Lermontov Crater by VIRS

Today's video is a MASCS VIRS raster scan of Lermontov in Mercury's mid latitudes. Raster scans return a large number of spectra for targeted areas of interest. This movie was created from 258 VIRS spectra, taken 1 to 5 seconds apart. The VIRS color composite has been overlain on an MDIS image of Lermontov, showing that the crater center is red and thus brighter at longer wavelengths compared to the average Mercury terrain.

The VIRS composite shows hundreds of individual footprints tracks (minimum 100-200 m across and 3-4 km long) taken from different directions and altitudes. In locations where multiple footprints cover the same area, the footprint with the best illumination for mineralogical interpretation (usually the lowest incidence angle where shadows are minimized) is used for making the map.

Date Observed: August 8, 2013
Date Created: July 29, 2014
Instruments: Visible and Infrared Spectrograph (VIRS) of the Mercury Atmosphere and Surface Composition Spectrometer (MASCS) and Mercury Dual Imaging System (MDIS)
VIRS Color Composite Wavelengths: 575 nm as red, 415 nm/750 nm as green, 310 nm/390 nm as blue
Initial Latitude of Scan: 14.0°
Initial Longitude of Scan: 310.8° E
Final Latitude of Scan: 17.8°
Final Longitude of Scan: 310.0° E
Resolution: 0.25 km/pixel
Scale: Lermontov is 166 km (103 mi.) in diameter

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

Rembrandt Impact Basin Mineralogical Map

The top image is a MASCS VIRS color composite of Rembrandt, Mercury's second largest impact basin. The bottom image is a MDIS color mosaic of the same area. Rembrandt's rim appears blue in both images, indicating low reflectance relative to its center in the VIRS image. Some small, fresh craters appear in yellow and are highly reflective in VIRS.

The VIRS composite shows hundreds of individual footprints tracks (minimum 100-200 m across and 3-4 km long) taken from different directions and altitudes. In locations where multiple footprints cover the same area, the footprint with the best illumination for mineralogical interpretation (usually the lowest incidence angle where shadows are minimized) is used for making the map.

Date Created: July 27, 2014
Instruments: Visible and Infrared Spectrograph (VIRS) of the Mercury Atmosphere and Surface Composition Spectrometer (MASCS) and Mercury Dual Imaging System (MDIS)
VIRS Color Composite Wavelengths: 575 nm as red, 415 nm/750 nm as green, 310 nm/390 nm as blue
MDIS Color Wavelengths: 1000nm as red, 750nm as green, 430 as blue
Center Latitude: -34.3°
Center Longitude: 87.2° E
Resolution: 1 km/pixel
Scale: Rembrandt is 715 km (444 mi.) in diameter

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

Craters Eminescu, Xiao Zhao and Eastman by VIRS and MDIS

The top image is a MASCS VIRS interpolated color composite of craters Eminescu (center), with Xiao Zhao and Eastman toward the east and in Mercury's mid-latitudes. The bottom image is a monochrome MDIS mosaic of the same area. Yellow areas correspond to high values in both the red and green channels, that is, high reflectance (at 575 nm) and high values of the 415-nm/575-nm reflectance ratio. In some cases these spectral characteristics are associated with fresh material (like the rays of Xiao Zhao) that has been less affected by space weathering. Hollows, such as those found on and around the central peak of Eminescu, have similar colors.

The VIRS composite shows hundreds of individual footprints tracks (minimum 100-200 m across and 3-4 km long) taken from different directions and altitudes. In locations where multiple footprints cover the same area, the footprint with the best illumination for mineralogical interpretation (usually the lowest incidence angle where shadows are minimized) is used for making the map. In areas where footprints are sparse (separated by tens of km), observations are interpolated for complete coverage of the surface. In the MDIS mosaic, some brightness variations are due to tiling of images taken at different illuminations.

Date Created: June 16, 2014
Instruments: Visible and Infrared Spectrograph (VIRS) of the Mercury Atmosphere and Surface Composition Spectrometer (MASCS) and Mercury Dual Imaging System (MDIS)
VIRS Color Composite Wavelengths: 575 nm as red, 415 nm/750 nm as green, 310 nm/390 nm as blue
Center Latitude: 10.0°
Center Longitude: 114.3° E
Resolution: 1 km/pixel
Scale: Eminescu crater(center) is about 130 km (80 mi.) in diameter

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

Mercury by Messenger's MASCS and VIRS Instruments

The Sun's light provides a powerful tool for understanding the composition of materials in the Solar System. Today's image features two views of Mercury provided by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument. As the Sun's light hits the surface of Mercury, the Visible and Infrared Spectrograph (VIRS) portion of MASCS measures many wavelengths of the reflected light from a single spot on the surface at a time. These observations create a spectral profile of the surface as MESSENGER orbits Mercury. In each panel, the top left corner of the image is 70°N,180°E and the bottom right corner is 70°S,180°E. Most of Caloris basin can be seen along the right edge of each panel. The top panel is a monochromatic image of the interpolated 750 nm reflectance, and the bottom panel shows the same data but in a false color composite selected to highlight compositional variations on the surface.

