Slowly but surely the mysteries of dwarf planet Ceres are being peeled back layer by layer as NASA’s Dawn spacecraft orbits lower and lower and gathers detailed measurements that have now yielded global mineral and topographic maps, tantalizing researchers with the best resolution ever.
The Dawn science team has been painstakingly stitching together the spectral and imaging products captured from the lowest orbit yet achieved into high resolution global maps of Ceres, released today Sept. 30, by NASA.
“Ceres continues to amaze, yet puzzle us, as we examine our multitude of images, spectra and now energetic particle bursts,” said Chris Russell, Dawn principal investigator at the University of California, Los Angeles, in a statement.
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The color coded map above is providing researchers with valuable insights into the mineral composition of Ceres surface, as well as the relative ages of the surface features that were a near total mystery until Dawn arrived on March 6, 2015.
The false-color mineral map view combines images taken using infrared (920 nanometers), red (750 nanometers) and blue (440 nanometers) spectral filters.
“Redder colors indicate places on Ceres’ surface that reflect light strongly in the infrared, while bluish colors indicate enhanced reflectivity at short (bluer) wavelengths; green indicates places where albedo, or overall brightness, is strongly enhanced,” say officials.
“Scientists use this technique in order to highlight subtle color differences across Ceres, which would appear fairly uniform in natural color. This can provide valuable insights into the mineral composition of the surface, as well as the relative ages of surface features.”
Researchers say the mineral variations at Ceres “are more subtle than on Vesta, Dawn’s previous port of call.”
The asteroid Vesta was Dawn’s first orbital target and conducted extensive observations of the bizarre world for over a year in 2011 and 2012.
The Dawn team is meeting this week to review and publish the mission results so far at the European Planetary Science Conference in Nantes, France.
Dawn is Earth’s first probe in human history to explore any dwarf planet, the first to explore Ceres up close and the first to orbit two celestial bodies.
Ceres is a Texas-sized world, ranks as the largest object in the main asteroid belt between Mars and Jupiter, and may have a subsurface ocean of liquid water that could be hospitable to life.
The newly released maps were created from data gathered at Dawn’s current science orbit, known as the High Altitude Mapping Orbit (HAMO) phase of the mission, during August and September.
At HAMO, Dawn is circling Ceres at an altitude of barely 915 miles (1,470 kilometers) above the heavily cratered surface.
“Dawn arrived in this third mapping orbit [HAMO] on Aug. 13. It began this third mapping phase on schedule on Aug. 17,” Dr. Marc Rayman, Dawn’s chief engineer and mission director based at NASA’s Jet Propulsion Laboratory, Pasadena, California, told Universe Today.
Each HAMO mapping orbit cycle lasts 11 days and consists of 14 orbits lasting 19 hours each. Ceres is entirely mapped during each of the 6 cycles. The third mapping cycle started on Sept. 9.
Dawn’ instruments, including the Framing Camera and Visible and Infrared Spectrometer (VIR) will be aimed at slightly different angles in each mapping cycle allowing the team to generate stereo views and construct 3-D maps.
“The emphasis during HAMO is to get good stereo data on the elevations of the surface topography and to get good high resolution clear and color data with the framing camera,” Russell told me.
“We are hoping to get lots of VIR IR data to help understand the composition of the surface better.”
“Dawn will use the color filters in its framing camera to record the sights in visible and infrared wavelengths,” notes Rayman.
The new maps at HAMO provide about three times better resolution than the images captured from its previous orbit in June, and nearly 10 times better than in the spacecraft’s initial orbit at Ceres in April and May.
The science team also released a new color-coded topographic map annotated with over a dozen Cerean feature names recently approved by the IAU.
“The names for features on Ceres are all eponymous for agricultural spirits, deities and festivals from cultures around the world. These include Jaja, after the Abkhazian harvest goddess, and Ernutet, after the cobra-headed Egyptian harvest goddess. A 12-mile (20-kilometer) diameter mountain near Ceres’ north pole is now called Ysolo Mons, for an Albanian festival that marks the first day of the eggplant harvest.”
The biggest Cerean mystery of all remains the nature of the bright spots at Occator crater. It’s still under analysis and the team released a new color coded topographic map.
The imagery and other science data may point to evaporation of salty water as the source of the bright spots.
“Occasional water leakage on to the surface could leave salt there as the water would sublime,” Russell told me.
“The big picture that is emerging is that Ceres fills a unique niche,” Prof. Chris Russell, Dawn principal investigator told Universe Today exclusively.
“Ceres fills a unique niche between the cold icy bodies of the outer solar system, with their rock hard icy surfaces, and the water planets Mars and Earth that can support ice and water on their surfaces,” said Russell.
“The irregular shapes of craters on Ceres are especially interesting, resembling craters we see on Saturn’s icy moon Rhea,” says Carol Raymond, Dawn’s deputy principal investigator based at NASA’s Jet Propulsion Laboratory, Pasadena, California. “They are very different from the bowl-shaped craters on Vesta.”
Dawn was launched on September 27, 2007 by a United Launch Alliance (ULA) Delta II Heavy rocket from Space Launch Complex-17B (SLC-17B) at Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.