Space & Astronomy

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Jupiter is not just the biggest planet — it is more than twice as massive as all the other planets combined, and about 11 Earths could line up across its face. Its Great Red Spot is a single storm wider than our entire planet. Saturn is a tempting pick because its rings make it look the grandest, but it is the runner-up in size and far lighter. Neptune and Uranus are giants too, yet each is only about four Earths wide — impressive, but a different league entirely.

Source: NASA Science: Jupiter facts (science.nasa.gov/jupiter/jupiter-facts/)

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Sunlight crosses the 150 million kilometres (93 million miles) to Earth in about 8 minutes and 20 seconds — so every sunbeam you see left the Sun before you looked up, and we always see the Sun as it was 8.3 minutes ago. Instant arrival feels right because light seems immediate in daily life, but even at 300,000 km per second the gulf of space takes time to cross. Eight seconds hugely underestimates that distance, while eight hours overshoots it — light needs only about five and a half hours to reach even distant Pluto.

Source: NASA Science: Sun facts (science.nasa.gov/sun/facts/)

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Venus holds the record at about 465 degrees Celsius (870 degrees Fahrenheit) — hot enough to melt lead — because its crushing carbon dioxide atmosphere traps heat in a runaway greenhouse effect. Mercury is the tempting answer since it orbits closest to the Sun, but with almost no atmosphere to hold warmth, its heat escapes and its night side plunges hundreds of degrees below freezing. Mars looks fiery red yet is actually a frigid desert averaging well below zero, and Jupiter's swirling cloud tops are colder still, far out in the dim outer solar system.

Source: NASA Science: Venus facts (science.nasa.gov/venus/venus-facts/)

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Ganymede, orbiting Jupiter, spans about 5,260 kilometres — making it larger than the planet Mercury. It is also the only moon known to generate its own magnetic field, and evidence points to a buried saltwater ocean holding more water than all of Earth's surface oceans. Saturn's Titan is the classic near-miss: it is the second largest and famous for its thick atmosphere, so it often steals the credit. Earth's Moon feels enormous in our sky but ranks only fifth, and Europa, though fascinating for its hidden ocean, is smaller than our Moon.

Source: NASA Science: Ganymede facts (science.nasa.gov/jupiter/jupiter-moons/ganymede/facts/)

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Soviet cosmonaut Yuri Gagarin became the first human in space on 12 April 1961, circling Earth once aboard Vostok 1 in a flight lasting just 108 minutes — and he parachuted separately from his capsule before it hit the ground. Neil Armstrong is the tempting mix-up because he was the first person to walk on the Moon, but that came eight years later, in 1969. Alan Shepard became the first American in space only weeks after Gagarin, on a short suborbital hop, and John Glenn was the first American to actually orbit Earth, in 1962.

Source: NASA: First Human Entered Space, April 1961 (nasa.gov/image-article/april-1961-first-human-entered-space/)

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Venus needs 243 Earth days to complete a single rotation but only 225 Earth days to finish a lap around the Sun — its 'day' genuinely outlasts its year. Stranger still, it spins backwards compared with most planets, so from its surface the Sun would rise in the west. Mercury is the tempting near-miss: it is a famously sluggish spinner, yet its 59-day rotation still comfortably beats its 88-day year. Mars is nearly Earth's twin in day length at about 24.6 hours, and Neptune whips around on its axis in roughly 16 hours despite its 165-year orbit.

Source: NASA Science: Venus facts (science.nasa.gov/venus/venus-facts/)

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Olympus Mons towers about 25 kilometres above the surface of Mars — roughly three times the height of Mount Everest — with a base the size of Arizona. It grew so monstrous because Mars lacks moving tectonic plates: lava kept erupting over the same hotspot for ages, piling ever higher instead of forming a chain of smaller volcanoes as happens on Earth. Io is a clever-sounding trap since it is the most volcanically active body in the solar system, but its eruptions build no giant like this. Venus is dotted with volcanoes too, and Earth's biggest, Mauna Loa, is a fraction of the size.

