MESSENGER at Rest

In this perspective view, we look northwest over the Caloris Basin, a depression about 1500 km in diameter formed several billion years ago by the impact of a large projectile into the surface of Mercury. The mountain range at the edge of the basin can be seen as an arc in the background. In the foreground, we see a set of tectonic troughs, known as Pantheon Fossae, radiating from the center of the basin outward toward the edge of the basin interior. A 41-km-diameter impact crater, Apollodorus, is superposed just slightly off from the center of Pantheon Fossae. White and red are high topography, and greens and blues are low topography, with a total height differences of roughly 4 km. The MESSENGER spacecraft was launched in 2004 and ended it's orbital operations yesterday, April 30, 2015, by impacting Mercury's surface. Background image texture is provided by the Mercury Dual Imaging System (MDIS) instrument while color corresponds to surface elevation data obtained from the Mercury Laser Altimeter (MLA) experiment, with both draped over a digital elevation model derived from MLA altimetric data. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Goddard Space Flight Center

Speaking of signing off with a bang, because, you know, nobody really was, we might take a moment for MESSENGER:

Mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., confirmed today [30 April 2015] that NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the surface of Mercury, as predicted, at 3:26 p.m. EDT this afternoon (3:34 p.m. ground time).

MESSENGER Mission Complete: Final statistics for MESSENGER probe, which crashed into Mercury 30 April 2015 SCET.  Image from screenshot from mission page at Johns Hopkins University.Mission controllers were able to confirm the end of operations just a few minutes later at 3:40 p.m., when no signal was detected by the Deep Space Network (DSN) station in Goldstone, California, at the time the spacecraft would have emerged from behind the planet had MESSENGER not impacted the surface. This conclusion was independently confirmed by the DSN’s Radio Science team, who were simultaneously looking for the signal from MESSENGER from their posts in California.

MESSENGER was launched on August 3, 2004, and it began orbiting Mercury on March 18, 2011. The spacecraft completed its primary science objectives by March 2012. Because MESSENGER’s initial discoveries raised important new questions and the payload remained healthy, the mission was extended twice, allowing the spacecraft to make observations from extraordinarily low altitudes and capture images and information about the planet in unprecedented detail.

Last month — during a final short extension of the mission referred to as XM2′– the team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, 5 to 35 kilometers above the planet’s surface. On April 28, the team successfully executed the last of seven orbit-correction maneuvers (the last four of which were conducted entirely with helium pressurant after the remaining liquid hydrazine had been depleted), which kept MESSENGER aloft for the additional month, sufficiently long for the spacecraft’s instruments to collect critical information that could shed light on Mercury’s crustal magnetic anomalies and ice-filled polar craters, among other features.

With no way to increase its altitude, MESSENGER was finally unable to resist the perturbations to its orbit by the Sun’s gravitational pull, and it slammed into Mercury’s surface at around 8,750 miles per hour, creating a new crater up to 52 feet wide.

“Today we bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighboring planets,” said Sean Solomon, MESSENGER’s Principal Investigator and Director of Columbia University’s Lamont-Doherty Earth Observatory. “Our craft set a record for planetary flybys, spent more than four years in orbit about the planet closest to the Sun, and survived both punishing heat and extreme doses of radiation. Among its other achievements, MESSENGER determined Mercury’s surface composition, revealed its geological history, discovered that its internal magnetic field is offset from the planet’s center, taught us about Mercury’s unusual internal structure, followed the chemical inventory of its exosphere with season and time of day, discovered novel aspects of its extraordinarily active magnetosphere, and verified that its polar deposits are dominantly water ice. A resourceful and committed team of engineers, mission operators, scientists, and managers can be extremely proud that the MESSENGER mission has surpassed all expectations and delivered a stunningly long list of discoveries that have changed our views not only of one of Earth’s sibling planets but of the entire inner solar system.”

(Johns Hopkins University)

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EUNIS Solves a Solar Mystery

It is true that I have actually wondered about this. So it goes. Phil Plait offers a much more compelling explanation that I might:

The Sun’s atmosphere—its corona—is far, far hotter than its surface, and this has been a long-standing mystery, baffling astronomers for decades.Detail of image presented by James Klimchuk, Adrian Daw, Iain Hannah, and Stephen Bradshaw, 28 April 2015: "Millions of Tiny Explosions Cause the Sun's Corona".  Image shows small region of solar corona as seen by EUNIS, in the 10 million Kelvin superhot (teal), normal coronal 1 million Kelvin (pink) and lower atmosphere 100,000 Kelvin (yellow) ranges.

