Tag: Messenger

By comparing computer models with data gathered during the closest orbits of the Messenger spacecraft when it was in orbit around Mercury scientists have concluded that the planet’s inner core is solid like the Earth’s, though much larger than the Earth’s relative to the planet’s size.

Genova and his team put data from MESSENGER into a sophisticated computer program that allowed them to adjust parameters and figure out what the interior composition of Mercury must be like to match the way it spins and the way the spacecraft accelerated around it. The results showed that for the best match, Mercury must have a large, solid inner core. They estimated that the solid, iron core is about 1,260 miles (2,000 kilometers) wide and makes up about half of Mercury’s entire core (about 2,440 miles, or nearly 4,000 kilometers, wide). In contrast, Earth’s solid core is about 1,500 miles (2,400 kilometers) across, taking up a little more than a third of this planet’s entire core.

Using data gathered by the MESSENGER spacecraft while it was in orbit around Mercury, scientists now estimate that the planet’s crust is thinner than previously believed, 16 miles thick rather than 22 miles.

The crust is also as dense as aluminum. It is also the thinnest crust, relative to the planet’s core, of any rocky planet in the solar system.

Mercury’s core is believed to occupy 60 percent of the planet’s entire volume. For comparison, Earth’s core takes up roughly 15 percent of its volume. Why is Mercury’s core so large?

“Maybe it formed closer to a normal planet and maybe a lot of the crust and mantle got stripped away by giant impacts,” Sori said. “Another idea is that maybe, when you’re forming so close to the sun, the solar winds blow away a lot of the rock and you get a large core size very early on. There’s not an answer that everyone agrees to yet.”

There appears to be a great deal of uncertainty to these conclusions, and I would not be surprised if these conclusions change with the arrival of more data.

Using data from MESSENGER, scientists have found evidence that Mercury might still be tectonically active.

It appears that the last close-up images taken by the spacecraft before the mission ended discovered small thrust fault scarps that appeared very very fresh, suggesting they were formed recently, in geological time.

The science team for Messenger have now released a new digital elevation model of Mercury’s global surface.

The new product reveals a variety of interesting topographic features, as shown in the animation above, including the highest and lowest points on the planet. The highest elevation on Mercury is at 4.48 kilometers [2.78 miles] above Mercury’s average elevation, located just south of the equator in some of Mercury’s oldest terrain. The lowest elevation, at 5.38 kilometers [3.34 miles] below Mercury’s average, is found on the floor of Rachmaninoff basin, a basin suspected to host some of the most recent volcanic deposits on the planet.

If you watch the animation at the link, you will notice that the high points tend to cluster in the lower latitudes, while the low points tend to favor the high latitudes, suggesting a very slightly bulged shape, which is not surprising considering Mercury’s close proximity to the Sun.

The data release today also included an additional map showing the known geological features in more detail.

After four years in orbit around Mercury and eleven years in space, engineers have confirmed that Messenger has crashed into Mercury.

After four years in orbit and with its fuel gone, Messenger is now expected to crash into the surface of Mercury on April 30.

As Messenger dives closer and closer to Mercury as it prepares for its final impact on the planet’s surface sometime in the next few months, it has also completed its 4,000 orbit, four times longer than its original planned mission.

As Messenger nears the end of its lifespan orbiting Mercury, the project scientists have put together a slate of talks on what they have learned, presented today at the 46th annual Lunar and Planetary Science Conference in Houston.

The images that go with these presentations can be found here.

The image on the right is a close-up of the mysterious and unexpected hollows that Messenger found scattered everywhere on Mercury’s surface. According to today’s presentation, scientists now believe they are very recent features, formed when material with a lower boiling point evaporated away because of Mercury’s harsh and very hot environment. Imagine for example a vein of dry ice in a rock crack. The temperature rises above freezing and the dry ice evaporates. And like the convection bubbles in tomato sauce as it simmers, some of that evaporation pushes its way up by popping out a bubble and leaving behind a hollow.

In the case of Mercury the material is likely not dry ice, though scientists as yet are unsure what it is.

They are also presenting talks on magnesium on Mercury, the planet’s many scarps, and detailed observations of the permanently shadowed polar craters that might have water-ice in them.

As its fuel supplies begin to run out, engineers have used a new trick to raise Messenger’s orbit around Mercury in order to extend its research life.

The spacecraft’s orbit will still decay, and is expected to impact the surface sometime in the early spring of 2016.

Using Messenger, scientists think they have obtained optical images of the ice that is thought to exist in the permanently shadowed craters of Mercury.

Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC [Messenger’s camera] was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. “It worked in spectacular fashion,” said Chabot.

The team zeroed in on Prokofiev, the largest crater in Mercury’s north polar region found to host radar-bright material. “Those images show extensive regions with distinctive reflectance properties,” Chabot said. “A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters.” In other areas, water ice is present, she said, “but it is covered by a thin layer of dark material inferred to consist of frozen organic-rich compounds.” In the images of those areas, the dark deposits display sharp boundaries. “This result was a little surprising, because sharp boundaries indicate that the volatile deposits at Mercury’s poles are geologically young, relative to the time scale for lateral mixing by impacts,” said Chabot. [emphasis mine]

The image on the right is of the crater Kandinsky, and shows a very intriguing bright area on the crater’s central peak.

I highlighted that one word in the the scientist’s quote above to emphasize how preliminary these conclusions are. The images are intriguing, but I would not at this time bet a lot of money on these conclusions. Ice might be the best explanation for this data, at this time, but I would not be surprised at all if later research finds this conclusion to be false.

As Messenger continues its observations of Mercury engineers have now lowered its orbit to its closest approach yet, 62 miles.

They will lower the orbit even more in August and September, then raise it up again for its final few months of research at the innermost planet, after which the spacecraft will use its last fuel to impact the planet.

Having completed more than 3,000 orbits around Mercury, Messenger’s orbit is now being lowered to just under 125 miles from the surface.