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It's been awhile since I dropped a thread o' #Mars, so let's try something different today... 
1. The hues of #Mars' surface are generally thanks to dust cover—or (relative) lack thereof. Lighter areas = dusty, darker = less dusty.
Oh wow, y'all act fast—I will try to keep up! 😝
2. #Mars has dust storms, but not like "The Martian." 🙂 The storms lift fine dust into the air; takes awhile for them to settle out.
3. Mars doesn't appear to have had plate tectonics. Earth seems to be the only place in the Solar System that does!
4. Mars has huge volcanoes, including Olympus Mons, the tallest in the Solar System. But none have been active for >100 million years.
5. Most of Mars' volcanoes haven't been active for MUCH longer—100 million years is estimate of youngest lava flow.
6. Valles Marineris is often called the largest "canyon" in the Solar System. But it's actually a series of "chasmata." (Img: @Cornell)
7. These chasmata likely formed separately & then coalesced as they grew over time.
8. Valles Marineris was named for the mission that discovered it, Mariner 9, which arrived at Mars in 1971.
9. The first successful mission to Mars, Mariner 4, flew by in 1965. Its images...weren't stunning. 😝 Mariner Crater is named in its honour.
10. You can see a surprising amount of detail on Mars with even a poor quality telescope—Huygens spotted Syrtis Major & S polar cap in 1659!
11. While Lowell is famous for his "canals" on Mars, the idea of them wasn't widely accepted by the scientific community in his day.
12. Grab your 3D glasses! Lots of Mars has been buried & then exhumed (un-buried). This crater is one example.
13. Gale Crater, where @MarsCuriosity currently lives, is another example of a buried -> exhumed crater.
14. Mars's surface is red due to iron oxide. But if you get below the rusty dust, it's often not red at all!
15. When Spirit's right front wheel stopped working, it serendipitously dug a trench that exposed nearly pure silica—evidence of past water.
16. The Phoenix lander dug a small trench at its northern high latitude landing site on Mars, revealing buried ice!
17. Newly-formed impact craters on Mars blast away the dust on the surface around them, revealing the underlying darker nature of Mars.
18. The south polar cap of Mars, made of CO2 ice, is mysteriously eroding away. The northern polar cap, made of water ice, seems stable.
19. For the Canadians out there: Mount Sharp in Gale Crater, which @MarsCuriosity is scaling right now, is as tall as 10 CN Towers! 🇨🇦
20. Because this can never be shared enough: @MarsCuriosity took images as it was landing & the result was AWESOME:
22. Also can't be shared enough: The @HiRISE camera aboard NASA's Mars Reconnaissance Orbiter captured @MarsCuriosity as it was landing!
[INTERMISSION: Meeting time. Back in a bit!]
23. We've sent ground penetrating radar instruments to Mars, which see the internal structure of the polar caps. This is the northern cap.
24. Mars Global Surveyor + Mars Recon. Orbiter have been monitoring Mars' weather for years! Weekly weather reports:
msss.com/msss_images/la…
msss.com/msss_images/la…
25. In May of 2003, Mars Global Surveyor imaged #Jupiter & some of its moons from orbit around Mars.
26. On the same day as #25, Mars Global Surveyor also imaged Earth and the Moon from orbit around Mars.
27. Most years on #ValentinesDay, Malin Space Science Systems releases a captioned image of a new "heart" on Mars.
28. The "Face on Mars" imaged by Viking is a trick of illumination. Didn't look much like a face to Mars Global Surveyor.
29. Mars Global Surveyor managed to snap a pic of a fellow orbiter, Mars Odyssey, in 2005!
30. Mars has dust devils, like certain places on Earth. We've seen them from orbit and from rovers on the surface.
31. Martian dust devils leave dark "tracks" in their wake where they've removed dust from the planet's surface. Looks like abstract art.
32. Dust devils on Mars have helpfully cleaned the solar panels of Opportunity multiple times, helping it keep powered to keep on roving!
34. Mars Odyssey had a gamma ray spectrometer aboard, which detects hydrogen—a proxy for near-surface H2O (water) ice. It found a lot of it!
35. We've found multiple new impact craters that have excavated buried ice on Mars in the mid/high latitudes (>40°N).
36. @corginaut found a buried ice deposit in Mars' mid-latitudes the size of Lake Superior!
nasa.gov/feature/jpl/ma…
nasa.gov/feature/jpl/ma…
37. Mars has a lot of things that look like glaciers. Thanks to ground penetrating radar, buried ice was confirmed in some of them!
38. Mars also has ice on its surface in the form of frost—both carbon dioxide and water. It deposits on the surface around wintertime.
39. The Phoenix lander captured this lovely view of early morning water-ice frost on the martian surface during its mission.
40. Viking 2 also saw water frost on the martian surface.
41. Spirit, Opportunity, and Curiosity have all spotted iron meteorites on the martian surface during their rovings.
42. Volcanism on Mars was driven by "hot spots" similar to the Hawaiian volcanoes on Earth.
43. This paint-by-numbers drawing was the very first image from Mars (by @mikamckinnon via @Gizmodo):
gizmodo.com/this-paint-by-…
gizmodo.com/this-paint-by-…
44. Yep! (Not counting the Moon as a planet here obviously.)
45. I stand corrected—under good conditions & w/the right equipment you can see Mercury's surface too.
46. Craters <60 km diameter on Mars are named for towns on Earth w/population <100,000. This is Penticton, after a town in British Columbia.
47. Craters >60 km diameter on Mars are named after scientists or sci-fi authors w/martian significance. This is Lowell Crater, 203 km diam.
48. More of #Canada on Mars: One of the geologic units studied by @MarsCuriosity in Gale Crater is named Yellowknife Bay. 🇨🇦
49. More #Canada on Mars: @csa_asc funded the Alpha Particle X-Ray Spectrometer (APXS) aboard @MarsCuriosity. 🇨🇦
50. Even more #Canada on Mars: The Meteorological Station (MET) aboard the Phoenix lander was Canada's 1st visit to the martian surface. 🇨🇦
Going to disconnect for the night and hand the reins to @SpaceProfessor2 for a bit to give you some historical & pop culture Mars facts!
