The End is Near: NASA’s MESSENGER Now Running on Fumes

The MESSENGER spacecraft has been in orbit around Mercury since March 2011. Image Credit: NASA/JHU APL/Carnegie Institution of Washington

For more than four years NASA’s MESSENGER spacecraft has been orbiting our solar system’s innermost planet Mercury, mapping its surface and investigating its unique geology and planetary history in unprecedented detail. But the spacecraft has run out of the fuel needed to maintain its extremely elliptical – and now quite low-altitude – orbit, and the Sun will soon set on the mission when MESSENGER makes its fatal final dive into the planet’s surface at the end of the month.

On April 30 MESSENGER will impact Mercury, falling down to its Sun-baked surface and colliding at a velocity of 3.9 kilometers per second, or about 8,700 mph. The 508-kilogram spacecraft will create a new crater on Mercury about 16 meters across.

The impact is estimated to occur at 19:25 UTC, which will be 3:25 p.m. at the John Hopkins University Applied Physics Lab in Laurel, Maryland, where the MESSENGER operations team is located. Because the spacecraft will be on the opposite side of Mercury as seen from Earth the impact site will not be in view.

Postcards from the (Inner) Edge: MESSENGER Images of Mercury

MESSENGER captures image of curious "hollows" around a crater peak
MESSENGER image of “hollows” around a crater’s central peak – one of the many unique discoveries the mission made about Mercury. Read more here.

But while it’s always sad to lose a dutiful robotic explorer like MESSENGER, its end is bittersweet; the mission has been more than successful, answering many of our long-standing questions about Mercury and revealing features of the planet that nobody even knew existed. The data MESSENGER has returned to Earth – over ten terabytes of it – will be used by planetary scientists for decades in their research on the formation of Mercury as well as the Solar System as a whole.

“For the first time in history we now have real knowledge about the planet Mercury that shows it to be a fascinating world as part of our diverse solar system,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate. “While spacecraft operations will end, we are celebrating MESSENGER as more than a successful mission. It’s the beginning of a longer journey to analyze the data that reveals all the scientific mysteries of Mercury.”

View the top ten science discoveries from MESSENGER here.

On April 6 MESSENGER used up the last vestiges of the liquid hydrazine propellant in its tanks, which it needed to make course corrections to maintain its orbit. But the tanks also hold gaseous helium as a pressurizer, and system engineers figured out how to release that gas through the complex hydrazine nozzles and keep MESSENGER in orbit for a few more weeks.

Earth and the Moon imaged by the MESSENGER spacecraft on Oct. 8, 2014
Earth and the Moon imaged by MESSENGER on Oct. 8, 2014. Credit: NASA/JHU APL/Carnegie Institution of Washington.

On April 24, though, even those traces of helium will be exhausted after a sixth and final orbit correction maneuver. From that point on MESSENGER will be coasting – out of fuel, out of fumes, and out of time.

“Following this last maneuver, we will finally declare MESSENGER out of propellant, as this maneuver will deplete nearly all of our remaining helium gas,” said Mission Systems Engineer Daniel O’Shaughnessy. “At that point, the spacecraft will no longer be capable of fighting the downward push of the Sun’s gravity.

“After studying the planet intently for more than four years, MESSENGER’s final act will be to leave an indelible mark on Mercury, as the spacecraft heads down to an inevitable surface impact.”

Read more: Five Mercury Secrets Revealed by MESSENGER

But MESSENGER scientists and engineers can be proud of the spacecraft that they built, which has proven itself more than capable of operating in the inherently challenging environment so close to our Sun.

“MESSENGER had to survive heating from the Sun, heating from the dayside of Mercury, and the harsh radiation environment in the inner heliosphere, and the clearest demonstration that our innovative engineers were up to the task has been the spacecraft’s longevity in one of the toughest neighborhoods in our Solar System,” said MESSENGER Principal Investigator Sean Solomon. “Moreover, all of the instruments that we selected nearly two decades ago have proven their worth and have yielded an amazing series of discoveries about the innermost planet.”

True color image of Mercury (MESSENGER)
True-color image of Mercury made from MESSENGER data. Credit: NASA/JHU APL/Carnegie Institution of Washington.

The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft launched on August 3, 2004, and traveled over six and a half years before entering orbit about Mercury on March 18, 2011 – the first spacecraft ever to do so. Learn more about the mission’s many discoveries here.

The video below was released in 2013 to commemorate MESSENGER’s second year in orbit and highlights some of the missions important achievements.

Source: NASA and JHUAPL

Are you an educator? Check out some teaching materials and shareables on the MESSENGER community page here.