The monochromatic map is part of a data set that was released to the public earlier this month through the Planetary Data System (PDS). In conjunction with the release, the team hosted a Data User's Workshop at the 45th Lunar and Planetary Science Conference, which is being held this week in The Woodlands, Texas.

Instruments: Visible and Infrared Spectrograph (VIRS) of the Mercury Atmosphere and Surface Composition Spectrometer (MASCS)
Center Latitude: 0°
Center Longitude: 0° E
Map Projection: Simple Cylindrical
VIRS Monochromatic Wavelength: 750 nm
VIRS Color Composite Wavelengths: 575 nm as red, 415 nm/750 nm as green, 310 nm/390 nm as blue
Scale: Caloris Basin is 1,550 km (963 mi) across.

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

Enhanced Color Map of Mercury

This colorful view of Mercury is similar to that used to generate this movie [23MB, 6.5MB] of Mercury as a spinning globe, and these two individual views (centered at 140°E and 320°E) of the innermost planet. The enhanced color view is overlaid on the global monochrome base map, which is available for download here.

The enhanced color was produced by using images from the color base map imaging campaign during MESSENGER's primary mission. These colors are not what Mercury would look like to the human eye, but rather the colors enhance the chemical, mineralogical, and physical differences between the rocks that make up Mercury's surface. This specific color combination places the second principal component in the red channel, the first principal component in the green channel, and the ratio of the 430 nm/1000 nm filters in the blue channel.

Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 0°
Center Longitude: 180° E
Map Projection: Simple cylindrical projection
Resolution: 3.74 km/pixel
Scale: Mercury's diameter is 4880 kilometers (3030 miles)

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

Mercury Global Map

A global color map of Mercury's surface has been created by mosaicking thousands of sets of images obtained by the MESSENGER Wide Angle Camera (WAC). The colors shown here are related to variations in the spectral reflectance across the planet. This view captures both compositional differences and differences in how long materials have been exposed at Mercury's surface. Young crater rays, arrayed radially around fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material," thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The large circular area near the top center is the Caloris impact basin, whose interior is filled with smooth, somewhat younger volcanic plains. Small orangish spots are materials deposited by explosive volcanic eruptions.

The color base map shown here consists of MDIS images taken through eight different color filters. It is part of a global color map that covers more than 99% of Mercury's surface with an average resolution of about 1 kilometer per pixel.

Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS). This is an enhanced-color presentation created from a statistical combination of images taken through eight of the WAC filters.

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

Note: Available on the original NASA webpage are two different size maps available for download: a smaller 6.5 MB video and a larger 23 MB video.

Mercury Spectral Reflectance Map

This sinusoidal equal area projection map shows a color composite of Mercury spectral reflectance observed by the MASCS VIRS instrument over the MESSENGER primary mission. VIRS footprint tracks are RGB-colored where red is brightness at 575 nm; green is the visible to infrared brightness ratio (415 nm / 750 nm); and blue is the ultraviolet to visible ratio (310 nm / 390 nm).

Broad regional differences and local areas of interest stand out with combinations of ratio and brightness values that give clues to mineralogical composition. Younger surface materials that are brighter at visible wavelengths and less affected by the processes of space weathering show up in reds, yellows and greens. Materials that may have relatively higher iron contents (though still very low relative to most lunar or terrestrial crustal rocks) show up in blues.

In locations where multiple VIRS footprints cover the same area, the footprint with the best illumination for mineralogical interpretation (usually the lowest incidence angle where shadows are minimized) is used for making the map.

Date Created: April 10, 2012
Instrument: Visible and Infrared Spectrograph (VIRS) of the MESSENGER Atmosphere and Surface Composition Spectrometer (MASCS)
Center Latitude: 0°
Center Longitude: 0° E
Resolution: 16 km/pixel

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

Hodgkins Crater in Color

We recently got a high-resolution look at Hodgkins crater. Today's featured image is a great example of how MDIS's two cameras complement each other: the NAC (narrow-angle camera) provides the high resolution and the WAC provides a lower resolution view in color. Usually the ejecta of fresh craters is relatively blue, but like Kuiper crater, Hodgkins continuous ejecta blanket is redder. In this case, it appears that Hodgkins has exposed a compositionally distinct material.

