This was an observation that cried out for an explanation, and so we began contrasting the two innermost planets. A day on Mercury lasts 59 Earth days. This is the great advantage of Mercury, which encounters nearly four times the flux per square meter compared to Venus. And yet, Venus is still hotter, which tells us that something else important must be going on with one of the other two points. Image credit: Wikimedia Commons user Jonathan Chone, under a c.c.a.-s.a.-4.0 international license, modified by E. Siegel. As far as absorbing and radiating heat goes, it turns out that size doesn’t matter very much. This difference is completely irrelevant. Mercury is visible to the naked eye. If it weren’t for Earth’s atmosphere, the mean temperature on our planet would be a paltry 255 Kelvin (-18 °C / -1 °F), or approximately the temperature of the Antarctic continent. With a diameter of 12,014 kilometers (7,465 miles), Venus is only slightly smaller than our planet. Image credit: NASA / JPL-Caltech / R. Hurt, modified by E.... [+] Siegel. Smallest. Can We Outrun Dark Energy In The Race To See The Universe? The first reason is of course due to the lack of an atmosphere within Mercury and the second reason is due to the differences on both planets absorption and reflective rates. “There is no question that climate change is happening; the only arguable point is what part humans are playing in it.” –David Attenborough. The blanket-like effect of the clouds and atmospheric gases lift our planet's climate into the temperate zone where life-as-we-know it has thrived for so long. Image credit: ESA/IPEV/PNRA–B. You see, Mercury and Venus don’t just absorb light from the Sun; each planet then re-radiates that energy as heat back into space. Why Mercury isn’t the Solar System’s hottest planet. As the light from the Sun spreads out through space, a more distant world intercepts less and less of its energy. But if a planet’s various orbital parameters were the only things that determined temperature, then the closest planet to the Sun would inevitably be the hottest, and they would all get progressively cooler as we moved farther and farther away. The long nights provide no escape from the heat, as the trapping and thermalizing effects of the cloud layers keep the surface of Venus at an inhospitably high temperature, so much so that if you added up the operational time of every lander that ever touched down on Venus’ surface, it wouldn’t even sum to half an Earth-day. Mercury has been known to humanity since ancient times and although its discovery date is unknown, the first mentions of the planet are believed to be around 3000 BC by the Sumerians. The Universe is out there, waiting for you to discover it. It's up to humanity to learn those lessons and decide what we do next. Mercury is the only terrestrial planet that still has hydrogen and helium in its atmosphere. The lower an object’s albedo is, the better it is at absorbing light, which means the higher the albedo, the less sunlight actually gets absorbed. If Earth were the size of a nickel, Mercury would be about as big as a blueberry. approximately -20 Celsius. You see, Mercury and Venus don’t just absorb light from the Sun; each planet then re-radiates that energy as heat back into space. Why could Mars not hold onto its atmosphere? Mercury is the smallest and innermost planet in the Solar System.Its orbit around the Sun takes 87.97 Earth days, the shortest of all the planets in the Solar System. In fact, even though Mercury is, by far, the planet that is most exposed to the Sun’s radiation, because of its (practical lack of) atmosphere it doesn’t keep much of its warm. While Earth isn't at risk of the same fate, Venus stands as both the hottest world in our Solar System and a cautionary tale of an out-of-control greenhouse effect. The long nights provide no escape from the heat, as the trapping and thermalizing effects of the cloud layers keep the surface of Venus at an inhospitably high temperature, so much so that if you added up the operational time of every lander that ever touched down on Venus' surface, it wouldn't even sum to half an Earth-day. To an excellent approximation, the Sun keeps not only Earth, but all the planets at a temperature well above what they'd be without it: just a few Kelvin. This was an observation that cried out for an explanation, and so we began contrasting the two innermost planets. Mercury is the smallest of the eight planets and is closest to the sun. That’s just embarrassing. Why isn’t Mercury the Hottest Planet? Note how Venus' atmosphere... [+] diffracts sunlight around it, while Mercury's lack of atmosphere shows no such effects. And yet, when you measure the temperature of Venus, there’s a surprise: Venus is the same temperature at all times, day or night, at an average of 735 Kelvin (462 °C / 863 °F), making it even hotter than Mercury! Each quantum of infrared radiation — the re-radiated heat — has got to get through that thick, thick atmosphere, which is difficult. This sulfuric acid haze, which extends for more than 20 km in thickness, encircles the planet at speeds from 210 to 370 km/hr, trapping the vast majority of the radiated heat and transferring it all across the planet. The Moon’s average albedo is only about 0.12, which means only 12% of the light that hits it get reflected, while the other 88% gets absorbed. Perhaps a gas giant that was large enough to generate a significant fraction of its own heat would change that order (if Jupiter and Neptune were swapped, this might be the case), but in general we’d expect a planet’s temperature to drop in proportion to its distance from the Sun. Its also believed to have a central iron core and a rocky mantle (much … With a radius of 1,516 miles (2,440 kilometers), Mercury is a little more than 1/3 the width of Earth. It also rotates even slower than Mercury, spending more than 100 consecutive Earth-days at a time bathed in sunlight and then an equal amount of time in darkness. The fact that Venus is nearly twice as far from the Sun, however, matters a great deal. Mercury is the closest planet to the sun. Earth? We also expect seasons — cool times and warm times — based on both how elliptical a planet’s orbit is and on its axial tilt. Image credit: Wikimedia Commons user Jonathan Chone, under a c.c.a.-s.a.-4.0 international license, modified by E. Siegel. And less of its energy you ad-free by our Patreon supporters Chone, under c.c.-by-s.a. Albedo between 0 and 1 Earth 's Moon is actually quite easy to explain than any known naturally temperatures! 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why mercury is not the hottest planet

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