Weekly Space Hangout – March 20, 2015: Lee Billings’ Five Billion Years of Solitude

Host: Fraser Cain (@fcain)
Special Guest: Author Lee Billings, discussing his book “Five Billion Years of Solitude”(@LeeBillings / leebillings.com/)
Guests:
Dr. Pamela Gay (cosmoquest.org / @starstryder)
Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg )
Brian Koberlein (@briankoberlein)
Continue reading “Weekly Space Hangout – March 20, 2015: Lee Billings’ Five Billion Years of Solitude”

Get a Change of View of Mercury’s North Pole

A forced perspective view of Profokiev crater near Mercury's north pole

It’s always good to get a little change of perspective, and with this image we achieve just that: it’s a view of Mercury’s north pole projected as it might be seen from above a slightly more southerly latitude. Thanks to the MESSENGER spacecraft, with which this image was originally acquired, as well as the Arecibo Observatory here on Earth, scientists now know that these polar craters contain large deposits of water ice – which may seem surprising on an airless and searing-hot planet located so close to the Sun but not when you realize that the interiors of these craters never actually receive sunlight.

The locations of ice deposits are shown in the image in yellow. See below for a full-sized version.

Perspective view of Mercury's north pole made from MESSENGER MDIS data.
Perspective view of Mercury’s north pole made from MESSENGER MDIS images and Arecibo Observatory data. (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

The five largest ice-filled craters in this view are (from front to back) the 112-km-wide Prokofiev and the smaller Kandinsky, Tolkien, Tryggvadottir, and Chesterton craters. A mosaic of many images acquired by MESSENGER’s Mercury Dual Imaging Sustem (MDIS) instrument during its time in orbit, you would never actually see a view of the planet’s pole illuminated like this in real life but orienting it this way helps put things into…well, perspective.

Radar observations from Arecibo showing bright areas on Mercury's north pole
Radar observations from Arecibo showing bright areas on Mercury’s north pole

Radar-bright regions in Mercury’s polar craters have been known about since 1992 when they were first imaged from the Arecibo Observatory in Puerto Rico. Located in areas of permanent shadow where sunlight never reaches (due to the fact that Mercury’s axial tilt is a mere 2.11º, unlike Earth’s much more pronounced 23.4º slant) they have since been confirmed by MESSENGER observations to contain frozen water and other volatile materials.

Read more: Ice Alert! Mercury’s Deposits Could Tell Us More About How Water Came To Earth

Similarly-shadowed craters on our Moon’s south pole have also been found to contain water ice, although those deposits appear different in composition, texture, and age. It’s suspected that some of Mercury’s frozen materials may have been delivered later than those found on the Moon, or are being restored via an ongoing process. Read more about these findings here.

Explore Mercury’s shadowed craters with the Water Ice Data Exploration (WIDE) app

In orbit around Mercury since 2011, MESSENGER is now nearing the end of its operational life. Engineers have figured out a way to extend its fuel use for an additional month, possibly delaying its inevitable descent until April, but even if this maneuver goes as planned the spacecraft will be meeting Mercury’s surface very soon.

Source: MESSENGER

Mercury Spacecraft’s 2015 Death Watch Could Go One More Month

Artist's impression of the MESSENGER spacecraft, with Mercury in the background. Credit: JHUAPL

If all goes well — and there’s no guarantee of this — NASA’s venerable Mercury sentinel may have an extra month of life left in it before it goes on a death plunge to the planet’s surface. Managers think they have found a way to stretch its fuel to allow the spacecraft to fly until April, measuring the planet’s magnetic field before falling forever.

Success will partially depend on a maneuver that will take place on Jan. 21, when MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) will raise its minimum altitude. But moreover, pushing the impact back to April will be the first extended test of using helium as a propellant in hydrazine thrusters, components that were not actually designed to get this done. But the team says it is possible, albeit less efficiently.

“Typically, when … liquid propellant is completely exhausted, a spacecraft can no longer make adjustments to its trajectory,” stated Dan O’Shaughnessy, a mission systems engineer with the Johns Hopkins University Applied Physics Laboratory.

“However, gaseous helium was used to pressurize MESSENGER’s propellant tanks, and this gas can be exploited to continue to make small adjustments to the trajectory.”

A crater on Mercury at the edge of the larger Oskison crater located in the plains north of Caloris basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
A crater on Mercury at the edge of the larger Oskison crater located in the plains north of Caloris basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

However long the mission does end up lasting, MESSENGER has shown us some unexpected things about the planet that is closest to the Sun. Turns out that water ice likely lies in some of the shadowed craters on its surface. And that organics, which were possibly delivered to Earth via comets and asteroids, are also on Mercury.

Atmospheric changes have been seen in the tenuous gases surrounding Mercury, showing a definite influence from the nearby Sun. And even the magnetic field lines on the planet are influenced by charged particles from our closest star.

And with MESSENGER viewing the planet from close-up, NASA and Johns Hopkins hope to learn more about volcanic flows, how crater walls are structured, and other features that you can see on the airless planet. Despite a 10-year mission and more than three years orbiting Mercury, it’s clear from MESSENGER that there is so much more to learn.

