Why Now?
Earth and Mars range in distances to each other dramatically, from ~401 million km to ~56 million km (over 7 fold difference), the shortest ride (taking ~7 months now) happening only once every 2 years. This short distance means less fuel and less money spent [1].
However, during this long 7 month travel, the planets are still moving, meaning that, in order to get to Mars in the shortest time, rockets must use the ‘Hohmann Transfer Orbit’ (a specific trajectory to get to Mars). This means there’s a specific time that rockets have to take off from Earth to get to Mars in that short time, but also at the right angle to approach either the orbit of Mars or the Martian surface [2].
Hohmann transfer orbit (1 = Earth, 2 = transfer orbit, 3 = Mars). Credit: Waterced
Why Mars?
It’s a captivating salmon pink object in the sky which has inspired human kind’s imagination to think aliens built canals on Mars, and also led H. G. Wells to write “The War of the Worlds” characterising the life forms on Mars as evil [21][22].
As well as this, a Martian day is very similar to an Earth day (40 minutes longer than on Earth), and it has a similar surface area to Earth’s continents, all making it easier for humans to acclimatise there. Then, there’s the possibility of past life, with the ‘canals’ and craters possibly having been hosts to a vast amount of liquid water, when Mars had a thick atmosphere to hold that water, contrasting to todays thin and carbon dioxide rich atmosphere.
Then, there’s the alien tectonics (different to Earth’s more active system) which create ‘marsquakes’, the tallest volcano in the Solar System (Olympus Mons) and one of the largest canyons in the solar system (Valles Marineris) [23].
Valles Marineris Topographic View. Credit: PD-NASA
Game Over
Apart from the obvious challenge with leaving on time (yes, you really do need to hurry up or we’re going to be late!), there’s also the challenge of the “Seven Minutes of Terror”. This devilish sounding event is the time taken to reach the ground of Mars from entry into its atmosphere.
Because of Mars’ distance from Earth, at 204 million km, it takes over 11 minutes (greater than the time for the descent) to transmit a signal across that distance in order to control the descent. Therefore, instead of direct commands, the whole descent is programmed, so if one thing is calculated incorrectly, the whole mission is over [3]. This was seen in the 1998 NASA mission to Mars called “Mars Climate Orbiter”, which failed due to a navigation error from an error translating imperial units to metric [4].
Then, because of the thin Martian atmosphere, there are a whole host of technologies, from sky cranes to parachutes to booster rockets, that are employed to slow the spacecraft down from 19,300kph (for the NASA’s Perseverance mission) to 0kph, in just 7 minutes, in very thin air [3].
This “Seven Minutes of Terror”, along with the ordeal with needing the correct trajectory in order to get into orbit or down to Mars, has cost the lives of a lot of missions in the past: 28 have failed compared to 19 that succeeded, meaning the chances are against them. However, with improved technology and maths skills (yes, I’m talking to you Mars Climate Orbiter!), chances of getting to the ground increase all the time.
Curiosity Rover Sky Crane artist impression. Credit: NASA/JPL-Caltech
UAE’s Hope
The UAE have sent their first mission to Mars (a first for the Arab world too), named “Hope”. It aims to be Mars’ first weather satellite, giving a better picture of its climate dynamics and Mars’ weather patterns and variations, and how it effects the loss of hydrogen and oxygen the Martian atmosphere, still happening to this day, being why Mars has such a thin and perilous atmosphere [5][6].
It didn’t land on Mars, but after a mission that started at Tanegashima Space Port on 20th July 2020 [6], it went into the Martian orbit on 9th February 2021 [7], hitting just the right trajectory to be captured by Mars’ gravity and given a stable orbit around the planet: one that’s intended to last for 1 Martian Year (or to us mere earthlings, 687 Earth days: nearly 2 years [8]) [6].
There are three bits of kit onboard (all modestly beginning with “Emirates”):
Emirates eXploration Imager (EXI): Images the atmosphere in 3 visible and 3 ultra-violet wavelengths to measure dust, water ice and ozone abundance.
Emirates Mars InfraRed Spectrometer (EMIRS): Measures dust, water ice, water vapour and temperature in the atmosphere.