Source: ESA: Olympus Mons, 25 kilometres high (esa.int) and NASA APOD 2023-04-04: Olympus Mons

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The Sun accounts for about 99.8 percent of the solar system's entire mass — every planet, moon, asteroid, and comet together makes up the remaining sliver, and Jupiter claims most of that. The Sun's interior could swallow more than 1.3 million Earths. Guesses like half or three-quarters feel reasonable because the planets seem so substantial, especially giant Jupiter, yet even Jupiter carries only about a thousandth of the Sun's mass. Even the cautious-sounding 90 percent wildly overrates the planets: in mass terms, the solar system is essentially the Sun plus rounding error.

Source: NASA Science: Solar System facts (science.nasa.gov/solar-system/solar-system-facts/)

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The Moon spins on its axis in the same 27.3 days it takes to orbit Earth, a state called synchronous rotation caused by tidal locking — Earth's gravity gradually braked the Moon's spin until the two motions matched. The idea that the Moon does not rotate is the classic trap: if it truly never turned, we would see every side of it over a month. Calling the far side 'permanently dark' repeats another myth — it receives just as much sunlight as the near side, only during our lunar night. Earth's shadow, meanwhile, touches the Moon only during brief lunar eclipses.

Source: NASA Science: Tidal Locking (science.nasa.gov/moon/tidal-locking/)

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Saturn is the only planet in the solar system less dense than water — its average density is about 70 percent that of water — because it is a vast, puffed-up ball of the two lightest elements, hydrogen and helium. Jupiter is the tempting choice since it is made of much the same gases, but its colossal mass squeezes its interior so hard that it ends up denser than water and would sink. Uranus and Neptune sound plausible as gassy outer worlds too, yet they are 'ice giants' rich in heavier water, ammonia, and methane, making both comfortably denser than water.

Source: NASA Science: Saturn facts (science.nasa.gov/saturn/facts/) and Britannica: Saturn

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A neutron star is what's left after a massive star's core collapses in a supernova, crushing protons and electrons together into neutrons until gravity overwhelms every other force holding ordinary matter apart. The result packs roughly 1.4 times the Sun's mass into a sphere only about 20 kilometres wide, giving densities around 10^17 kg per cubic metre -- so a teaspoon-sized sample would weigh in the neighbourhood of a billion tons, more than the combined weight of every person alive on Earth squeezed into a space smaller than a sugar cube. Guessing a single ton badly underestimates the compression by nine orders of magnitude, since normal matter (even something as dense as a car's steel) is nowhere near this collapsed state. A thousand tons and a million tons both fall short too, by six and three orders of magnitude respectively -- appealingly large numbers, but still nowhere close to capturing just how extreme neutron-degenerate matter really is.

Source: NASA Goddard, Imagine the Universe: 'Neutron Stars' (imagine.gsfc.nasa.gov); NASA HEASARC compact-objects overview

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Real asteroids in the main belt are typically several hundred thousand kilometres apart from their nearest neighbour, and the belt's combined mass -- despite containing millions of individual rocks -- adds up to only around 4% of the Moon's mass, with more than 60% of that total concentrated in just four objects (Ceres, Vesta, Pallas, and Hygiea). That vast emptiness is exactly why the chance of a spacecraft accidentally hitting an asteroid while crossing the belt is estimated at less than one in a billion, nothing like the tightly packed rubble fields Hollywood loves to show. The option describing asteroids only a few hundred metres apart, and the one describing a mere few kilometres of separation, both wildly overstate the belt's crowding by many orders of magnitude. The option claiming the belt holds almost no solid bodies larger than a car is wrong for the opposite reason: Ceres alone, the belt's largest resident and a recognised dwarf planet, is roughly 940 kilometres across.