Source: Johns Hopkins University Applied Physics Laboratory

Name That Crater On Mercury! MESSENGER Team Opens Public Contest

The crater Scarlatti (at center) shines clearly in this image of Mercury taken by the MESSENGER spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Here’s your rare chance to leave a lasting mark on a piece of the Solar System. The team behind the MESSENGER spacecraft — that machine orbiting Mercury since 2011 — is asking the public to help them name craters on the planet, in an open contest.

Fifteen finalists will be forwarded to the official arbitrator of astronomical names on Earth, the International Astronomical Union, which will pick five names in time for the end of the MESSENGER mission this spring.

“This brave little craft, not much bigger than a Volkswagen Beetle, has travelled more than 8 billion miles [12.8 billion kilometers] since 2004—getting to the planet and then in orbit,” stated Julie Edmonds of the Carnegie Institution for Science, who leads the MESSENGER education and public outreach team.

A crater on Mercury at the edge of the larger Oskison crater located in the plains north of Caloris basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
A crater on Mercury at the edge of the larger Oskison crater located in the plains north of Caloris basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

“We would like to draw international attention to the achievements of the mission and the guiding engineers and scientists on Earth who have made the MESSENGER mission so outstandingly successful.”

Here are some guidelines to increase your chances of success:
– Make sure the name does not have significance politically, religiously or for the military;
– Focus on names of writers, artists and composers and research them thoroughly, as you will be expected to provide a justification;
– Don’t pick a name that has been used elsewhere in the Solar System.

Mercury's southern polar region as seen from MESSENGER. (Credit: NASA/Johns Hopkins UniversityApplied Physics Laboratory/Carnegie Institution of Washington).
Mercury’s southern polar region as seen from MESSENGER. (Credit: NASA/Johns Hopkins UniversityApplied Physics Laboratory/Carnegie Institution of Washington).

Some additional hints come from the official contest website, which adds that the competition is open to everyone except MESSENGER’s education and public outreach team and that entries close Jan. 15.

Impact craters are named in honor of people who have made outstanding or fundamental contributions to the Arts and Humanities (visual artists, writers, poets, dancers, architects, musicians, composers and so on). The person must have been recognized as an art-historically significant figure for more than 50 years and must have been dead for at least three years. We are particularly interested in submissions that honor people from nations and cultural groups that are under-represented amongst the currently-named craters.

This isn’t the first planet with recent open invitations for the public to name craters. Earlier this year, astronomy education group Uwingu began asking for suggestions to name craters on Mars for maps that will be used by the Mars One team as it plans to land a private crewed mission on the planet in the coming years. Those names, however, will likely not be recognized by the IAU (the official statement is here.)

Could Mercury Get A Meteor Shower From Comet Encke?

Artist's concept of the planet Mercury orbiting through a debris trail from Comet Encke that may cause a meteor shower. Credit: NASA's Goddard Space Flight Center

We’re sure going to miss the MESSENGER spacecraft at Mercury when it concludes its mission in 2015, because it keeps bringing us really unexpected news about the Sun’s closest planet. Here’s the latest: Mercury may get a periodic meteor shower when it passes through the debris trail of Comet Encke.

Why do scientists suspect this? It’s not from patiently watching for shooting stars. Instead, they believe the signature of calcium in Mercury’s tenuous atmosphere may be pointing to a pattern.

MESSENGER (which stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) has been orbiting the planet for three Earth years and sees regular “surges” in calcium abundance on a predictable schedule. The researchers suspect it’s because of bits of dust colliding with Mercury and ricocheting bits of calcium up from the surface.

Mercury also picks up bits of dust from interplanetary debris, but the scientists say it’s not enough to account for the amounts of calcium they see. Extrapolating, the researchers suspect it must occur as the planet passes through debris left behind from a comet or asteroid. There are a small number of such small bodies that do this, and the scientists narrowed it down to Encke.

Illustration of MESSENGER in orbit around Mercury (NASA/JPL/APL)
Illustration of MESSENGER in orbit around Mercury (NASA/JPL/APL)

Computer simulations of the comet’s debris showed a slight difference from what researchers predicted, but they believe it’s because of variations in Mercury’s orbit as it gets tugged by larger planets, particularly Jupiter. Encke itself takes about 3.3 years to do one lap around the Sun, and has been photographed by MESSENGER in the past.

“The possible discovery of a meteor shower at Mercury is really exciting and especially important because the plasma and dust environment around Mercury is relatively unexplored,” stated lead author Rosemary Killen, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland.

MESSENGER, meanwhile, is burning off the last of its fuel to stay in orbit; the final engine maneuver is expected for Jan. 21. Once that’s finished, the spacecraft will slowly spiral down towards the planet for an expected impact in March, ending the mission.

