02.08.2017 Mars Reconnaissance Orbiter Observes Changes
01.26.2017 Mono Lake
01.25.2017 'Wing' Dike of Hardened Lava in New Mexico
01.25.2017 Blade-Like Martian Walls Outline Polygons
01.23.2017 Spirit And Opportunity By The Numbers
01.10.2017 Mars 2020 Rover - Artist's Concept
01.06.2017 Earth and Its Moon, as Seen From Mars
12.13.2016 Now and Long Ago at Gale Crater, Mars
12.13.2016 Where's Boron? Mars Rover Detects It
11.15.2016 Schiaparelli Impact Site on Mars, Stereo
11.03.2016 Schiaparelli Impact Site on Mars, in Color
10.17.2016 MAVEN Captures Rapid Cloud Formation
10.17.2016 Mars' Nightside Atmosphere
10.17.2016 Ultraviolet Image Near Mars' South Pole
10.17.2016 Ultraviolet Mars Reveals Cloud Formation
10.05.2016 Dust Haze Hiding the Martian Surface in 2001
10.04.2016 Test of Lander Vision System for Mars 2020
10.03.2016 A Sharpened Ultraviolet View of Mars
10.03.2016 Curiosity Self-Portrait at 'Murray Buttes'
10.03.2016 Butte 'M9a' in 'Murray Buttes' on Mars
09.19.2016 Ribbon Cutting
09.09.2016 Farewell to Murray Buttes (Image 5)
09.09.2016 Farewell to Murray Buttes (Image 4)
09.09.2016 Farewell to Murray Buttes (Image 3)
09.09.2016 Farewell to Murray Buttes (Image 2)
09.09.2016 Farewell to Murray Buttes (Image 1)
08.26.2016 Out-of-this-World Records
08.04.2016 Mars Rover Is New Social Media Game
08.04.2016 Mars Rover Social Media Game
08.02.2016 Artist Concept for RIMFAX
07.20.2016 Viking 40 Year Anniversary Artwork: Medal
07.18.2016 Mars 2020 Range Trigger
07.14.2016 NASA to Launch Mars Rover in 2020
Meridiani PlanumWhen the Mars Exploration Rover, Opportunity, landed on Meridiani Planum in January 2004, it quickly found what it had been sent from Earth to find: evidence of liquid water in the Martian past.
Opportunity was targeted on Meridiani because remote sensing from orbit by the Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor showed that portions of Meridiani contain up to 20 percent gray crystalline hematite at the surface. Hematite is an iron-oxide mineral, and on Earth the gray crystalline variety forms mostly in association with liquid water.
On the ground, Opportunity discovered the hematite lies within BB-sized spherules, dubbed "blueberries" by scientists. Blueberries that litter the surface at the landing site are embedded within outcrops of soft, layered sandstone rocks.
As geologists reconstruct it, the blueberries formed when strongly acidic groundwater drenched the basaltic sandstone, which was rich in goethite, another iron-bearing mineral. The water altered the goethite into hematite, forming spherules within the rocks. Then, over unknown ages, as the acid-rotted sandstones weathered away, the tougher spherules came free and collected on the surface.
Image Credit: NASA/JPL-Caltech/Arizona State University