APOD: MESSENGER at Mercury (2011 Mar 31)

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APOD: MESSENGER at Mercury (2011 Mar 31)

Post by APOD Robot » Thu Mar 31, 2011 4:06 am

Image MESSENGER at Mercury

Explanation: On March 17, the MESSENGER spacecraft became the first to orbit Mercury, the solar system's innermost planet. This is its first processed color image since entering Mercury orbit. Larger, denser, and with almost twice the surface gravity of Earth's moon, Mercury still looks moon-like at first glance. But in this view its terrain shows light blue and brown areas near craters and long bright rays of material streaking the surface. The prominent bright ray crater Debussy at the upper right is 80 kilometers (50 miles) in diameter. Terrain toward the bottom of the historic image extends to Mercury's south pole and includes a region not previously imaged from space.

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by bystander » Thu Mar 31, 2011 4:08 am

MESSENGER: First Images from Mercury Orbit
http://asterisk.apod.com/viewtopic.php?f=29&t=23249
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by NoelC » Thu Mar 31, 2011 4:56 am

Very Moon-like indeed. What a lovely photo, and I'm sure looking forward to seeing many more (thanks for the link Bystander). Really takes you there and allows you to get to know Mercury.

Is the similarity in appearance perhaps because both are essentially erosion-free (lack of atmosphere, allowing the craters to accumulate over billions of years) and covered in fine gray metoritic dust of a similar nature?

Does Mercury have a magnetic field? Molten core? Is it made of similar stuff as the Moon/Earth?

Thanks, Messenger, for taking us there!

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Katleho mahase » Thu Mar 31, 2011 9:46 am

Its the most beautiful creation.

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Star*Hopper » Thu Mar 31, 2011 11:29 am

The length of the (Debussy) rays is remarkable. I'd almost bet they represent fractures rather than ejecta. Will be interesting to find if Mercury was ever in a 'brittle' state.
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by DLH » Thu Mar 31, 2011 11:47 am

The thing that attracts my attention is the crater to the left of Debussy, with two dark (ejecta?) streaks coming from it.

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by moonstruck » Thu Mar 31, 2011 11:50 am

Simply Fantastic.

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by acmuse » Thu Mar 31, 2011 12:18 pm

Is it possible to get telescopic images of Messenger itself against the face of Mercury?

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Thu Mar 31, 2011 12:36 pm

Star*Hopper wrote:
The length of the (Debussy) rays is remarkable. I'd almost bet they represent fractures rather than ejecta. Will be interesting to find if Mercury was ever in a 'brittle' state.
http://www.universetoday.com/84504/new-images-from-mercury-just-the-beginning-for-messenger-in-orbit/ wrote: <<This is a closeup Debussy Crater, which was the object of the first image released by MESSENGER yesterday. When asked about the age of this crater, [MESSENGER Principal Investigator Sean] Solomon said it is difficult to give a hard age to craters on Mercury due to not having samples in hand, like to do for the Moon. “On the moon ones that are bright like this, such as Copernicus, were formed in the last 20% in the history of the planet. We see only a handful of bright craters like Debussy on Mercury.”

“When you see a crater that is so bright,” Solomon continued, “ it is because it has not gone through the process of space weathering, completely. Brightness of craters identifies them as being younger than the rest of the terrain, as it hasn’t had the time to have their characteristics altered by age, as those of us with gray hair know.”

Solomon said Debussy was likely created by in impact of an object 5-10 km across. “Orbits of most asteroids and comets that encounter Mercury are traveling at a much higher speed than planetary bodies farther out from the Sun, and that shows in the amount of melt shown in the surface of Mercury. But still a lot we have to learn about that. Craters at different states of decay and degradation will tell us more about this.”>>
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by orin stepanek » Thu Mar 31, 2011 12:39 pm

How appropriate this APOD is! That picture was on the news last night. Hope a few more pictures of Mercury become available in the near future. 8-) :)
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Thu Mar 31, 2011 12:43 pm

acmuse wrote:
Is it possible to get telescopic images of Messenger itself against the face of Mercury?
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by JuanAustin » Thu Mar 31, 2011 12:58 pm

can you say in general or more specifically that most of the cratering we see on the rocky planets and moons throughout the solar system occured over a short period of time? do they all have that in common?
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Thu Mar 31, 2011 1:34 pm