Source: NASA Science: 'Asteroid Facts' (science.nasa.gov/solar-system/asteroids/facts); NASA JPL asteroid belt density estimates

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The Great Red Spot is a giant anticyclonic storm swirling in Jupiter's upper atmosphere, not a feature of any solid surface -- Jupiter is a gas giant with no rocky surface to crater or erupt from in the first place. Continuous observations date back to 1878, and it may be the same 'Permanent Spot' Giovanni Cassini recorded as early as 1665, making it one of the longest-lived storms known anywhere in the solar system. Even though it has shrunk by roughly half over the past century and continues contracting today, recent Hubble measurements still put it at around 10,250 miles across -- wider than Earth's roughly 7,918-mile diameter. The impact-crater and volcanic-caldera options are both wrong because Jupiter has no solid crust for a crater to scar or a caldera to form on. The ring-reflection option is wrong too: Jupiter's rings are extremely faint and dusty, nothing like a mirror, and completely unrelated to the storm's reddish colouring, which instead comes from chemical compounds churned up from deeper in the atmosphere.

Source: NASA Science: 'NASA's Hubble Shows Jupiter's Great Red Spot Is Smaller than Ever Measured' (science.nasa.gov); Britannica: 'Great Red Spot'

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The IAU's 2006 definition requires a planet to (a) orbit the Sun, (b) have enough self-gravity to pull itself into a round, hydrostatic-equilibrium shape, and (c) have cleared its orbital neighbourhood of other comparably sized objects. Pluto satisfies the first two criteria without dispute -- New Horizons confirmed it is genuinely round -- but fails the third: it shares its orbital region with countless other Kuiper Belt objects of significant size, rather than gravitationally dominating and sweeping that zone clear the way the eight recognised planets do. The option claiming Pluto orbits Neptune instead of the Sun is wrong; Pluto independently orbits the Sun, even though its orbit is in resonance with Neptune's. The option claiming Pluto isn't round is wrong, since its own gravity has pulled it into hydrostatic equilibrium, satisfying that criterion. The option about composition is wrong because the IAU's definition says nothing at all about whether a planet must be rocky rather than icy -- several recognised planets, including Jupiter and Saturn, aren't rocky either.

Source: IAU Resolution B5 (2006), 'Definition of a Planet in the Solar System'; Library of Congress: 'Why is Pluto no longer a planet?'

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The Moon has no atmosphere at all, which means no wind, rain, or flowing water ever reaches its surface to disturb loose soil the way weather does on Earth. Without any of that erosion, the only forces still acting on the footprints are extremely slow ones -- the occasional micrometeorite impact and repeated heating-and-cooling cycles -- meaning most of the bootprints left by Apollo astronauts should remain visible for millions of years, as suggested by Lunar Reconnaissance Orbiter imagery and by repeat photographs of the Apollo 12 site taken 31 months apart, which found almost no detectable change. Moonquakes do occur, but they are far too weak and infrequent to flatten fine surface impressions within mere decades. Oxidation isn't a meaningful factor either, since the Moon has essentially no atmospheric oxygen to react with the soil. And while sunlight does subject the dust to thermal stress over time, that process works so slowly that it could never erase these marks within just a few years.

Source: NASA Lunar Reconnaissance Orbiter Camera imagery of Apollo landing sites (nasa.gov); Space.com: 'Eugene Cernan's Legacy: Apollo 17 Commander's Footprints Still on the Moon'

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The ISS orbits about 400 kilometres up, low enough that it must move very fast -- around 28,000 km/h (about 17,500 mph) -- just to keep falling around Earth rather than down onto it, completing a full lap roughly every 90 minutes. That works out to about 16 orbits every 24 hours, which is also why astronauts on board experience roughly 16 sunrises and sunsets in a single day. The option describing a 24-hour orbital period describes a geostationary satellite instead, which sits roughly 36,000 kilometres up -- nearly 90 times higher than the ISS -- precisely so its orbital period matches Earth's rotation; the ISS's much lower orbit demands a much faster lap time, not a matching one. The option citing a 6-hour, 5,000 km/h orbit understates the station's real speed and orbital frequency by a wide margin. The option citing 40,000 km/h is roughly Earth's escape velocity, the speed needed to leave orbit entirely -- far faster than the ISS travels, since it needs to stay bound to Earth, not escape it.

