several of its moons. Voyager 2 also discovered the presence of a magnetic field around Uranus, as well as 10 new small moons.

Three moons discovered by Voyager 2 in 1986 (NASA/JPL)

Data gathered by Voyager 2 revealed that Uranus’ rate of rotation is 17 hours, 14 minutes.

At the time of this writing, Voyager 2 is 15,184,370,900 km from Earth and steadily moving toward the edge of the Solar System at a speed of about 3.3 AU per year. At that distance, signals from Voyager take just over 14 hours and 4 minutes to reach us.

See images from Voyager 2’s visit of Uranus here, and check out a video of the August 20, 1977 launch below along with more images from the historic Voyager mission’s “Grand Tour” of the outer Solar System.

December 4, 2012December 23, 2015 by Nancy Atkinson

Voyager 1 Riding on a Magnetic Highway Out of the Solar System

Artist concept of NASA’s Voyager 1 spacecraft exploring a new region in our solar system called the “magnetic highway.” Credit: NASA/JPL-Caltech

The Voyager 1 spacecraft has not left the solar system, as was speculated earlier this year, but has now entered a new region at the edge of the solar system that scientists didn’t even know was there. It appears to be a “highway” of magnetic particles, shepherding Voyager 1 out into interstellar space.

“When you’ve gone where nothing has gone before, you expect to make new discoveries,” said Arik Posner, Voyager Program Scientist at a press briefing today.

“This is really another exciting step in the Voyager journey of exploration,” said Project Scientist Ed Stone. “Voyager’s discovered a new region of the heliosphere that we had not realized was there. It’s a magnetic highway where the magnetic field of the Sun is connected to the outside. So it’s like a highway, letting particles in and out.”

This artist’s concept shows plasma flows around NASA’s Voyager 1 spacecraft as it approaches interstellar space. Image credit: NASA/JPL-Caltech/JHUAPL

The heliosphere is a huge bubble of charged particles, and previously the Sun’s lower-energy charged particles have dominated. Now, Voyager 1 is in a region where it is surrounded almost entirely from cosmic rays from outside our solar system,as the lower-energy particles appear to be zooming out and higher-energy particles from outside are streaming in.

The first indication that something new was happening was on July 28 of this year when the level of lower-energy particles originating from inside our Solar System dropped by half. However, in three days, the levels had recovered to near their previous levels. But then the bottom dropped out at the end of August.

The two Voyager spacecraft have been heading outward since their launches 16 days apart in 1977. Voyager 1 is now near the edge of the solar system, and Voyager 2 is not far behind. Scientists feel this new region at the far reaches of our solar system is the final area the spacecraft has to cross before reaching interstellar space.

The Voyager team infers this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction of these magnetic field lines is predicted to change when Voyager breaks through to interstellar space.

“We believe this is the last leg of our journey to interstellar space,” Stone said. “Our best guess is it’s likely just a few months to a couple years away. The new region isn’t what we expected, but we’ve come to expect the unexpected from Voyager.”

Since December 2004, when Voyager 1 crossed a point in space called the termination shock, the spacecraft has been exploring the heliosphere’s outer layer, called the heliosheath. In this region, the stream of charged particles from the Sun, known as the solar wind, abruptly slowed down from supersonic speeds and became turbulent. Voyager 1’s environment was consistent for about five and a half years. The spacecraft then detected that the outward speed of the solar wind slowed to zero.

The intensity of the magnetic field also began to increase at that time.

“If we had only looked at the particle data alone, we would have said well, we’re out, goodbye solar system,” said Stamatios Krimigis, principal investigator for Voyager’s low-energy charged particle instrument. “We need to look at what all the instruments are telling us, because nature is very imaginative, and Lucy pulled out the football again.”

That’s because the magnetic field direction has not yet changed to the expected north-south orientation of interstellar space.

“We’re quite confident that there’s really no reason to believe we’re outside the heliosphere,” said Leonard Burlaga, with the Voyager magnetometer team. “There’s no evidence that we have entered the interstellar magnetic field. We are in a magnetic region unlike any we’ve been in before — about 10 times more intense than before the termination shock. The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space.”

