1 00:00:01,920 --> 00:00:06,480 Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey 2 00:00:06,519 --> 00:00:10,560 Speaker 1: brain Stuff, Lauren Bogelbaum. Here. You'd like to think you 3 00:00:10,640 --> 00:00:13,600 Speaker 1: know your neighbors, but sometimes they'll catch you off guard. 4 00:00:14,520 --> 00:00:17,840 Speaker 1: That diminutive world called Mercury is the first planet from 5 00:00:17,840 --> 00:00:20,919 Speaker 1: our Sun, Venus's second, Earth is the third, and dear 6 00:00:20,920 --> 00:00:25,119 Speaker 1: old Mars is number four common knowledge, but that numbering 7 00:00:25,280 --> 00:00:28,720 Speaker 1: obscures certain truths. With its tight orbit around the Sun, 8 00:00:28,960 --> 00:00:32,000 Speaker 1: Mercury can't ventures far away from Earth as Venus and 9 00:00:32,040 --> 00:00:36,040 Speaker 1: Mars can during their larger orbits, so most of the time, 10 00:00:36,400 --> 00:00:40,000 Speaker 1: Mercury is closer to Earth than any other planet, despite 11 00:00:40,040 --> 00:00:43,239 Speaker 1: its place in the planetary lineup. And that's far from 12 00:00:43,240 --> 00:00:47,120 Speaker 1: the weirdest thing about Mercury's travel patterns. Of all the 13 00:00:47,120 --> 00:00:49,879 Speaker 1: planets in the Solar System, Mercury orbits our Sun at 14 00:00:49,880 --> 00:00:52,960 Speaker 1: the fastest rate. It zips around our star with an 15 00:00:52,960 --> 00:00:55,520 Speaker 1: average speed of around one hundred and five thousand, nine 16 00:00:55,600 --> 00:00:58,640 Speaker 1: hundred miles per hour or a hundred and seventy thousand, 17 00:00:58,640 --> 00:01:02,160 Speaker 1: five hundred kilometers per hour. The planet's namesake was a 18 00:01:02,200 --> 00:01:05,880 Speaker 1: real speedster too. In Roman mythology, Mercury was the fleet 19 00:01:05,880 --> 00:01:10,240 Speaker 1: footed god of commerce and communication, among other things. Recognizable 20 00:01:10,240 --> 00:01:14,039 Speaker 1: by his winged sandals. Earth takes a little more than 21 00:01:14,080 --> 00:01:16,559 Speaker 1: three hundred and sixty five days to loop around the sun. 22 00:01:17,240 --> 00:01:19,720 Speaker 1: Mercury does the same thing in a fraction of the time. 23 00:01:20,360 --> 00:01:23,440 Speaker 1: One Mercury in year is equal to a brisk eighty 24 00:01:23,480 --> 00:01:27,960 Speaker 1: eight earth days vacationing there would be a disorienting experience 25 00:01:29,000 --> 00:01:31,679 Speaker 1: on Mercury. The years may be quick, but the days 26 00:01:31,720 --> 00:01:35,399 Speaker 1: are very long. The planet finishes a new rotation around 27 00:01:35,440 --> 00:01:38,920 Speaker 1: its own axis once every fifty nine earth days, which 28 00:01:38,959 --> 00:01:42,200 Speaker 1: means that every day on Mercury takes up almost exactly 29 00:01:42,319 --> 00:01:46,800 Speaker 1: two thirds of every year. But due to some further strangeness, 30 00:01:46,840 --> 00:01:50,520 Speaker 1: each day on Mercury isn't guaranteed to have a sunrise 31 00:01:50,560 --> 00:01:54,240 Speaker 1: and a sunset. If we define a day not as 32 00:01:54,280 --> 00:01:57,080 Speaker 1: a complete rotation of a planet around its axis, but 33 00:01:57,240 --> 00:02:00,720 Speaker 1: rather as a solar day, a one complete day night cycle, 34 00:02:01,120 --> 00:02:03,120 Speaker 