2. Did Lava or Water Affect the Formation of Elysium Planitia?

3. *Gazetteer of Planetary Nomenclature*Gazetteer of Planetary Nomenclature, International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN), accessed January 31, 2014. Elysium Planitia is a large plain on the planet Mars. It covers an area of 3,000 km 2 (1,860 m 2 ). It is located at 2.98 N 154.74 E (center).* Source: dailygalaxy.com

4. Elysium Planitia is a volcanic region. It second in size only to the Tharsis region. There are three large volcanoes, which while smaller than the volcanoes in the Tharsis region, they are still large.* JPL Mars AtlasJPL Mars Atlas, accessed January 31, 2014. Source: NASA/JPL-Caltech

5. Elysium Mons is 9 km (5.6 miles) high and about 240 km (150 miles) in diameter. Like the volcanoes found at Tharsis, Elysium Mons “sits on a large pile of lava flows. This lets it rise 12 km [7.5 miles] above the mean planetary elevation.”* *Oregon State University – Volcano World*Oregon State University – Volcano World, accessed January 31, 2014.

6. On the northwestern edge of Elysium Mons, there are large channels from several valleys (grabens). They may have been formed when large volumes of water of subsurface water was released.* *Universe Today, Volcanoes on Mars by Jerry Coffey, June 4, 2008, accessed February 1, 2014.Volcanoes on Mars NASA/JPL-Caltech/Arizona State University.

7. Other volcanoes are found here. Hecates Tholus is 180 km (112 miles) across and 4.8 kilometers (3 miles) high. Albor Tholus is 150 km (93 miles) across and 4.1 km (2.5 miles) high.* *Coffey, Op. cit. Hecates Tholus and Albor Tholus (NASA/JPL-Caltech/Arizona State University )

8. It is possible that a frozen sea existed on Elysium Planitia. Geologists based this finding on ground patterns near Athabasca Vallis (1,180 km [730 miles] south of Elysium Planitia).* *The Encyclopedia of Science, Elysium Planitia*The Encyclopedia of Science, Elysium Planitia, accessed June 23, 2013. Image: NASA/JPL/University of Arizona

9. Evidence to support the possibility of flooding in its early history has been found by the Mars Reconnaissance Orbiter. “[T]he Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter detected flood channels that had been buried by lava flows in the Elysium Planitia region of Mars.” The lava flow effectively buried evidence of its older geologic history.* *Ancient Water Channels of Mars --The Elysium Planitia in 3-D*Ancient Water Channels of Mars --The Elysium Planitia in 3-D, Daily Galaxy, March 8, 2013, accessed October 15, 2013. Image – Daily Galaxy

10. THEMIS images indicate evidence of lava flows. A variegated mottled texture is readily apparent in this terrain located NW of the volcano, Elysium Mons. The Hrad Vallis (the Armenian word for Mars) channel system can be seen sauntering across the bumpy landscape of Utopia Planitia. The upper branch of Hrad Vallis has a large chunk of material on its floor; this chunk appears to have been rafted away from the material on the far left of the image (moved from left to right). This is unusual because the channel flows toward the left. This material may be lava flows. Many craters in this region of the planet have their interiors filled with material. Pedestal craters (craters with ejecta blankets perched higher than the surrounding plains) are also found in these regions. These observations seem to imply that this region was once buried and has now been uncovered (exhumed). The exact causes and timing of these events are unknown.

11. THEMIS images indicate evidence of lava flows. The dissected and eroded channel observed in this THEMIS image taken of the region southwest of the volcano Elysium Mons shows typical erosional islands and depositional features. The interesting thing about this channel is that it appears to start out of nowhere. The MOLA context image shows that the channel originates from a fissure within the ground, whose origin is likely volcanic, but may also be related to volatile ([of a substance] easily evaporated at normal temperatures) processes.

12. THEMIS images indicate evidence of lava flows. This VIS image shows just one of many lava channels located on the Elysium Mons volcanic complex.

13. THEMIS images indicate evidence of lava flows. This image shows several of the channels located in the Elysium Mons volcanic complex. It is likely that these channels were formed by lava flow rather than water.

14. THEMIS images indicate evidence of lava flows. The THEMIS image contains one large crater with layered details in the walls, and many smaller craters. One team went on to attempt to find the relative age of the Elysium Mons lava flow by comparing its crater count to the crater count of a known age lava flow on our own Moon.

15. THEMIS images indicate evidence of lava flows. The platy surface texture observed in this THEMIS image of the vast plains southeast of the volcano Elysium Mons likely formed by very fluid cooling lava. Variations in the surface texture may reflect different cooling or flow rates of the lava. The lack of any large impact craters also points to a relatively young age for these volcanic materials. The two largest impact craters occur in the higher plateau unit indicating that these materials are older.

16. While there is evidence of water in the surrounding area, volcanic lava flows are prevalent in the area. This leads to the conclusion that volcanic processes are responsible for the formation of Elysium Planatia.