Source: NASA: 'International Space Station Facts and Figures' (nasa.gov/international-space-station/space-station-facts-and-figures)

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Common sense says temperature should keep dropping as you move further from the Sun's fusion-powered core, and that's exactly what happens up through the visible photosphere, at around 5,500 degrees Celsius. But the wispy corona above it, visible to the naked eye only during a total eclipse, somehow reaches temperatures of one to three million degrees Celsius -- hundreds of times hotter than the surface directly beneath it. This reversal defies simple physics and has puzzled scientists since the 19th century as the 'coronal heating problem,' with leading explanations today involving magnetic Alfven waves and small explosive 'nanoflares' carrying energy upward. The option claiming the corona is nearly absolute zero gets the direction of the mystery backwards -- it's dramatically hot, not cold. The option claiming it matches the photosphere's temperature misses the entire puzzle, since the striking fact is exactly how different the two temperatures are. The option describing the corona as merely varying with the solar cycle while staying cooler by design misrepresents an open scientific mystery as a settled, intentional feature, which it is not.

Source: NASA Space Place: 'What Is the Sun's Corona?' (spaceplace.nasa.gov/sun-corona); NASA IRIS mission coronal-heating findings

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Saturn's rings are made of countless individual particles of ice and rock, each independently orbiting the planet in an extremely flat plane, which is why the entire ring system can stretch roughly 270,000 kilometres across while measuring less than 100 metres thick in most places -- no taller than a couple of stacked city buildings. That ratio is so extreme that if Saturn were shrunk to the size of a basketball, its rings would end up thinner than a sheet of paper. The three larger options -- 50,000 km, 10,000 km, and 3,000 km -- all describe a system many thousands to tens of thousands of times thicker than the rings actually are, more in line with the scale of a planet or a large moon than with a wafer-thin band of orbiting debris. None of them capture just how astonishingly flat this structure really is relative to its enormous width.

Source: NASA Science: 'Pencil-thin Rings' (science.nasa.gov/resource/pencil-thin-rings); Britannica: Saturn -- The ring system

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Betelgeuse is a red supergiant roughly 700 times the Sun's radius, so large that if it took the Sun's place, its outer atmosphere would immediately swallow Mercury, Venus, Earth, and Mars -- the entire inner rocky solar system -- and, depending on exactly where it sits in its pulsation cycle, could swell out to nearly Jupiter's orbit. The option claiming red supergiants are smaller than the Sun has the basic astrophysics backwards: 'supergiant' describes some of the largest stars known, far bigger than the Sun, not smaller. The option stopping the swallowing at Venus, leaving Earth untouched, understates the star's reach, since a star already large enough to engulf Venus's orbit necessarily engulfs Earth's smaller orbit too. The option extending the destruction all the way out to Neptune overshoots badly: even at its most swollen, Betelgeuse's reach falls well short of Neptune's orbit some 30 times farther from the Sun than Earth, only approaching the much closer orbit of Jupiter.

Source: NASA Science: 'What Is Betelgeuse? Inside the Strange, Volatile Star' (science.nasa.gov/universe/what-is-betelgeuse-inside-the-strange-volatile-star); Britannica: 'Betelgeuse'

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While Armstrong and Aldrin descended to the surface in the lunar module Eagle, Michael Collins remained alone aboard the command module Columbia, orbiting the Moon for around 28 hours and losing all contact with Mission Control and his crewmates every time his orbit carried him behind the Moon's far side, cut off from any radio signal. He also stood ready to fly a rescue manoeuvre if Eagle had failed to make it back into lunar orbit. He was never on Earth during this period, ruling out the option placing him at Mission Control in Houston. There was only a single lunar module on the mission, so the option describing a second lander touching down nearby describes a spacecraft that never existed. And Collins never set foot on the lunar surface at all -- that option confuses his role entirely, since his job was to stay in orbit above, not join the moonwalk below.