1: the amount of time it takes our son to return 35 00:02:03,200 --> 00:02:06,200 Speaker 1: to a specific point in the sky, then a single 36 00:02:06,360 --> 00:02:09,480 Speaker 1: day on Mercury is a hundred and seventy six earth 37 00:02:09,560 --> 00:02:13,320 Speaker 1: days long. That's the rough equivalent of two full Mercury 38 00:02:13,400 --> 00:02:17,200 Speaker 1: in years. That's because Mercury's orbit is what we refer 39 00:02:17,320 --> 00:02:21,840 Speaker 1: to as eccentric. No, not eccentric like Willy Wonka is eccentric. 40 00:02:22,240 --> 00:02:25,560 Speaker 1: Eccentricity is a term astronomers used to describe the shape 41 00:02:25,600 --> 00:02:29,120 Speaker 1: of a planet or moon's orbit. No planet orbits its 42 00:02:29,160 --> 00:02:31,880 Speaker 1: star in a perfect circle. The extent to which had 43 00:02:31,919 --> 00:02:36,240 Speaker 1: given orbit deviates from being circular is cold. It's eccentricity. 44 00:02:36,880 --> 00:02:39,720 Speaker 1: If an orbit was one circular, would say it had 45 00:02:39,760 --> 00:02:43,440 Speaker 1: an eccentricity of zero. Let The records show that Earth's 46 00:02:43,520 --> 00:02:48,239 Speaker 1: orbit boasts an eccentricity of just zero point zero one seven, 47 00:02:48,919 --> 00:02:53,760 Speaker 1: so it's almost a circle, but not quite. Mercury's orbit 48 00:02:53,800 --> 00:02:57,640 Speaker 1: looks more squashed or elliptical. By comparison of all the 49 00:02:57,680 --> 00:03:01,040 Speaker 1: planets in our beloved Solar system, Cury has the most 50 00:03:01,080 --> 00:03:04,560 Speaker 1: eccentric orbit. The amount of space between this world and 51 00:03:04,600 --> 00:03:07,760 Speaker 1: our Sun ranges from just twenty nine million miles to 52 00:03:07,880 --> 00:03:10,639 Speaker 1: thirty six million miles during the course of its elliptical 53 00:03:10,639 --> 00:03:13,520 Speaker 1: trip around the Sun. That's a forty six million to 54 00:03:13,639 --> 00:03:19,080 Speaker 1: fifty eight million kilometers. Consequently, Mercury's travel speed increases as 55 00:03:19,120 --> 00:03:22,120 Speaker 1: it gets closer to the star. Those changes in speed 56 00:03:22,160 --> 00:03:24,880 Speaker 1: and distance from the Sun account for the strange solar days. 57 00:03:25,520 --> 00:03:27,919 Speaker 1: When you view the Sun from some places on Mercury, 58 00:03:28,200 --> 00:03:30,720 Speaker 1: it appears to freeze in place part way through its 59 00:03:30,760 --> 00:03:34,560 Speaker 1: journey across the sky, then move backwards before going forward 60 00:03:34,560 --> 00:03:37,960 Speaker 1: again in its route to the opposite horizon. Depending on 61 00:03:38,000 --> 00:03:40,280 Speaker 1: where you are on the planet, this might mean that 62 00:03:40,320 --> 00:03:42,760 Speaker 1: you get to sunrises in a row as the Sun 63 00:03:42,840 --> 00:03:46,360 Speaker 1: dips back below the skyline before fully rising, or two 64 00:03:46,400 --> 00:03:48,960 Speaker 1: sunsets in a row as it pops back up before 65 00:03:49,000 --> 00:03:53,040 Speaker 1: fully setting, And of course all of this reeks havoc 66 00:03:53,120 --> 00:03:56,440 Speaker 1: on the planet's temperatures on Mercury, they can range as 67 00:03:56,520 --> 00:03:59,840 Speaker 1: high as eight hundred degrees fahrenheit that's four thirty celsius, 