This week, astronomers announced they have found the smoking gun. Almost literally.

† † †

The thing is, while the photosphere is hot, roughly 5,500° C, the corona is freaking hot, 2 million degrees on average. That’s weird. Inside the Sun, the temperature drops as you move out from the center, but that trend reverses, viciously, at the corona.

Why is the corona so hot?

It really is a fascinating question, and is the sort of thing that allows us to ponder phrases like, “ten billion one megaton H-bombs”.

Nor should we overlook this detail:

This new breakthrough was made using several different observatories, including SOHO and the orbiting NuSTAR X-ray observatory (usually used to look at distant black holes, but which is also sensitive enough to see small-scale eruptions on the Sun). Interestingly, EUNIS was launched on a sounding rocket, a suborbital flight (basically, up-and-down) that lasted only 15 minutes! It’s amazing to think that in that short a time, such a long-standing mystery was finally solved.

We might call that a pretty darn good show.

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Image note: Detail of slideshow from Klimchuk, et al., “Millions of Tiny Explosions Cause the Sun’s Corona”, 28 April 2015, via Southwest Research Institute Planetary Science Directorate.

Plait, Phil. “A Million H-Bombs per Second Heat the Sun’s Corona”. Slate. 29 April 2015.

Linkadelica

NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. (22 Jan. 2015)

MylonasMcDonald-BasicColors-300pxSnowflakes

Colors

Gravity

Oppy’s Eleven

Marathon Oppy

Blowing stuff up for science

Nearer Ceres to Thee

Detail of 'xkcd' #1476, by Randall MunroeOh, yes. There is that.

What, you mean the mission where we chuck a metal box into space, fly it out to the asteroid belt, find a big rock, drop into orbit, survey the gravitational field and some other stuff, then kick out, maneuver through the storm of flying rocks, find another big rock, and do the whole orbit thing all over gain?

Yeah. That one.

Next stop, Ceres. ETA: 6 March 2015, SCET.

Say hello to Dawn.

No, really. This is already a great show. And it’s about to get even better.

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Munroe, Randall. “Ceres”. xkcd. 21 January 2015.

NASA. “DAWN: A Journey to the Beginning of the Solar System”. Jet Propulsion Laboratory. 2015.

NASA Van Allen Mission Finds Another Line of Planetary Defense

A cloud of cold, charged gas around Earth, called the plasmasphere and seen here in purple, interacts with the particles in Earth's radiation belts — shown in grey— to create an impenetrable barrier that blocks the fastest electrons from moving in closer to our planet. (Image Credit: NASA/Goddard)

Ozone hole got you down?α Maybe climate change is bringing just a bit too much sunshine and wrecking the grapes in your favorite wine?β Would you cheer up if we told you it could be worse?

Meanwhile, it is hard to imagine the private sector figuring certain things just for the sake of knowing. But, yes, it turns out that things really could be worse.

Two donuts of seething radiation that surround Earth, called the Van Allen radiation belts, have been found to contain a nearly impenetrable barrier that prevents the fastest, most energetic electrons from reaching Earth.

The Van Allen belts are a collection of charged particles, gathered in place by Earth’s magnetic field. They can wax and wane in response to incoming energy from the sun, sometimes swelling up enough to expose satellites in low-Earth orbit to damaging radiation. The discovery of the drain that acts as a barrier within the belts was made using NASA’s Van Allen Probes, launched in August 2012 to study the region. A paper on these results appeared in the Nov. 27, 2014, issue of Nature magazine.

“This barrier for the ultra-fast electrons is a remarkable feature of the belts,” said Dan Baker, a space scientist at the University of Colorado in Boulder and first author of the paper. “We’re able to study it for the first time, because we never had such accurate measurements of these high-energy electrons before.”

(Fox)

The more we understand about how the planet protects us against the Universe at large, the more we can learn about how to protect the planet against ourselves.

Pretty straightforward, that. But if you would like to know more about the Van Allen probes, there’s a mission page for that.

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α Yes, that still exists.

β A genuine challenge that is already here.

Fox, Karen C. “NASA’s Van Allen Probes Spot an Impenetrable Barrier in Space”. NASA Goddard Space Flight Center. 26 November 2014.

Astronomy and Human Progress

This morning, the National Radio Astronomy Observatory issued a press release, which in and of itself is hardly extraordinary. Its contents, however, are extraordinarily awesome:

ALMA image of the young star HL Tau and its protoplanetary disk. This best image ever of planet formation reveals multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF)

Astronomers have captured the best image ever of planet formation around an infant star as part of the testing and verification process for the Atacama Large Millimeter/submillimeter Array’s (ALMA) new high-resolution capabilities.