Source: NASA: Apollo 11 mission overview (nasa.gov); Space.com: 'Michael Collins, Apollo 11 Command Module Pilot'

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Jupiter spins once on its axis in roughly 9 hours and 56 minutes at its higher latitudes (about 9 hours 50 minutes at the equator), the shortest day of any planet, even though it is more than eleven times Earth's diameter. That spin carries Jupiter's equator around at roughly 28,000 miles per hour (about 45,300 km/h), more than 27 times Earth's equatorial speed, and the resulting outward bulge flattens the planet into a visibly oblate shape rather than a perfect sphere. Saturn is the tempting runner-up, another fast-spinning gas giant, but its day is slightly longer at about 10 hours 33 minutes. Neptune and Uranus are gas and ice giants too, yet both take noticeably longer to complete a rotation, roughly 16 hours and 17 hours respectively, placing them well behind the two fastest spinners rather than ahead of them.

Source: NASA Science: Jupiter facts (science.nasa.gov/jupiter/jupiter-facts/); NASA NSSDCA Planetary Fact Sheets

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Saturn's moon Titan is the only place besides Earth known to have standing liquid, in the form of rivers, lakes, and seas, actually resting on its surface, complete with clouds and rain in a genuine weather cycle. Because Titan's surface temperature hovers around minus 179 degrees Celsius, water is frozen solid as rock-hard ice, so the liquid filling its lakes and seas is instead methane and ethane, hydrocarbons that stay liquid at those frigid temperatures. Europa and Enceladus are the tempting near-misses: both are icy moons with strong evidence of vast liquid-water oceans, but those oceans sit buried beneath many kilometers of ice crust, not exposed on the surface. Mars shows ample evidence of ancient rivers and lakebeds, yet its current atmosphere is far too thin and cold for liquid to persist openly on the surface today, so it has no standing surface liquid of its own.

Source: NASA Science: Titan facts (science.nasa.gov/saturn/moons/titan/facts/); NASA JPL: 'NASA Confirms Liquid Lake on Saturn Moon'

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A meteor is the streak of light produced when a small chunk of rock or dust, called a meteoroid while still travelling through space, slams into Earth's atmosphere at tremendous speed and burns up from friction with the air, giving the 'shooting star' its glow; despite the nickname, it was never a star at all. The option naming the surviving rock as the answer describes a meteorite instead, which is specifically the name given to any fragment that survives the fiery trip and actually lands on the ground, a rarer outcome than simply burning up completely. The option naming a large rocky body describes an asteroid, a chunk of rock, sometimes hundreds of kilometres across, that stays in orbit around the Sun rather than a brief atmospheric flash. The option naming an icy body describes a comet, a mass of ice and dust that can grow a glowing tail as it nears the Sun, an entirely different object with a different composition and orbital behaviour.

Source: NASA: 'What's the Difference Between Asteroids, Comets and Meteors? We Asked a NASA Scientist' (nasa.gov/directorates/smd/); Smithsonian National Air and Space Museum: 'What is the difference between asteroids, comets and meteors?'

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On Earth, sunsets turn red and orange because the thick atmosphere scatters shorter blue wavelengths away in every direction over the long, low-angle path sunlight travels at dusk, leaving mostly red and orange light heading straight at an observer's eyes. On Mars, Curiosity's images of twilight show the opposite effect: the atmosphere is far too thin for that same kind of scattering, but it carries abundant fine dust, and particles of just the right size scatter blue light efficiently in the forward direction, concentrating a blue glow in a halo right around the Sun while the surrounding sky, dominated by dust scattering other wavelengths, stays yellow to orange. The option invoking methane is wrong because trace methane exists only in minute, variable concentrations and plays no documented role in Martian sky color. The option claiming Mars matches Earth's reddish sunsets is wrong because the two planets' atmospheres and dominant scattering mechanisms differ sharply, producing near-opposite results. The option claiming Mars has no suspended dust is wrong because dust, including dust lofted by Mars's famous planet-wide dust storms, is precisely the ingredient that produces the blue sunset glow in the first place.