68 00:04:00,160 --> 00:04:03,120 Speaker 1: or as low as negative two nine degrees fahrenheit or 69 00:04:03,200 --> 00:04:06,760 Speaker 1: negative one eight celsius. As you could expect, the side 70 00:04:06,800 --> 00:04:08,840 Speaker 1: of the planet that's facing the Sun at any time 71 00:04:08,960 --> 00:04:12,880 Speaker 1: will be a good deal hotter, and on hot days 72 00:04:13,120 --> 00:04:17,680 Speaker 1: we could all use some ice in NASA's Messenger spacecraft 73 00:04:17,720 --> 00:04:21,240 Speaker 1: observed deposits of frozen water on Mercury. The ice was 74 00:04:21,240 --> 00:04:24,239 Speaker 1: found at the bottoms of deep craters around the northern pole, 75 00:04:24,520 --> 00:04:26,840 Speaker 1: which are protected from the sun all year long due 76 00:04:26,839 --> 00:04:29,720 Speaker 1: to Mercury's lack of tilt around its axis of rotation. 77 00:04:30,320 --> 00:04:33,279 Speaker 1: Earth tilts twenty three point five degrees on its axis, 78 00:04:33,320 --> 00:04:35,840 Speaker 1: giving us seasons and exposing the poles to the Sun. 79 00:04:36,400 --> 00:04:40,000 Speaker 1: But Mercury only tilts two degrees, meaning it spins almost 80 00:04:40,000 --> 00:04:44,000 Speaker 1: completely upright, protecting its poles and preventing seasons from occurring. 81 00:04:45,160 --> 00:04:49,719 Speaker 1: But back to that ice. Paradoxically, Mercury's hottest temperatures could 82 00:04:49,720 --> 00:04:52,159 Speaker 1: be responsible for some of the ice that it possesses. 83 00:04:52,920 --> 00:04:56,640 Speaker 1: Our Sun is constantly releasing charged protons and electrons in 84 00:04:56,760 --> 00:05:00,640 Speaker 1: streams known as solar winds. Earth is shielded by a 85 00:05:00,640 --> 00:05:04,880 Speaker 1: powerful magnetic field, which deflects many of these. Mercury has 86 00:05:04,880 --> 00:05:07,240 Speaker 1: had a magnetic field of its own four around three 87 00:05:07,240 --> 00:05:11,279 Speaker 1: point nine billion years. However, it's significantly weaker than the 88 00:05:11,279 --> 00:05:14,440 Speaker 1: one we enjoy here on Earth. If a recent scientific 89 00:05:14,480 --> 00:05:17,600 Speaker 1: model is correct, The intense heat of the planet's sun 90 00:05:17,640 --> 00:05:21,960 Speaker 1: facing side triggers chemical reactions between solar wind particles and 91 00:05:22,040 --> 00:05:25,719 Speaker 1: minerals buried in the soil. These are thought to create 92 00:05:25,800 --> 00:05:30,839 Speaker 1: traveling water molecules that later become ice. Of all the 93 00:05:30,880 --> 00:05:33,560 Speaker 1: frozen water on Mercury may have been generated this way, 94 00:05:35,440 --> 00:05:38,560 Speaker 1: Mercury doesn't have any moons to call its own. As 95 00:05:38,600 --> 00:05:40,960 Speaker 1: a matter of fact, With a diameter of just three thousand, 96 00:05:41,000 --> 00:05:45,480 Speaker 1: thirty miles or four thousand kilometers, Mercury isn't much bigger 97 00:05:45,520 --> 00:05:49,920 Speaker 1: than Earth's Moon easily. Mercury is the smallest planet in 98 00:05:49,960 --> 00:05:53,560 Speaker 1: our Sun's orbit, yet evidence tells us that it used 99 00:05:53,560 --> 00:05:57,080 Speaker 1: to be larger. Mercury is interesting to look at from 100 00:05:57,080 --> 00:06:00,680 Speaker 1: a topographic standpoint. The thin atmosphere for