JuanAustin wrote:
can you say in general or more specifically that most of the cratering we see on the rocky planets and moons throughout the solar system occured over a short period of time? do they all have that in common?
http://en.wikipedia.org/wiki/Late_Heavy_Bombardment wrote: <<The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a period of time approximately 4.1 to 3.8 billion years ago (Ga) during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well. The evidence for this event comes primarily from the dating of lunar samples, which indicates that most impact melt rocks formed in this rather narrow interval of time. While many hypotheses have been put forth to explain a "spike" in the flux of either asteroidal or cometary materials to the inner solar system, no consensus yet exists as to its cause. The Nice model popular among planetary scientists postulates that the gas giant planets migrated in orbit at this time, causing objects in the asteroid belt and/or Kuiper belt to be put onto eccentric orbits that reached the terrestrial planets. Nevertheless, some argue that the lunar sample data do not require a cataclysmic cratering event near 3.9 Ga, and that the apparent clustering of impact melt ages near this time is an artifact of sampling material affected by a single large impact basin.

The main piece of evidence for a lunar cataclysm comes from the radiometric ages of impact melt rocks that were collected during the Apollo missions. The majority of these impact melts are believed to have formed during the collision of asteroids or comets tens of kilometers across, forming impact craters hundreds of kilometers in diameter. The Apollo 15, 16, and 17 landing sites were chosen as a result of their proximity to the Imbrium, Nectaris, and Serenitatis basins.

Under study on Earth, the ages of impact melts collected at these sites clustered between about 3.8 and 4.1 Ga. The apparent clustering of ages of these was first noticed in the mid-1970s by Fouad Tera, Dimitri Papanastassiou, and Gerald Wasserburg who postulated that the ages record an intense bombardment of the Moon. They called it the "lunar cataclysm" and proposed that it represented a dramatic increase in the rate of bombardment of the Moon around 3.9 Ga. If these impact melts were derived from these three basins, then not only did these three prominent impact basins form within a short interval of time, but so did many others based on stratigraphic grounds. At the time, the conclusion was considered controversial [but] as more data has become available, particularly from lunar meteorites, this theory, while still controversial, has gained in popularity. The lunar meteorites are believed to randomly sample the lunar surface, and at least some of these should have originated from regions far from the Apollo landing sites. Many of the feldspathic lunar meteorites probably originated from the lunar far side, and impact melts within these have recently been dated. Consistent with the cataclysm hypothesis, none of their ages was found to be older than about 3.9 Ga. Nevertheless, the ages do not "cluster" at this date, but span between 2.5 and 3.9 Ga.

Studies of the highland crater size distributions suggest that the same family of projectiles struck Mercury and the Moon during late heavy bombardment. If the history of decay of late heavy bombardment on Mercury also followed the history of late heavy bombardment on the Moon, the youngest large basin discovered, Caloris, is comparable in age to the youngest large lunar basins, Orientale and Imbrium, and all of the plains units are older than 3 billion years.

Prior to the introduction of the Late Heavy Bombardment theory, it was generally assumed that the Earth had remained molten until about 3.8 Ga. This date could be found in all of the oldest known rocks from around the world, and appeared to represent a strong "cutoff point" beyond which older rocks could not be found. These dates remained fairly constant even across various dating methods, including the system considered the most accurate and least affected by environment, uranium-lead dating of zircons. As no older rocks could be found, it was generally assumed that the Earth had remained molten until this point in time, which defined the boundary between the earlier Hadean and later Archean eons.

Older rocks could be found, however, in the form of chips off asteroids that fall to Earth as meteorites. Like the rocks on Earth, asteroids also show a strong cutoff point, at about 4.6 Ga, which is assumed to be the time when the first solids formed in the protoplanetary disk around the then-young Sun. The Hadean, then, was the period of time between the formation of these early rocks in space, and the eventual solidification of the Earth's crust, some 700 million years later. This time would include the accretion of the planets from the disk and its slow cooling into a solid as the gravitational potential energy of this collapse was released. Later calculations showed that the rate of collapse and cooling was dependent on the size of the body, and applying this to an Earth-sized mass suggested this should have happened quite quickly, as quickly as 100 million years. The difference between measurement and theory was something of a mystery at the time.