Source: NASA JPL: 'NASA's Curiosity Rover Views Serene Sundown on Mars' (jpl.nasa.gov)

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Space itself is close to a perfect vacuum, with essentially no molecules present to carry any odor, so nobody actually smells 'space' directly; the smell astronauts describe, often as hot metal, seared steak, or spent gunpowder, only appears once they come back inside and take off their gear. NASA attributes it to reactive residue picked up during the spacewalk: polycyclic aromatic hydrocarbons, sturdy ring-shaped molecules common throughout the universe and found in substances like soot, along with oxidation from atomic oxygen and ozone encountered in low Earth orbit, both cling to the suit's helmet, gloves, and tools, then react with the cabin's air once the astronaut is back inside, producing the sharp metallic odor. The rocket-exhaust option is wrong because a spacewalking astronaut's suit and the station's life-support system are entirely separate from any engine, with no exhaust pathway into the cabin. The breath-condensation option is wrong because moisture from breathing would produce a humid or faintly organic smell, not the specific metallic, seared odor astronauts consistently report. The suit-cooling-system option is wrong because NASA's own explanation centers on exterior surface residue picked up in orbit, not on the suit's internal cooling hardware degassing.

Source: NASA: 'Interesting Fact of the Month' (nasa.gov/?p=481946), astronaut quotes from Greg Chamitoff and Don Pettit; Science.org coverage of the same phenomenon

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Valentina Tereshkova became the first woman in space when she launched aboard Vostok 6 from the Baikonur Cosmodrome on 16 June 1963, orbiting Earth 48 times over roughly three days before parachuting back to the ground, having been selected from a pool of candidates partly for her civilian parachuting experience. The option naming the first American woman in space is a tempting near-miss because she is the most famous woman astronaut in the West, but she did not fly until 1983, two decades after Tereshkova's flight, aboard the Space Shuttle rather than a Soviet capsule. The option naming the first African American woman in space refers to a flight that took place even later, in 1992, aboard the Space Shuttle, and is a distinct historical first rather than the first woman overall. The option naming the cosmonaut who became the first woman to perform a spacewalk refers to an achievement from 1984, over two decades after Tereshkova and more than a year after the American woman's flight, making her a 'first' for a specific activity, not for spaceflight itself.

Source: Encyclopaedia Britannica: 'Valentina Tereshkova'; NASA astronaut biography pages for Sally Ride and Mae Jemison (nasa.gov); Encyclopaedia Britannica: 'Svetlana Savitskaya'

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A comet's tail is driven by the Sun itself: sunlight ionises gas boiling off the comet's icy surface, and the outward-streaming solar wind sweeps those ions straight away from the Sun, while solar radiation pressure pushes the dust that forms the second, broader tail in roughly the same outward direction. Because both forces always point away from the Sun, the tail always points away from the Sun too, no matter which way the comet itself happens to be moving at that moment. This produces a genuinely strange result once a comet has passed the Sun and is heading back out into deep space: its tail now points ahead of it, since 'away from the Sun' and 'direction of travel' are no longer the same thing. The option describing a wake trailing behind the comet's path matches everyday intuition from boats and aircraft, but fails this exact outbound scenario. The option describing the tail being pulled toward the Sun has the direction backward: the comet's icy nucleus is pulled toward the Sun by gravity, but the escaping gas and dust that form the tail are pushed away from it. The option describing a single fixed direction in space ignores that the tail's direction constantly re-orients itself to keep pointing away from the Sun's current position as the comet moves along its orbit.