his very little 101 00:06:00,720 --> 00:06:05,120 Speaker 1: protection from asteroids, so impact craters are abundant. A single 102 00:06:05,160 --> 00:06:07,640 Speaker 1: photo taken by the Messenger Probe in two thousand eight 103 00:06:07,839 --> 00:06:11,440 Speaker 1: shows seven hundred and sixty three identifiable craters within a 104 00:06:11,520 --> 00:06:13,680 Speaker 1: region of the planet's surface just a hundred and seventy 105 00:06:13,680 --> 00:06:16,600 Speaker 1: two miles wide. That's two hundred and seventy six kilometers. 106 00:06:17,839 --> 00:06:20,720 Speaker 1: It's traditional to name these craters after writers, given that 107 00:06:20,880 --> 00:06:24,440 Speaker 1: eloquence is one of the realms of the mythological god Mercury. 108 00:06:24,600 --> 00:06:28,559 Speaker 1: Truman Capote, Batteline la Engel, Betty Alver, and John Lennon 109 00:06:28,680 --> 00:06:31,640 Speaker 1: are just some of the visionaries with their own namesake craters. 110 00:06:33,080 --> 00:06:36,480 Speaker 1: The planet's face is also marked by fault scarps. These 111 00:06:36,520 --> 00:06:39,040 Speaker 1: are cliff ridges that were first sighted on Mercury in 112 00:06:39,040 --> 00:06:42,040 Speaker 1: the nineteen seventies. Some of the smaller ones appeared to 113 00:06:42,080 --> 00:06:45,520 Speaker 1: be around just fifty million years old, making them geologically 114 00:06:45,640 --> 00:06:50,000 Speaker 1: pretty young. Mercury itself formed around four point five billion 115 00:06:50,080 --> 00:06:53,520 Speaker 1: years ago. Since then, its metallic core has been cooling 116 00:06:53,600 --> 00:06:56,880 Speaker 1: down at a rapid pace, and as a result, the 117 00:06:56,960 --> 00:07:01,120 Speaker 1: whole planet is currently shrinking. The diameter of mercury may 118 00:07:01,160 --> 00:07:03,000 Speaker 1: have contracted by as much as eight and a half 119 00:07:03,080 --> 00:07:06,560 Speaker 1: miles or fourteen kilometers over the eons. This has had 120 00:07:06,600 --> 00:07:10,160 Speaker 1: a tremendous effect on the planet's rocky outer surface. Those 121 00:07:10,280 --> 00:07:13,880 Speaker 1: previously mentioned fault scarps are born when crust materials break 122 00:07:13,960 --> 00:07:17,320 Speaker 1: apart and press into each other, forcing some terrain upward. 123 00:07:18,320 --> 00:07:22,400 Speaker 1: And because it's tectonically active in its own peculiar way, Mercury, 124 00:07:22,760 --> 00:07:27,680 Speaker 1: like Earth, may experience surface level earthquakes. Mercury quakes will 125 00:07:27,680 --> 00:07:30,520 Speaker 1: definitely be a topic worth investigating as we plot out 126 00:07:30,560 --> 00:07:38,960 Speaker 1: future pro missions to our curious little neighbor. Today's episode 127 00:07:39,000 --> 00:07:41,720 Speaker 1: was written by Mark Mancini and produced by Tyler clang Or. 128 00:07:41,800 --> 00:07:43,800 Speaker 1: More on this and lots of other curious topics, visit 129 00:07:43,840 --> 00:07:46,400 Speaker 1: how stuff works dot com. Brain Stuff is production of 130 00:07:46,440 --> 00:07:49,200 Speaker 1: Iyheart Radio. Or more podcasts my heart Radio, visit the 131 00:07:49,240 --> 00:07:52,000 Speaker 1: iHeart Radio app. Apple podcasts, or wherever you listen to 132 00:07:52,080 --> 00:07:52,840 Speaker 1: your favorite shows.