The MESSENGER spacecraft acquired this image of Mercury on January 23, 2015, at a time when this part of Mercury was near sunset. It’s one of the highest-resolution images yet obtained of Mercury. The area shown is 6.3 kilometers / 3.9 miles wide. It’s located within what is called the Hokusai Quadrangle in the northern hemisphere on Mercury. The image shows terraces on a west-facing crater wall. The terracing forms just after the crater is excavated by the impact, and the walls are too steep to support themselves, causing slumping.
This is an image from the NAC low-altitude, high-resolution imaging campaign. Click here to see the full-resolution image.
The MESSENGER mission has been a huge and unqualified success. Launched on August 3, 2004, this valiant little spacecraft completed an Earth flyby, 2 Venus flybys and 3 Mercury flybys before orbital insertion around Mercury on March 18, 2011. As it is now running low on the propellant needed for course adjustments, MESSENGER will soon suffer orbital decay and ultimately is destined to crash into Mercury.
On September 12, 2014 the spacecraft periherm – its closest point to Mercury – was successfully raised from: 24.3 kilometers / 15.1 miles to 94 kilometers / 58.4 miles, extending the mission further.
Periherm was raised on October 24, 2014 from 26 kilometers / 16.1 miles to 185.2 kilometeres / 115.1 miles.
You can see that Mercury keeps getting close to Mercury, but its controllers, so far, have been able to raise its orbit again.
On January 21, 2015, periherm was raised again from 25.7 kilometers / 16 miles to 105.1 kilometers / 65.3 miles, using the remainder of the fuel and a little of the helium pressurant.
MESSENGER was expected to impact Mercury on the weekend of March 28 or 29, 2015. An unexpected bonus of using unused helium from the pressurant system may delay impact to late April 2015, with a final helium pressurant thrust now planned for March 18, 2015 – the fourth anniversary of its orbital insertion around Mercury – performing the final-ever periherm raise maneuver.
Bottom line: One of the highest-resolution images ever obtained of the sun’s innermost planet, Mercury. The valiant MESSENGER spacecraft acquired the image on January 23, 2015.
Andrew R. Brown, an avid follower of the space program, writes frequently about space topics for EarthSky. Over several years, he has also suggested observations that were carried out by imaging teams of some space missions. He has lives in Ashford, Kent, United Kingdom and works for local government, Kent County Council.