This revolutionary new image reveals in astonishing detail the planet-forming disk surrounding HL Tau, a Sun-like star located approximately 450 light-years from Earth in the constellation Taurus.

ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star.

“These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.

While this photo is not about to save a life or help a man improve his intimate relations, it occasionally occurs to us to remind that astronomy is not just about fancy photos. The human species needs astronomers.

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Art and Science … Again? Yes.

Visual effects in 'Interstellar' resulted in an astronomical discovery about black holes.

When it rains, it shines. Never mind. The variation fails the theme. Still, once again we find ourselves at a nexus of art and science.

Matt Williams of Universe Today explains:

Diagram by Kip Thorne, executive producer of the movie 'Interstellar', showing how a black hole distorts light.While he was working on the film Interstellar, executive producer Kip Thorne was tasked with creating the black hole that would be central to the plot. As a theoretical physicist, he also wanted to create something that was truly realistic and as close to the real thing as movie-goers would ever see.

On the other hand, Christopher Nolan – the film’s director – wanted to create something that would be a visually-mesmerizing experience. As you can see from the image above, they certainly succeeded as far as the aesthetics were concerned. But even more impressive was how the creation of this fictitious black hole led to an actual scientific discovery.

In short, in order to accurately create a visual for the story’s black hole, Kip Thorne produced an entirely new set of equations which guided the special effects team’s rendering software. The end result was a visual representation that accurately depicts what a wormhole/black hole would look like in space.

In truth, it is hard to imagine a better selling point for a science fiction film. Interstellar opens in American theaters November 7.

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Williams, Matt. “The Physics Behind ‘Intellstellar’s’ Visual Effects Was So Good, it Led to a Scientific Discovery”. Universe Today. 23 October 2014.

Postcard From the Middle of Nowhere

A snapshot of Rosetta and comet 67P/C-G, taken by Philae at a range of 16 km.

Rosetta is a spacecraft built and launched by the European Space Agency. Its travel partner is a robotic lander named Philae. Their job is to study a comet named 67P/Churyumav-Gearsimenko, or 67P/C-G for short.

The Rosetta mission launched in March, 2004. A little over a month ago, Rosetta and Philae quietly dropped into orbit around the massive comet.

European Space AgencyOn November 12, in little under a month, Philae will attempt to land on the comet.

Go, go human species! Philae, do the job; we’re all behind you.

Meanwhile, a holiday snap?

What you’re looking at in the picture above is none other than 67P/C-G; Philae took the snapshot, which includes part of the Rosetta structure, from a range of under ten miles

Elizabeth Howell, writing for Universe Today explains:

So this spacecraft — taking this picture — is going to land on the surface of THAT comet. Doesn’t this give you a pit in your stomach? This is a selfie taken from the Philae spacecraft that, riding piggyback, captured the side of the Rosetta spacecraft orbiting Comet 67P/Churyumov-Gerasimenko.

The image is so close-up — just 9.9 miles (16 kilometers) from 67P’s surface — that mission planners can even spot Landing Site J on the comet’s smaller lobe.

Additionally, Howell notes, we will hear tomorrow whether or not Site J is cleared for landing; the next data set will be gathered at a range of six miles away from 67p/C-G.

The article comes with a fun, attention grabbing headline, “Creepy Comet Looms In The Background Of Newest Philae Spacecraft Selfie”, but might well overstate the case. After all, when you two hundred ninety eight million miles from home, and all of ten miles away from the only thing in the Universe you can reach, yes, that thing might seem creepy. It’s four and a half miles long. Four miles wide. And it is two hundred ninety eight million miles out in the middle of nowhere and running away from you, yeah, that can be a heart-fluttering moment.

And yet our intrepid explorers push on. Good luck, Philae. And thank you, Rosetta. We know you’re not coming home, but we are so amazed.

And good show, ESA. As we creep toward the climax, we can only wait in thankful awe at the spectacle you’ve given us.

Location of Rosetta mission and comet 67P, 15 October SCET.

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European Space Agency. “Rosetta”. (n.d.)

Howell, Elizabeth. “Creepy Comet Looms In The Background Of Newest Philae Spacecraft Selfie”. Universe Today. 14 October 2014.

“Comet 67P (Churyumov-Gerasimenko) and The Rosetta Spacecraft”. Live Comet Data. 14 October 2014.

(Hat tip and many thanks to S.L.)