Date acquired: March 15, 2012
Image Mission Elapsed Time (MET): 240290904, 240290900, 240290896
Image ID: 1519152, 1519151, 1519150
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filters: 9, 7, 6 (996, 748, 433 nanometers) in red, green, and blue
Center Latitude: 28.60°
Center Longitude: 17.71° E
Resolution: 251 meters/pixel
Scale: Hodgkins crater (center) is approximately 18 km (11 miles) in diameter
Incidence Angle: 35.8°
Emission Angle: 12.6°
Phase Angle: 48.4°

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

Strange Hollows Discovered on Mercury

NASA's MESSENGER spacecraft has discovered strange hollows on the surface of Mercury. Images taken from orbit reveal thousands of peculiar depressions at a variety of longitudes and latitudes, ranging in size from 60 feet to over a mile across and 60 to 120 feet deep. No one knows how they got there.

"These hollows were a major surprise," says David Blewett, science team member from the Johns Hopkins University Applied Physics Laboratory. "We've been thinking of Mercury as a relic – a place that's really not changing much anymore, except by impact cratering. But the hollows appear to be younger than the craters in which they are found, and that means Mercury's surface is still evolving in a surprising way."

Mars Reconnaissance Orbiter spotted similar depressions in the carbon dioxide ice at Mars' south pole, giving that surface a "swiss cheese" appearance. But on Mercury they're found in rock and often have bright interiors and halos.

"We've never seen anything quite like this on a rocky surface."

If you could stand in one of these "sleepy" hollows on Mercury's surface, you'd find yourself, like Ichabod Crane, in a quiet, still, haunting place, with a black sky above your head.

"There's essentially no atmosphere on Mercury," explains Blewett. "And with no atmosphere, wind doesn't blow and rain doesn't fall. So the hollows weren't carved by wind or water. Other forces must be at work."

As the planet closest to the Sun, Mercury is exposed to fierce heat and extreme space weather. Blewett believes these factors play a role.

A key clue, he says, is that many of the hollows are associated with central mounds or mountains inside Mercury's impact craters. These so-called “peak rings” are thought to be made of material forced up from the depths by the impact that formed the crater. Excavated material could be unstable when it finds itself suddenly exposed at Mercury's surface.

"Certain minerals, for example those that contain sulfur and other volatiles, would be easily vaporized by the onslaught of heat, solar wind, and micrometeoroids that Mercury experiences on a daily basis," he says. "Perhaps sulfur is vaporizing, leaving just the other minerals, and therefore weakening the rock and making it spongier. Then the rock would crumble and erode more readily, forming these depressions."

MESSENGER has indeed proven Mercury unexpectedly rich in sulfur. That in itself is a surprise that's forcing scientists to rethink how Mercury was formed. The prevailing models suggest that either (1) very early in Solar System history, during the final sweep-up of the large planetesimals that formed the planets, a colossal impact tore off much of Mercury's rocky outer layering; or (2) a hot phase of the early Sun heated up the surface enough to scorch off the outer layers. In either case, the elements with a low boiling point – volatiles like sulfur and potassium – would have been driven off.

But they're still there.

"The old models just don't fit with the new data, so we'll have to look at other hypotheses."

To figure out how the planets and Solar System came to be, scientists must understand Mercury.

"It's the anchor at one end of the Solar System. Learning how Mercury formed will have major implications for the rest of the planets. And MESSENGER is showing that, up to now, we've been completely wrong about this little world in so many ways!"

What other surprises does Mercury hold? The sleepy hollows of the innermost planet may be just the beginning.

Photo credit (top):   NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington; (bottom):  Science/AAAS

Mapping Beethoven

At top, the white line highlights the region of Mercury's surface visible to the XRS during a solar flare on 16 June 2011. Near the center is the ~650-km-diameter Beethoven impact basin at 21° S, 236° E. This region has a higher Mg/Si ratio than the northern plains and is closer in composition to terrestrial komatiites, low-silica, high-temperature volcanic rocks that formed only very early in Earth's history.

Below, smooth plains within the same area have been mapped. In green are plains of volcanic origin. These plains display flooding and embayment relationships and color contrasts typical of volcanic plains on Mercury. Yellow denotes plains of uncertain origin. Though they may also be volcanic, they lack definitive evidence for a volcanic origin and may have formed as fluidized impact ejecta, possibly from the Beethoven impact basin, or as impact melt. In blue are plains that formed when rock was melted by impacts. Even geologically complex regions, such as the area seen here, are often dominated by volcanic deposits, and their compositions are consistent with a volcanic origin.

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

A Northern Footprint

The X-Ray Spectrometer (XRS) on MESSENGER collects compositional information for relatively large regions on Mercury's surface, and strong signals are only received during times of high solar activity. The blue region outlined in this wide-angle camera image mosaic shows the region visible to the XRS during a solar flare on 16 April 2011. The XRS data indicates that the area is basaltic in composition, the same type of volcanic rock that comprises the lunar maria. This region is part of the vast, high-reflectance northern plains that cover approximately 6% of Mercury's surface. The 1000, 750, and 430 nm bands of the Wide Angle Camera are displayed in red, green, and blue, respectively.

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