As for the future of the spacecraft, which are powered by plutonium 238, they each lose about 4 watts of power a year and by 2020, the science team will have to start turning off instruments in order to conserve power. By 2025, there will probably not be enough power for any of the instruments to run, but there will be enough power to “ping” the spacecraft and have it answer. But by that time, they should be well out of the solar system. However, the spacecraft likely won’t encounter much, as it would take about 40,000 years for one of the Voyagers to reach another star system.

Voyager 1 is the most distant human-made object, about 18 billion kilometers (11 billion miles) away from the Sun. The signal from Voyager 1 takes approximately 17 hours to travel to Earth. Voyager 2, the longest continuously operated spacecraft, is about 15 billion kilometers (9 billion miles) away from our Sun. While Voyager 2 has seen changes similar to those seen by Voyager 1, the changes are much more gradual. Scientists do not think Voyager 2 has reached the magnetic highway.

Sources: Press briefing, JPL

October 8, 2012December 23, 2015 by Nancy Atkinson

Voyager 1 May Have Left the Solar System

Number of particles from the Sun hitting Voyager 1. Credit: NASA

While there’s no official word from NASA on this, the buzz around the blogosphere is that Voyager 1 has left the Solar System. The evidence comes from this graph, above, which shows the number of particles, mainly protons, from the Sun hitting Voyager 1 across time. A huge drop at the end of August hints that Voyager 1 may now be in interstellar space. The last we heard from the Voyager team was early August, and they indicated that on July 28, the level of lower-energy particles originating from inside our Solar System dropped by half. However, in three days, the levels had recovered to near their previous levels. But then the bottom dropped out at the end of August.

The Voyager team has said they have been seeing two of three key signs of changes expected to occur at the boundary of interstellar space. In addition to the drop in particles from the Sun, they’ve also seen a jump in the level of high-energy cosmic rays originating from outside our Solar System.

The third key sign would be the direction of the magnetic field. No word on that yet, but scientists are eagerly analyzing the data to see whether that has, indeed, changed direction. Scientists expect that all three of these signs will have changed when Voyager 1 has crossed into interstellar space.

“These are thrilling times for the Voyager team as we try to understand the quickening pace of changes as Voyager 1 approaches the edge of interstellar space,” said Edward Stone, the Voyager project scientist for the entire mission, who was quoted in early August. “We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space.”

Stone added that the data are changing in ways that the team didn’t expect, “but Voyager has always surprised us with new discoveries.”

Voyager 1 launched on Sept. 5, 1977, is approximately 18 billion kilometers (11 billion miles) from the Sun. Voyager 2, which launched on Aug. 20, 1977, is close behind, at 15 billion km (9.3 billion miles) from the Sun.

Sources: NASA, Eric Berger/ Houston Chronicle, Scientific American

September 18, 2012December 23, 2015 by Jason Major

35 Years Ago: Our First Family Portrait of the Earth and Moon

A crescent Earth and Moon as seen by Voyager 1 on September 18, 1977 (NASA)

35 years ago today, September 18, 1977, NASA’s Voyager 1 spacecraft turned its camera homeward just about two weeks after its launch, capturing the image above from a distance of 7.25 million miles (11.66 million km). It was the first time an image of its kind had ever been taken, showing the entire Earth and Moon together in a single frame, crescent-lit partners in space.

The view of Earth shows eastern Asia, the western Pacific Ocean and part of the Arctic. Voyager 1 was actually positioned directly above Mt. Everest when the images were taken (the final color image was made from three separate images taken through color filters.)

The Moon was brightened in the original NASA images by a factor of three, simply because Earth is so much brighter that it would have been overexposed in the images were they set to expose for the Moon. (Also I extended the sides of the image a bit above to fit better within a square format.)

Read the latest on Voyager 1: Winds of Change at the Edge of the Solar System

Previous images may have shown the Earth and Moon together, but they were taken from orbit around one or the other and as a result didn’t have both worlds fully — and in color! — within a single frame like this one does. In fact, it was only 11 years earlier that the very first image of Earth from the Moon was taken, acquired by NASA’s Lunar Orbiter I spacecraft on August 23, 1966.