The Late Heavy Bombardment is now offered as an explanation of this oddity. Under this model, the rocks dating to 3.8 Ga represent those that were solidifying after much of the crust was destroyed by the Bombardment. The Acasta Gneiss in the North American cratonic shield and gneisses within the Jack Hills portion of the Narryer Gneiss Terrane in Western Australia are, collectively, the oldest continental fragments on Earth and do not predate the late heavy bombardment. The oldest mineral yet dated on Earth, a zircon from Jack Hills, predates this event but may simply be a fragment of crust left over from this event, contained within a much younger (~3800 Ma old) rock. Some geologists believe they have found 4.28 billion year old rock in Quebec, Canada, though.

This has led to something of a revolution in the understanding of the earliest stages of Earth's history during the Hadean. Older references generally show the Hadean Earth having a molten surface with prominent volcanos, for instance Hadean time. The name referred to the "hellish" conditions assumed on Earth for the time. It is now believed that the Hadean surface was solid, temperate, and water covered (albeit acidic). This is due to the presence of several particular isotopic ratios which suggest water-based chemistry took place at some point prior to the formation of the oldest rocks.

Of particular interest, Manfred Schidlowski argued in 1979 that the carbon isotopic ratios of some sedimentary rocks found in Greenland were a relic of organic matter. There was much debate over the precise dating of the rocks, with Schidlowski suggesting they were about 3800 Ma old, and others suggesting a more "modest" 3600 Ma. In either case it was a very short time for abiogenesis to have taken place, and if Schidlowski was correct, arguably too short a time. The Late Heavy Bombardment and the "re-melting" of the crust that it suggests provides a timeline under which this would be possible; life either formed immediately after the Late Heavy Bombardment, or more likely survived it, having arisen earlier during the Hadean. Recent studies suggest that the rocks Schidlowski found are indeed from the older end of the possible age range at about 3850 Ma, suggesting the latter possibility is the most likely answer.>>
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Star*Hopper » Thu Mar 31, 2011 1:41 pm

