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New Mysteries Unveiled on Mercury

The Rembrandt impact crater basin on Mercury.  Credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Smithsonian Institution/Carnegie Institution of Washington

The Rembrandt impact crater basin on Mercury. Credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Smithsonian Institution/Carnegie Institution of Washington


Even though Mercury looks like the Moon at first glance, scientists from the MESSENGER mission say it’s becoming apparent that Mercury is an amazingly dynamic planet, and is actually more like Mars. For example, before this mission, scientists weren’t sure if volcanism even existed on Mercury, but from the spacecraft’s two flybys, they now know it is a very important part of the planet’s history. Additional new findings from the second flyby of Mercury in October 2008 show that the planet’s atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.

And by the way, isn’t this a stunning picture of an impact basin? It’s one of the new discoveries from MESSENGER.

One of the most exciting results from the second flyby of Mercury is the discovery of a previously unknown large impact basin. The Rembrandt basin is more than 700 kilometers (430 miles) in diameter, and actually, to see the entire basin, it took combined images from both the first and second flyby to create the stunning picture above. Rembrandt is a relatively young impact basin, and forming about 3.9 billion years ago, is younger than any other known impact region on the planet. It shows pristine terrain on the outer portion of the crater, as well as unusual tectonic fault features, not found in any other big crater.

“This is the first time we’ve seen terrain exposed on the floor of an impact basin on Mercury that is preserved from when it formed” says MESSENGER scientist Thomas Watters. “Landforms such as those revealed on the floor of Rembrandt are usually completely buried by volcanic flows. We know that after Rembrandt formed, the planet was still contracting, so it is an exciting and unique new member of planetary craters we can study.”

MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, detected significant amounts of magnesium clumped in the planet’s tenuous atmosphere, called the exosphere. Scientists had suspected magnesium would be present, but were surprised at its distribution and abundance.

“Detecting magnesium was not too surprising, but what is surprising is the distribution and amounts of magnesium that was recorded,” said Bill McClintock, a MESSENGER co- investigator.
The instrument also measured other exospheric constituents during the October 6 flyby, including calcium and sodium, and he suspects that additional metallic elements from the surface including aluminum, iron, and silicon also contribute to the exosphere.

The differences in Mercury's magnetosphere in the two flybys by MESSENGER. Credit: Image produced by NASA/Goddard Space Flight Center/Johns Hopkins University Applied Physics Laboratory//Carnegie Institution of Washington. Image reproduced courtesy of Science/AAAS.

The differences in Mercury's magnetosphere in the two flybys by MESSENGER. Credit: Image produced by NASA/Goddard Space Flight Center/Johns Hopkins University Applied Physics Laboratory//Carnegie Institution of Washington. Image reproduced courtesy of Science/AAAS.


MESSENGER observed a radically different magnetosphere at Mercury during its second flyby, compared with its earlier January 14, 2008 encounter. In the first flyby, no dynamic features were found. But the second flyby was a totally different situation, said James Slavin, MESSENGER Co-Investigator.

“MESSENGER measured large magnetic flux leakage through the dayside magnetopause, about a factor of 10 greater than even what is observed at the Earth during its most active intervals. The high rate of solar wind energy input was evident in the great amplitude of the plasma waves and the large magnetic structures measured by the Magnetometer throughout the encounter.”

Slavin said Mercury’s magnetic field bears a marked resemblance to what we have at earth, but it is about 100 times weaker, which implies interior of Mercury is in part molten. “There is a dynamo action that is ongoing which regenerates and maintains the planetary magnetic field,” he said.

A subsurface interpretation of an impact basin on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington.

A subsurface interpretation of an impact basin on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington.


Scientists are also learning more abour Mercury’s crustal evolution, and have now mapped about 90% of the planet’s surface. About 40% is covered by smooth plains which are now known to be of volcanic origna. “These plains are globally distributed (in contrast with the Moon, which has a nearside/farside asymmetry in the abundance of volcanic plains),” said Brett Denevi, MESSENGER team member.

Data shows an enhanced iron- and titanium content in an ancient basin studied by MESSENGER, which are exposed on the surface only through impact events, and may formed when dense minerals settled out as they crystallized from a cooling magma. “There are a complex series of events going on here, but we see it everywhere, so this is a microcosm of the entire planet” said Denevi.

These discoveries are more clues to the mystery of the creation of the rocky, bizarre planet that resides closest to the sun.

Source: NASA Press conference, MESSNEGER press release

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • DrFlimmer May 14, 2009, 2:17 PM

    Well, Anaconda, I do agree on the last part of your last post!

    The question becomes how to distingish a fatal falsification (requiring complete rejection of the hypothesis) versus a non-fatal falsification (requiring only modification of the hypothesis)?

