Mars Exploration Rover-B, also known as the Opportunity Rover, began its 16th year on Mars surface on 29 January. Since the beginning of its mission, Opportunity Rover set a record of distance travelled by wheeled vehicle outside Earth, travelled more than 45 kilometres and spent 511 Martian days working. Though it lost contact with Earth in June 2018, during its mission it made a lot of important discoveries.
Characterizing Martian geology
On Martian plains Opportunity found a lot different types of basalts that contained the minerals pyroxene, olivine, plagioclase, and magnetite. All the dust on Red Planet was thought to be magnetic, however it came up that magnetism was caused only by a few types of mineral magnetites.
Surprisingly, Opportunity found hematite-rich areas near planet’s equator. "Grey hematite is a mineral indicator of past water," said Dr. Joy Crisp, project scientist. "It is not always associated with water, but it often is." And that is why discovering hematite is so exciting.
Spherules and meteorites
Famous Martian “blueberries”, which are iron-rich spherules and are thought to be concretions created when water-borne minerals settled into sedimentary rock, where found a few weeks after beginning of the mission. Then in 2012 another type of spherule was found. Scientist called it "newberries” though its story remains unknown.
Despite finding Martian rocks Opportunity found a couple meteorites. The first one was discovered in 2005 and was the first meteor found outside Earth. Presence of heavy iron meteorites on surface implies a much denser Martian atmosphere in the past.
Collecting data about Mars' atmosphere and climate
The rover was equipped in APXS instrument to measure atmosphere on the planet and detect argon. Collected data allowed scientist to create a complete temperature profile. Another interesting thing is presence of Earth-like clouds, made of water and CO2. They can move quite fast and were qualified as cirrus. Opportunity’s data also explained how wind works in Mars atmosphere and how it moves sand. Sometimes dust changes sky colour from blue to red, depending on size and density of dust grains.
Astronomical observations impossible to make from Earth
The first that come to mind is taking a picture of Earth seen from Mars, though there are a couple more interesting observations. Thanks to Opportunity scientists followed transit of Mars moons across the Sun, lunar and solar eclipses from Red Planet’s surface. In January 2005 there was a transit of Mercury from Mars, though it wasn’t captured because of camera resolutions.
Researching Mars' past
Opportunity has gone backwards in time, to epoch when Mars was probably habitable. The most interesting evidence is this found in 2011 — a thin vein of gypsum that must had been deposited by liquid water billions of years ago along the rim of the Endeavour Crater. A year after that an area full of clay minerals (that implies presence of neutral water) was found in the same crater. "This is our first glimpse ever at conditions on ancient Mars that clearly show us a chemistry that would've been suitable for life at the Opportunity site," said Steve Squyres, mission principal investigator.
On June 10th 2018 Opportunity felt silent, after facing a massive dust storm. When the storm intensified, dust filled the Martian atmosphere, growing so thick that Opportunity couldn't harvest enough sunlight to recharge its batteries, and that’s why it turned out most devices. On September 20th NASA’s Mars Reconnaissance Orbiter sent a photo of silent rover, still located in Endeavour Crater.