JuanAustin wrote:can you say in general or more specifically that most of the cratering we see on the rocky planets and moons throughout the solar system occured over a short period of time? do they all have that in common?
~~~~
If you're theororizing, I'd venture much of it concerns the perspective from which one would define "a short period of time" relative to cosmological history.

Given that with the effects of gravitation and the orbits of bodies that would derive from same, I'd say "Yes", considering that most of the bodies that could have struck (causing craters) would have struck by now (relative to what craters now exist, or that we 'could' see (if possible) at this moment), and that following collisions would by nature be more 'strung out', resulting in fewer impacts as time progresses. That bolstered in that, basically speaking, as bodies upon impacting, reduce the population of bodies available for future collisions.

True that more bodies are created from collisions (et al) - aside from that, from the perspective of what we 'could' see, now.
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Star*Hopper » Thu Mar 31, 2011 1:44 pm

But Neufer's mouthful says it a lot better (while I was composing) than mine.
*LMAO*
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by biddie67 » Thu Mar 31, 2011 4:13 pm

I apologize for such a basic question but what does the unit "Ga" mean?

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by owlice » Thu Mar 31, 2011 4:20 pm

I had to Google for this...
Ga (for gigaannum), is a unit of time equal to 109 years (one billion on the short scale, one milliard on the long scale). It is commonly used in scientific disciplines such as cosmology and geology to signify extremely long time periods in the past. For example, the formation of the Earth occurred approximately 4.57 Ga (4.57 billion years) ago.
That from here: http://en.wikipedia.org/wiki/Year
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Thu Mar 31, 2011 6:13 pm

biddie67 wrote:
I apologize for such a basic question but what does the unit "Ga" mean?
I had to Google for this...
http://en.wikipedia.org/wiki/Lady_Gaga wrote: <<Lady Gaga was born Stefani Joanne Angelina Germanotta in New York City on March 28, 1986, the eldest child of Italian American Joseph Germanotta, an internet entrepreneur, and Cynthia. She learned to play piano from the age of four, went on to write her first piano ballad at 13 and began performing at open mike nights by age 14. Gaga came to prominence following the release of her debut studio album The Fame (2008), which was a commercial success and achieved international popularity with the singles "Just Dance" and "Poker Face". The album reached number one on the record charts of six countries, accomplished positions within the top-ten worldwide, and topped the Billboard Dance/Electronic Albums chart while simultaneously peaking at number two on the Billboard 200 chart in the United States. Achieving similar worldwide success, The Fame Monster (2009), its follow-up, produced a further two global chart-topping singles "Bad Romance" and "Telephone" and allowed her to embark on a second global headlining concert tour, The Monster Ball Tour, just months after having finished her first, The Fame Ball Tour. Her second studio album, Born This Way, is scheduled for release on May 23, 2011 after the arrival of its eponymous lead single "Born This Way" which achieved the number-one spot in countries worldwide and was the fastest-selling single in iTunes history, selling one million copies in five days.>>
University of Sydney astrophysicists are behind a major breakthrough in the study of stars known as red giants, finding a way to peer deep into their cores to discover which ones are in early infancy, which are fresh-faced teenagers, and which are facing their dying days.

The discovery, published in the latest edition of the journal Nature and made possible by observations using NASA's powerful Kepler space telescope, is shedding new light on the evolution of stars, including our own sun. Astronomer Travis Metcalfe of the US National Center for Atmospheric Research, in a companion piece in the same Nature issue which highlights the discovery's significance, compares red giants to Hollywood stars, whose age is not always obvious from the surface. "During certain phases in a star's life, its size and brightness are remarkably constant, even while profound transformations are taking place deep inside.">>

http://asterisk.apod.com/viewtopic.php?f=31&t=23266
Last edited by neufer on Thu Mar 31, 2011 6:29 pm, edited 1 time in total.
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Chris Peterson » Thu Mar 31, 2011 6:18 pm

biddie67 wrote:I apologize for such a basic question but what does the unit "Ga" mean?
The unit "a" means "year", or commonly "years ago". It may be prefixed with any of the standard SI multipliers- in this case, "G" for giga, meaning billion. So depending on context Ga either means a billion years, or a billion years ago.
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by biddie67 » Thu Mar 31, 2011 9:13 pm

((laughng )) based upon the neufer's submission above - i.e.,
.... compares red giants to Hollywood stars, whose age is not always obvious from the surface. "During certain phases in a star's life, its size and brightness are remarkably constant, even while profound transformations are taking place deep inside."
- does that mean that Lady Gaga is possibly "Ga squared" or Ga^2 years old??

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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Thu Mar 31, 2011 10:11 pm

biddie67 wrote:((laughng )) based upon the neufer's submission above - i.e.,
.... compares red giants to Hollywood stars, whose age is not always obvious from the surface. "During certain phases in a star's life, its size and brightness are remarkably constant, even while profound transformations are taking place deep inside."
- does that mean that Lady Gaga is possibly "Ga squared" or Ga^2 years old??
Possibly... Let's do some numbers:
http://en.wikipedia.org/wiki/Gigaannum#SI_prefix_multipliers wrote:
Click to play embedded YouTube video.
