Breakfast Bytes Blogs

Last July, in the midst of the global pandemic, three spacecraft were launched to escape our globe. They were bound for Mars.

There is a reason they were all launched around the same time. Mars goes around the Sun roughly half as fast as the Earth does. So regularly it is close to Earth, and regularly it is on the opposite side of the Sun. To launch a craft to Mars, you need to launch it when Mars is close. Actually, like shooting a bird with a shotgun, you need to aim ahead, so you launch to intercept Mars when it is close. Mars goes around the Sun once (a Mars year) roughly half as fast as the Earth. A Mars year is 687 (Earth) days, so not far off two years. As a result, there is a launch window to Mars every 2.2 years. One of them was last summer. It takes about seven months to get there, so those craft launched last summer are arriving this month.

A Mars day, the time it takes Mars to rotate once on its axis, is almost the same as an Earth day, just 40 minutes longer. Actually, that's not quite correct, that is the solar day, the time it takes for the sun to appear in the same place in the sky the following day. On Mars, this is also known as a sol. Because planets are going around the sun as well as rotating about their axis, the solar day requires the planet to rotate just a little further each day to get the sun back in the same place (say overhead). The sidereal day on Mars, rotation measured not by the sun but by the fixed stars, is slightly shorter, just 37 minutes longer than an Earth day. That's an Earth solar day, what we normally just call a day in everyday life. An Earth sidereal day, which takes the yearly orbit of the sun into account, too, is just 23 hours 56 minutes.

Mars is a difficult planet to land on, compared to the moon (no atmosphere to speak of) or Venus (thick atmosphere). Or Earth (I think you know about the atmosphere there). On Mars, there is an atmosphere, but it is thin, so you need to use rockets (like landing on the moon). But it is thick enough that it cannot be completely ignored, and you also need heat shields and parachutes. Compared to landing on the moon, where you need rockets but no heat shields, or on Earth, where you need heat shields and parachutes but no rockets, landing on Mars is the worst of both worlds, requiring everything.

Here's a video that goes into more detail about why landing on Mars is so hard (three minutes):

Another complication: for speed-of-light reasons, it takes about eight minutes for signals from Earth to reach Mars, or rather to reach a spacecraft at Mars. So any landing sequence or entering orbit sequence has to be completely pre-programmed and any decision-making automated.

By the way, half of the fuel required to get to Mars is just to get into Earth orbit. See my post "If You Can Get Your Ship into Orbit, You're Halfway to Anywhere"

UAE Mars Hope

The United Arab Emirates' first mission to Mars is called Mars Hope. As I write this, it is due to arrive on February 9 (next Tuesday) and then enter a low orbit (1000km). It is not designed to land. Instead, it is planned to spend an entire Martian year—687 Earth days, remember—in orbit making scientific measurements of the atmosphere (such as why the Martian atmosphere is bleeding off into space).  It launched on July 19, 2020 from Japan, on a Japanese launch vehicle.

China Tianwen-1

China doesn't seem to have announced precisely when their craft, Tianwen-1, is expected to arrive at Mars, but it should be somewhere in mid-February. This one is designed to go into orbit for a couple of months and then descend to the surface. If the landing is successful, they will be the second country to land a spacecraft on the planet (not counting crash landings). It launched on July 23, 2020. By the way, tian (天) means heaven, and wen (问) means question or questions (there are no plurals in Chinese).

NASA Mars Perseverance

NASA's craft, Mars Perseverence, nicknamed Percy, is also planned to land on the planet, landing in Jezero Crater on February 18. It launched on July 30, 2020. It carries various experiments, a rover (just known as Perseverance) and a helicopter drone called Ingenuity.

As I said above, landing on Mars is difficult. Perseverance has to slow down from 12,100mph at the top of the Martian atmosphere to about 2mph to land. It uses a heatshield, then parachutes, then rockets, and finally lowers the landing vehicle onto the surface with cables. This whole sequence takes just seven minutes, known officially within NASA as "the seven minutes of terror". Then they have to wait another eight minutes to find out if the landing was successful or it crashed.

If the landing is successful, Perseverance will be the second NASA rover on Mars. Curiosity is still there and still functioning. It reached 3,000 sols (Mars solar days) on January 12, just a few weeks ago.

Here is NASA's YouTube channel. You should be able to watch the landing live starting at 11:15am Pacific time on February 18.

Here is a video showing the landing sequence (three minutes):

And a video about the Ingenuity helicopter drone (two minutes):

The Moon

Just a teaser. There are three missions tentatively scheduled to go to the moon this year, two NASA (subcontracted to Intuitive Machines and Astrobotic) and one Indian (Chandrayaan-3). If these happen, and schedule slip is common with this sort of mission, they will be towards the end of the year. Unlike going to Mars, the moon is always close to Earth so there are plenty of launch windows.

Learn More

Here is NASA's Mars Perseverance page.

Here is the UAE Mars Hope page (in Arabic and English)

There doesn't seem to be an official Tianwen-1 page, so here is the Wikipedia page on the mission.

Or just Google the names of the missions. There is a ton of information available and lots of videos.

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