Emirates Mars Ultra-violet Spectrometer (EMUS): Measures hydrogen, oxygen, carbon monoxide, as well as the atmosphere’s seasonality, impacts of the Sun on it, and the winds in the lower atmosphere [9].
All these will work together to get a better picture of the less understood Martian atmosphere.
Martian water ice clouds from Mars Pathfinder. Credit: NASA/JPL
China’s Tianwen-1
This is also China’s first time at the red planet, it’s attempt in November 2011 called “Yinghuo-1” (“firefly”) having fallen back to Earth after having been launched [10], but China’s Mars initiative has had a revamp, now called “Tianwen-1” (“Questions to Heaven”), and was launched on 23rd July 2020 from China [11], arriving into Mars’ orbit on 10th February 2021 [12].
It’s a two part mission, consisting of an orbiter and a rover. The satellite, now in orbit, will observe the characteristics of the Martian upper atmosphere, as well as the surface’s structures and compositions, with some onboard medium-resolution cameras to send back some fantastic pictures from above [13].
The rover, with no name announced as of yet, will attempt the “Seven Minutes of Terror” in May this year, landing in Utopia Planitia (a crater with a possible water deposit the size of Lake Superior in North America) [12], near where Viking 2 landed, but nearer to the Martian equator. It looks rather like NASA’s early Spirit and Opportunity rovers, equipped with cameras for pictures and navigation, and five more instruments for assessing the mineralogy of local rocks (including radars for looking at Mars’ geological layers) and seeking the presence of water-ice [13]. If successful, it will be the first mission to incorporate a satellite, rover and lander all in one hit.
This mission could then be China’s precursor to a sample-return mission, like with their recent sample return mission to the far side of the Moon (Chang’e 4 [14]), meaning the Martian rock can be scrutinised even further [12].
Tianwen-1 Rover artist impression. Credit: CNSA, CC BY-SA 4.0
NASA’s Perseverance Rover
NASA is the only one out of the three to have been here before, with extensive experience of the challenges of arriving and landing on Mars. It is also the most groundbreaking, with a lot of kit to look for a lot of things.
The rover the size of a car with a $2.7bn price tag (£1.93bn) landed on Mars on 18th February 2021 (having set off 30th July 2020) to look for signs of ancient life, and will fill large test tubes full of Martian material and drop them at points on Mars’ surface to then pick up at a later date, and send to Earth to process [16][17].
There are 23 cameras for colour and 3D imagery (shooting high resolution 20-megapixel images) [15] plus a microphone for the full effect [17]; along with a drill to gather core samples for the test tube caches; technology to extract oxygen from Mars’ atmosphere (for testing so we learn more to aid future human missions); and sensors for monitoring the Martian weather and dust, helping to understand the Mars’ daily and seasonal weather variation (to name just a few experiments onboard) [16].
And it’s not just a rover: it’s got a mini-helicopter the size of a chihuahua, called Ingenuity! It’ll fly to places such as cliffs and craters, where the rover isn’t adapted for. With blades spinning at ~2,400 revolutions per minute (8 times faster than Earth helicopters), it has two cameras (black and white, as well as colour) [17] and can fly for up to 90 seconds at distances of 300 metres (aiming for 1+ flights in 30 days), but as the first Martian flight in history, this is still a wonder to behold [18].
The landing site is the Jezero Crater, full of hazards like sand, rocks, and cliffs: a place too dangerous for previous missions to go to, but with modern technologies to plot a trajectory into an area free of these hazards, the rover has a greater chance to land safely on Mars [19]. It’s interesting because it’s a crater that was once a lake (possibly up to 250m in deep) with river deltas (the perfect place to get biomarkers -signs of life), but is also very old [20].
All these missions, as well as other missions on and around Mars already, are all helping us get a better picture of this alien planet, so we can better understand our own planet, as well as other rocky planets; and have the chance to find alien life, so we can see how different Martian life is to Earth’s, to get a better view of how life began, and so how common it is in the Universe.
Perseverance Rover's First Image. Credit: NASA/JPL-Caltech
by George Abraham, ADAS member
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References
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