Category: Mercury

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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.

“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.

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

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Scientists from the MESSENGER mission to Mercury discussed today the results from the spacecraft’s October 6 flyby of the closest planet to the sun. The probe has produced several science firsts and is returning hundreds of new photos and measurements of the planet’s surface, atmosphere and magnetic field. The images show a battered surface, and we now have pictures and data of parts of Mercury’s surface that have never been examined by a spacecraft. “The region of Mercury’s surface that we viewed at close range for the first time this month is bigger than the land area of South America,” said Sean Solomon, principal investigator and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. “When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95 percent of the planet.”

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or MESSENGER, spacecraft flew by Mercury shortly after 4:40 a.m. EDT, on Oct. 6. It completed a critical gravity assist to keep it on course to orbit Mercury in 2011 and unveiled 30 percent of Mercury’s surface never before seen by a spacecraft.

The spacecraft’s science instruments operated throughout the flyby. Cameras snapped more than 1,200 pictures of the surface, while topography beneath the spacecraft was profiled with a laser altimeter. The comparison of magnetosphere observations from the spacecraft’s first flyby in January with data from the probe’s second pass has provided key new insight into the nature of Mercury’s internal magnetic field and revealed new features of its magnetosphere. The magnetosphere is the volume surrounding Mercury that is controlled by the planet’s magnetic field.

It was discovered that the planet’s magnetic field is highly symmetric.

The probe’s Mercury Laser Altimeter, or MLA, measured the planet’s topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.

“The MLA collected altimetry in regions where images from MESSENGER and Mariner 10 data are available, and new images were obtained of the region sampled by the altimeter in January,” said Maria Zuber, co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology. “These topographic measurements now improve considerably the ability to interpret surface geology.”

The Mercury Atmospheric and Surface Composition Spectrometer observed Mercury’s thin atmosphere, known as an exosphere. The instrument searched for emissions from sodium, calcium, magnesium, and hydrogen atoms. Observations of magnesium are the first detection of this chemical in Mercury’s exosphere. Preliminary analysis suggests that the spatial distributions of sodium, calcium, and magnesium are different. Simultaneous observations of these spatial distributions, also a first for the spacecraft, have opened an unprecedented window into the interaction of Mercury’s surface and exosphere.

Spacecraft images also are revealing for the first time vast geologic differences on the surface.

“Now that MESSENGER’s cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the moon and Mars, Mercury’s surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins,” said co-investigator Mark Robinson of Arizona State University in Tempe.

Source: NASA

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Here’s the first image from MESSENGER’s flyby of Mercury on Monday. The bright crater just south of the center of the image is Kuiper, which has been seen before on images from the Mariner 10 mission in the 1970s. But most of this image, to the east, or right of Kuiper, toward the limb of Mercury is new territory for human eyes – at least in optical views. The image was taken by the Wide Angle Camera as MESSENGER was departing from the planet, and are among the first spacecraft views of that portion of Mercury’s surface. Most striking are the large pattern of rays that extend from north to south, almost along the entire face of Mercury. Amazing! This extensive ray system appears to emanate from a relatively young crater newly imaged by MESSENGER, providing a view of the planet distinctly unique from that obtained during MESSENGER’s first flyby.

2nd Update: (9:40 am CDT) More images!

Update: (8:50 am CDT) See 2nd image released below:

Above is the 3rd image released from the second flyby, a spectacular close-up of Mercury, as seen by the MESSENGER as it approached the planet, at about 17,100 kilometers (10,600 miles) altitude. The features in the foreground, near the right side of the image, are close to the terminator, the line between the sunlit dayside and dark night side of the planet, so shadows are long and prominent. The MESSENGER team has only had a few hours to examine these intriguing features, and, currently, more images from the flyby are still streaming back to Earth.

Here’s the second image released from the flyby. This is a close-up image taken 9 minutes and 14 seconds after MESSENGER’s closest approach to Mercury, when the spacecraft was moving at 6.1 kilometers/second (3.8 miles/second). The largest impact feature at the top of the image is about 133 kilometers (83 miles) in diameter and is named Polygnotus. This area was imaged previously by Mariner 10.

More on the first image: Data from the flyby started coming back to Earth early this morning, at about 1:50 am EDT. This spectacular image is one of the first to be returned and was taken about 90 minutes after the spacecraft’s closest approach to Mercury. This young, extensively rayed crater, along with the prominent rayed crater to the southeast of Kuiper, near the limb of the planet, were both seen in Earth-based radar images of Mercury but not previously imaged by spacecraft. As the MESSENGER team is busy examining this newly obtained view that is only a few hours old, data from the flyby continue to stream down to Earth, including higher resolution close-up images of this previously unseen terrain.

MESSENGER completed the flyby on Oct. 6 at 4:40 am EDT.

We’ll add more images as they become available.

Source: MESSENGER Gallery