Source: NASA Science: 'Comets' overview (science.nasa.gov/solar-system/comets/); NASA Astronomy Picture of the Day description of Comet McNaught's solar-radiation-pressure-driven dust tail (science.nasa.gov)

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Phobos and Deimos are tiny by planetary standards, only about 22 and 12 kilometres across, far too small for their own gravity to pull them into a round shape, which is why both are lumpy and irregular rather than spherical. The leading explanation for their origin is that they are asteroids that formed elsewhere in the solar system, most likely in the main asteroid belt between Mars and Jupiter, and were later captured into orbit by Mars's gravity; recent close flyby data showing that the two moons are made of noticeably different rocky material has strengthened this capture theory, since a single shared origin would be expected to leave them more similar. The option describing large, round moons like Earth's is wrong on both size and shape: Phobos and Deimos are minuscule and potato-shaped, nothing like Earth's single large sphere. The option describing icy, smooth moons is wrong because both are rocky, heavily cratered bodies, not ice-covered worlds like the large moons found around the outer gas giants. The option describing debris from a giant impact on Mars itself names a real, genuinely competing scientific hypothesis, similar to how Earth's own Moon is thought to have formed, but current evidence, including the moons' differing compositions, is considered to favour the capture theory over this impact-debris idea.

Source: NASA Science: 'Phobos' and 'Deimos' Mars moon facts (science.nasa.gov/mars/moons/); NASA: 'Doomed Moon of Mars' feature on flyby composition findings supporting the capture theory (nasa.gov)

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The International Space Station orbits roughly 400 kilometres above Earth, where Earth's gravity is still about 90 percent as strong as it is at the surface, so gravity has not disappeared at all; what has changed is that the station is moving sideways at around 28,000 kilometres per hour. At that speed, the station and everything inside it are falling toward Earth continuously, but Earth's surface curves away beneath them at almost exactly the same rate that they fall, so they keep 'missing' the ground forever. That permanent, matched fall is what an orbit actually is, and because the astronauts, the station, and every loose object inside it are all falling at the same rate together, nothing presses against anything else, which is what produces the floating sensation, properly called apparent weightlessness rather than true zero gravity. The option claiming gravity does not reach that far is wrong given how strong gravity still is at that altitude. The option describing a spin-induced centrifugal cancellation describes a proposed design for possible future rotating space stations, not how the current, non-spinning International Space Station actually works. The option blaming the vacuum's lack of air resistance confuses two unrelated things: air resistance affects falling speed within an atmosphere, but weightlessness in orbit would occur even with an atmosphere present, since it is purely a consequence of continuous free fall.

Source: NASA: 'What Is Microgravity?' student explainer (nasa.gov); NASA International Space Station facts on orbital altitude and velocity (nasa.gov/mission/international-space-station)

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Earth completes a lap of the Sun in about 365 days, while Mars, on a larger orbit, takes roughly 687 days, so Earth is always moving faster and periodically catches up to and overtakes Mars, about once every 26 months, much like a faster car passing a slower one on a curving track. During that overtaking window, the angle from which Earth-based observers view Mars against the distant background stars shifts rapidly, and that shifting vantage point, not any real change in Mars's own motion, is what makes Mars appear to slow, stop, and loop backward for several weeks before resuming its usual forward path. This apparent-motion puzzle, called retrograde motion, badly confused astronomers for centuries before the geometry of the two planets' relative orbital speeds explained it, and it still occurs for every planet beyond Earth's orbit, not just Mars. The option claiming Mars genuinely reverses its orbital direction is wrong: no planet actually travels backward along its orbit, even though orbital speed does vary somewhat depending on distance from the Sun. The option blaming Jupiter's gravity is wrong because Jupiter's pull perturbs Mars's orbit only very slightly over long timescales and cannot produce a regular, weeks-long backward loop every 26 months. The option blaming Earth's atmosphere bending light is wrong because atmospheric refraction only shifts an object's apparent position slightly near the horizon and cannot produce a sustained backward loop across a large swath of sky.

Source: NASA Science: Astronomy Picture of the Day explanation of Mars retrograde motion (science.nasa.gov); Live Science: 'Mars Retrograde Motion Explained'