    I think this is the point where we start to differ (concerning some physical theories).

  • Anaconda May 14, 2009, 3:09 PM

    @ DrFimmer:

    I’m sure we do differ.

    So-called “dark” energy, and “dark” matter make up over 80% of the matter in the Universe.

    “It is an embarrassment that the dominant forms of matter in the universe remain hypothetical.” – – Jim Peebles, Princeton University

    This is what “modern” astronomy has come to? A complete reliance on theoretical abstracts because there is an absolute refusal to reconsider the basic premises of “modern” astronomy.

    In any self-respecting SCIENCE, other than some dog and pony show, a reliance on over 80% of the matter being an unknown placeholder that can’t be be detected would falsify the theory.

    FATAL FALSIFICATION.

    But not in “modern” astronomy.

    Laugh out loud.

    Oh, one other note Kristian Birkeland trained as a mathematician, but he knew experimenation was crucial to understanding.

    “We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture.” – – Hannes Alfvén, the father of Plasma Physics, Nobel prize winner 1970.

    Over 80% “dark” energy and matter — you can’t tell me “modern” astronomy has hasn’t gone completely astray into imaginary conjecture?

    Beware of misusing mathematics:

    “Ptolemaic epicycles are perhaps the most famous example of the dangers of the mathematical approach. They were a series of orbits within orbits designed to explain the motions of the planets, and with a few tweaks they would still work today. However, despite being mathematically correct – and indeed elegant – they failed to reflect the underlying reality.”

    And:

    “In another famous example, Scientific American ran an article ridiculing the alleged flights of the Wright Brothers … some years after they had been flying successfully! This pseudo-skepticism was based on the inertia of prior belief – that heavier than air flight was not possible. Needless to say, they had the math to prove that it was impossible, too.”

  • Nereid May 14, 2009, 3:57 PM

    [digression]Thus, using Anaconda’s own criterion, one of the most commonly mentioned Plasma Cosmology hypotheses is fatally falsified (Peratt’s idea about the formation of spiral galaxies and explanation of their rotation curves):

    If one test falsifies the hypothesis’ predictions then the hypothesis is required to be rejected or modified depending on the nature of the falsication.

    One falsification may require the rejection of the entire hypothesis depending on the nature of the falsification. Known as a fatal falsification.

    Other falsifications may require only the modification of the hypothesis.

    The question becomes how to distingish a fatal falsification (requiring complete rejection of the hypothesis) versus a non-fatal falsification (requiring only modification of the hypothesis)?

    The more different tests that falsify the predictions of the hypothesis, the more likely the entire hypothsis needs to be rejected.
    But single falsifications of predictions can require complete rejection of the hypothesis.

    [/digression]

    Thanks again for outlining the way you see these key terms Anaconda, I appreciate it.

    However, what I referred to by “theorized” relates to several of your own comments:

    Also, this quote from the article is highly problematic: “The discovery takes scientists a step further to determining the nature of dark matter, which remains a mystery since it was first discovered more than 70 years ago.”

    “[D]iscovered”???

    Don’t they mean theorized.

    “Dark matter” was not discovered “70 years ago, it was theorized 70 years ago. Big difference.

    Halton Arp indeed has studied many of these images where the quasar and the connected “parent” galaxy are connected by inter-galaxtic Birkeland currents, yet have different redshift values, Arp theorizes redshift is more an indication of age than distance, quasars being younger have a higher redshift according to Arp’s work. As I said before that contradicts the conventional assumptions about redshift — Arp has been studying quasars for over 30 years.

    What you wrote addresses 2), which I intend to not begin until we are done with 1).

    Here’s 2) again:

    2) developing an agreed and consistent set of objective criteria for deciding the extent to which a theory “matches observations and measurements” (to quote from one of his comments). This has been very much in the background to date, and the BA blog adds a key aspect: the extent to which “recognized physical properties which has been verified in the laboratory” must/should/can/might be added to the mix.

    Looking forward to your next comments …

  • Nereid May 14, 2009, 4:13 PM

    To add: the key thing I think we need to come to agreement on, Anaconda, wrt “theorized”, in the context of observation, detection, measurement, and inference is what distinguishes one from all the others.

    To take a concrete example: http://chandra.harvard.edu/photo/2002/0052/0052_xray_widefield.jpg

    The caption reads, in part “Chandra X-ray Image of Crab Nebula
    This image provides a dramatic look at the activity generated by the pulsar (white dot near the center of the image) in the Crab Nebula.

    I may be quite wrong, but I would guess that you, Anaconda, would say “… by the theorized pulsar (white dot near the center of the image) …

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