Source: NASA

Mercury Spacecraft Moves To Testing Ahead Of 2016 Launch To Sun’s Closest Planet

Artist's impression of the European Space Agency's BepiColombo mission in operation around Mercury. Credit: Astrium

After facing down a couple of delays due to technical difficulties, Europe’s and Japan’s first Mercury orbiter is entering some of the final stages ahead of its 2016 launch. Part of the BepiColombo orbiter moved into a European testing facility this past week that will shake, bake and otherwise test the hardware to make sure it’s ready for its extreme mission.

Because Mercury is so close to the Sun, BepiColombo is going to have a particularly harsh operating environment. Temperatures there will soar as high as 350 degrees Celsius (662 degrees Fahrenheit), requiring officials to change the chamber to simulate these higher temperatures. Time will tell if the spacecraft is ready for the test.

BepiColombo is also special because it includes not one orbiting spacecraft, but two. Flying in different orbits, the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter will try to learn more about this mysterious planet. NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) spacecraft has spent the past few  years orbiting Mercury, but before then, we had very little information on the planet. (And before MESSENGER, only brief flybys from NASA’s Mariner 10 in the 1970s turned up spacecraft-based information on Mercury.)

MESSENGER has turned up quite a few surprises. It’s showed us more about the nature of Mercury’s tenuous atmosphere and it’s discovered probable water ice (!) in permanently shadowed areas, among other things. The European Space Agency and Japan hope to push our understanding of the Sun’s closest planet when BepiColombo gets there in 2024.

On Oct. 30, 2014, the Mercury Planetary Orbiter (part of the BepiColombo mission) was moved into the European Space Agency's space simulator for testing ahead of the expected 2016 launch. Credit: ESA–A. Le’Floch
On Oct. 30, 2014, the Mercury Planetary Orbiter (part of the BepiColombo mission) was moved into the European Space Agency’s space simulator for testing ahead of the expected 2016 launch. Credit: ESA–A. Le’Floch

There are so many questions that Mercury presents us, and BepiColombo is trying to answer a few of those. For example, Mercury’s density is higher than the rest of the other terrestrial planets for reasons that are poorly understood. Scientists aren’t sure if its core is liquid or solid, or even it has active plate tectonics as Earth does. Its magnetic field is a mystery, given that Mars and Venus and the Moon don’t have any. And there are tons of questions too about its atmosphere, such as how it is produced and how the magnetic field and solar wind work together.

The two spacecraft will be carried together to Mercury’s orbit along with a component called the Mercury Transfer Model (MTM), which will push the spacecraft out there using solar-electric propulsion. Just before BepiColombo enters orbit, MTM will be jettisoned and the Mercury Polar Orbiter will ensure the Mercury Magnetospheric Orbiter receives the needed resources to survive until the two spacecraft move into their separate orbits, according to the European Space Agency.

As for why it takes so long to get out there, to save on fuel the mission will swing by Earth, Venus and Mercury to get to the right spot. Once the two spacecraft are ready to go, they’re expected to last a year in orbit — with a potential one-year extension.

Watch the “Blood Moon” Eclipse from Mercury

Earth and the Moon imaged by the MESSENGER spacecraft on Oct. 8, 2014

Yes, it’s another time-lapse of the October 8 lunar eclipse that was observed by skywatchers across half the Earth… except that these images weren’t captured from Earth at all; this was the view from Mercury!

The animation above was constructed from 31 images taken two minutes apart by the MESSENGER spacecraft between 5:18 a.m. and 6:18 a.m. EDT on Oct. 8, 2014.

“From Mercury, the Earth and Moon normally appear as if they were two very bright stars,” said Hari Nair, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, which developed and operates the MESSENGER mission for NASA. “During a lunar eclipse, the Moon seems to disappear during its passage through the Earth’s shadow, as shown in the movie.”

According to Nair the images have been zoomed by a factor of two and the Moon’s brightness has been increased by a factor of about 25 to enhance visibility. Captured by MESSENGER’s narrow-angle camera, Earth and the Moon were 0.713 AU (106.6 million km / 66.2 million miles) away from Mercury when the images were acquired.

Want to see some great photos of the eclipse shared by talented photographers around the world? Click here.

The Oct. 8 “Hunter’s Moon” eclipse was the second and last total lunar eclipse of 2014. The next will occur on April 4 of next year… but by that time MESSENGER won’t be around to witness it.

Launched August 3, 2004, MESSENGER entered orbit at Mercury on March 18, 2011. It is currently nearing the end of its missions as well as its its operational life, but we still have several more months of observations to look forward to from around the Solar System’s innermost planet before MESSENGER makes its final pass and ultimately impacts Mercury’s surface in March 2015.

Video credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Source: MESSENGER news release