It’s amazing to think what was happening in the world when Voyager took that image:
• World population was 4.23 billion (currently estimated to be 7.04 billion)
• The Space Shuttle Enterprise made its first test flight from a 747
• Star Wars, Close Encounters of the Third Kind and Saturday Night Fever were out in U.S. theaters
• Charlie Chaplin and Elvis Presley died
• U.S. federal debt was “only” $706 billion (now over $16 trillion!)
• And, of course, both Voyagers launched on their Grand Tour of the Solar System, ultimately becoming the most distant manmade objects in existence
(See more world stats and events here.)

Image: NASA/JPL

“Once a photograph of the Earth, taken from outside, is available – once the sheer isolation of the Earth becomes known – a new idea as powerful as any in history will be let loose.”
– Sir Fred Hoyle

September 7, 2012April 26, 2016 by Jason Major

Is Triton Hiding an Underground Ocean?

Voyager 2 mosaic of Neptune’s largest moon, Triton (NASA)

At 1,680 miles (2,700 km) across, the frigid and wrinkled Triton is Neptune’s largest moon and the seventh largest in the Solar System. It orbits the planet backwards – that is, in the opposite direction that Neptune rotates – and is the only large moon to do so, leading astronomers to believe that Triton is actually a captured Kuiper Belt Object that fell into orbit around Neptune at some point in our solar system’s nearly 4.7-billion-year history.

Briefly visited by Voyager 2 in late August 1989, Triton was found to have a curiously mottled and rather reflective surface nearly half-covered with a bumpy “cantaloupe terrain” and a crust made up of mostly water ice, wrapped around a dense core of metallic rock. But researchers from the University of Maryland are suggesting that between the ice and rock may lie a hidden ocean of water, kept liquid despite estimated temperatures of -97°C (-143°F), making Triton yet another moon that could have a subsurface sea.

How could such a chilly world maintain an ocean of liquid water for any length of time? For one thing, the presence of ammonia inside Triton would help to significantly lower the freezing point of water, making for a very cold — not to mention nasty-tasting — subsurface ocean that refrains from freezing solid.

In addition to this, Triton may have a source of internal heat — if not several. When Triton was first captured by Neptune’s gravity its orbit would have initially been highly elliptical, subjecting the new moon to intense tidal flexing that would have generated quite a bit of heat due to friction (not unlike what happens on Jupiter’s volcanic moon Io.) Although over time Triton’s orbit has become very nearly circular around Neptune due to the energy loss caused by such tidal forces, the heat could have been enough to melt a considerable amount of water ice trapped beneath Triton’s crust.

Another possible source of heat is the decay of radioactive isotopes, an ongoing process which can heat a planet internally for billions of years. Although not alone enough to defrost an entire ocean, combine this radiogenic heating with tidal heating and Triton could very well have enough warmth to harbor a thin, ammonia-rich ocean beneath an insulating “blanket” of frozen crust for a very long time — although eventually it too will cool and freeze solid like the rest of the moon. Whether this has already happened or still has yet to happen remains to be seen, as several unknowns are still part of the equation.

“I think it is extremely likely that a subsurface ammonia-rich ocean exists in Triton,” said Saswata Hier-Majumder at the University of Maryland’s Department of Geology, whose team’s paper was recently published in the August edition of the journal Icarus. “[Yet] there are a number of uncertainties in our knowledge of Triton’s interior and past which makes it difficult to predict with absolute certainty.”

Still, any promise of liquid water existing elsewhere in large amounts should make us take notice, as it’s within such environments that scientists believe lie our best chances of locating any extraterrestrial life. Even in the farthest reaches of the Solar System, from the planets to their moons, into the Kuiper Belt and even beyond, if there’s heat, liquid water and the right elements — all of which seem to be popping up in the most surprising of places — the stage can be set for life to take hold.

Read more about this here on Astrobiology.net.

Inset image: Voyager 2 portrait of Neptune and Triton taken on August 28, 1989. (NASA)