* Ma (for megaannum), is a unit of time equal to one million (106) years. It is commonly used in scientific disciplines such as geology, paleontology, and celestial mechanics to signify very long time periods into the past or future. For example, the dinosaur species Tyrannosaurus rex was abundant approximately 65 Ma (65 million years) ago (ago may not always be mentioned; if the quantity is specified while not explicitly discussing a duration, one can assume that "ago" is implied; the alternative but deprecated "mya" unit includes "ago" explicitly.). In astronomical applications, the year used is the Julian year of precisely 365.25 days.

* Ga (for gigaannum), is a unit of time equal to 109 years. It is commonly used in scientific disciplines such as cosmology and geology to signify extremely long time periods in the past. For example, the formation of the Earth occurred approximately 4.57 Ga ago.

* Ta (for teraannum), is a unit of time equal to 1012 years. It is an extremely long unit of time, about 70 times as long as the age of the universe. It is the same order of magnitude as the expected life span of a small red dwarf star.

* Pa (for petaannum), is a unit of time equal to 1015 years. The half-life of the nuclide cadmium-113 is about 8 Pa. This symbol coincides with that for the pascal without a multiplier prefix, though both are infrequently used and context will normally be sufficient to distinguish time from pressure values.

* Ea (for exaannum), is a unit of time equal to 1018 years. The half-life of tungsten-180 is 1.8 Ea.
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Star*Hopper » Thu Mar 31, 2011 11:54 pm

Uhhhh....I believe the numbers are more like this:
2(rah)+3(ah)+[(roma)+(roma+ma)]+2(ga)+(ooh)+2(la) = bad romance
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by Beyond » Fri Apr 01, 2011 12:10 am

:?:
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Fri Apr 01, 2011 9:16 am

DLH wrote:
The thing that attracts my attention is the crater to the left of Debussy, with two dark (ejecta?) streaks coming from it.
http://asterisk.apod.com/viewtopic.php?f=29&t=23249#p145831 wrote:
<<What is this dark material? Likely it is due to a dark type of rock on Mercury's surface, but there is not currently enough information to identify the type of rock. However, with MESSENGER now in orbit, that situation will soon change, as MESSENGER's orbital science campaign will provide unprecedented chemical information about the rock types on Mercury's surface.>>
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Re: APOD: MESSENGER at Mercury (2011 Mar 31)

Post by neufer » Fri Apr 01, 2011 6:03 pm

acmuse wrote:
Is it possible to get telescopic images of Messenger itself against the face of Mercury?
http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=448 wrote: <<Of Interest: MESSENGER captured this image while taking one of its first pictures from orbit around the planet Mercury. The frame shown is one of several images obtained of the same view through the different color filters of the Mercury Dual Imaging system (MDIS) Wide Angle Camera (WAC).

The first reaction of some on the MESSENGER team was that the feature to the left of Mercury’s limb must be an imaging artifact. “It’s the effect of solar neutrinos on the WAC’s CCD,” pronounced Project Scientist Mack Knott. The imaging team was skeptical of this explanation, however, and all Knott could add was “I could explain it to you, but you’d have to understand Feynman diagrams.”

The imaging team brought the anomalous image to the attention of Mission Systems Engineer E. Finn Again, who immediately called an emergency gathering of the Collision Avoidance Review Board. Fortunately, the unusual object in the image did not appear to be in the immediate path of MESSENGER’s next few orbits, but the fact that earlier and subsequent images of the same scene did not include the object prevented a determination of its trajectory.

One of MESSENGER’s Science Team members, Prof. S. T. Rom, recognized the object immediately as Mariner 10, the only spacecraft before MESSENGER to have visited Mercury. Launched in 1973, Mariner 10 flew by Mercury three times in 1974 and 1975 before communication with the probe was lost. Prof. Rom is the only member of the MESSENGER team to have served on the science team of Mariner 10 as well.

The Science Operations Center was filled at the time with MESSENGER team members, and everyone proceeded at once to theorize on why Mariner 10 might appear in an MDIS image of Mercury.

Professor Rom suggested that Mariner 10 may have remained in place as of the time of its last signal:

[list]“Day after day, day after day,
We stuck, nor breath nor motion;
As idle as a painted ship
Upon a painted ocean.”[/list][/color][/i]
The dead albatross hanging from Rom’s neck, however, reduced the effectiveness of his argument.

Mission design lead Mick Adams quickly calculated that Mariner 10 should not be encountering Mercury on this date. “Mariner 10 and Mercury were in a resonant state that brought the spacecraft by the planet once every two Mercury years. By my calculation, this appearance is 23 days early.”

Guidance and control lead E. C. Shaughn offered that the effect of solar radiation should have substantially altered Mariner 10’s orbit over the past 36 years as a result of solar sailing:

[list]“With throats unslaked, with black lips baked,
We could nor laugh nor wail;
Through utter drought all dumb we stood!
I bit my arm, I sucked the blood,
And cried, A sail! a sail!”[/list][/color][/i]
Propulsion lead Brecht Engel added that some residual propellant after Mariner 10’s last propulsive maneuver may have outgassed, and that multiple outgassing events may also have contributed to trajectory changes:

[list] “A speck, a mist, a shape, I wist!
And still it neared and neared:
As if it dodged a water-sprite,
It plunged and tacked and veered.”[/list][/color][/i]
MESSENGER’s navigation team members, all of whom are named Williams, plugged these suggestions into their codes. Minutes later they were able to announce to all assembled that Mariner 10 appeared to be in a new resonant state, one synchronous with Earth’s period. The ancient spacecraft is locked into an orbit that swings it by Mercury once every Earth year, on April 1st.

As MESSENGER passed into eclipse behind Mercury, Prof. Rom had the last word:
  • “The sun's rim dips; the stars rush out:
    At one stride comes the dark;
    With far-heard whisper o'er the sea,
    Off shot the spectre-bark.”
    >>
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