The Changing Face of Mars
Canals and intelligent Martians have given way to a dry, airless and seemingly lifeless Mars.
An awful lot has been written about Mars in both fiction and non-fiction and it would be impossible to summarise it all. Before space probes visited Mars in the 1960s it was often imagined that the dark areas seen through telescopes were vegetation instead of the rocks and lava fields that have now been revealed. The fiction of Edgar Rice Burroughs portrayed the planet with an atmosphere that could support human life which we now know is far from the case but ambitious plans for how large populations could live on Mars are still with us.
Perhaps a good place to start is with Percival Lowell (1855-1916) who was convinced that Mars was criss-crossed by artificial canals that brought water from the Martian polar ice caps to other parts of the planet. To study Mars, Lowell founded an observatory in Flagstaff Arizona where he installed a 24” (51 cm) high quality telescope in an area where the observing conditions are very good. When other astronomers said that they could not see the canals that Lowell reported observing, he said that they did not have the advantage of his sharp eyesight, excellent equipment and good seeing conditions.
Early in his career the astronomer E M Antoniadi (1870 – 1944) drew maps of Mars showing a network of fine lines, but in 1909 when he had the opportunity to use the 33” (83 cm) telescope at Meudon near Paris, he changed his opinion and stated that the canals were an illusion brought about chance alignments of small markings. Others have also seen the alleged canals. A contributor to stargazerslounge.com using only a 5” (13 cm) telescope reported that during the 2003 opposition of Mars, when the planet was closer to the Earth than at any time for nearly 60,000 years, he saw that ‘the planet presented a fractured eggshell appearance.’ He wondered if the illusion was caused by the boundaries between light and dark areas.
I’ve often read about Lowell but I’ve never tried to read anything by Lowell himself until now. It only took a brief dip into Lowell’s 1905 book ‘Mars and its Canals,’ available from gutenberg.org, to discover a surprising error. In chapter 15 he describes how he made a test where he used his telescope to observe a wire stretched across the sky to determine how big a canal he could see on Mars.
He reckoned he could just make out a wire 0.0726” (1.84 mm) in diameter 1800 feet (0.55 km) away. From this he calculated the resolution of his telescope as 0.69 arcseconds. According to asterism.org the theoretical resolution of a 24” telescope is 0.23 arcseconds. The practical resolution will always be greater than the theory so Lowell’s figure of 0.69” seems reasonable. However, he then goes on to calculate, by a process he doesn’t reveal, that: ‘Theoretically, then, a line three quarters of a mile wide [on Mars] should be visible to us.’ He then says that because of practical limitations a canal of a width of two miles (3 km) should be visible at the distance Mars was at that time and about one mile (1.6 km) when Mars is at its closest to Earth.
When I calculate this out taking the closest approach of Mars in 1905 as 80.3 million km (stjerneskinn.com) I get 1.84 mm x 80,300,000/0.55/1,000,000 = 267 km.
Taking another approach; the maximum apparent diameter of Mars in 1905 would have been 17.3”. Which divided by 0.69” = 25.1. The actual diameter of Mars is 6779 km so that in digital imaging terms each ‘pixel’ visible through the telescope would have been 6779/25.1 = 270 km in the middle of the disc. So, subject to some rounding errors, I have the same answer by two different routes.
When you look at Lowell’s drawings of Mars compared with pictures from the Hubble Space Telescope which according to NASA can produce images with a resolution of 0.05,” it’s impressive that, apart from the canals, Lowell was actually pretty accurate. His telescope, which is still in use today, is by all accounts an excellent instrument, but there is a limit to what even it can do.
Here is Lowell’s 1905 map of Mars compared with approximately the same view taken by the space telescope on 20th March 1997 when Mars was 98.6 million km away and the disc was 14.2” across. In Lowell’s drawing South is at the bottom because many astronomical telescopes invert the image and I have turned the Hubble image upside down to match it, so that the North polar cap is at the bottom. I’ve tried to simulate what Lowell would have seen by reducing the definition of the Hubble view so that the disc of Mars is only 25 pixels across
Doubling the definition to 50 pixels gives us:
And with Mars at 75 pixels across we have the approximately theoretical resolution of Lowell’s telescope
Even allowing for the haze in Mars’ atmosphere, it’s hard to imagine why Lowell thought he could see the canals which he spent so much of his life investigating.
https://nssdc.gsfc.nasa.gov/imgcat/hires/m04_11e.gif
It wasn’t until Mariner 4 passed by Mars in 1965, sending back 22 pictures at a rate of a mere 8 bits per second, that we started to realise that Mars is a barren, cratered desert, in some ways, closer to the Moon than the Earth. The area of this 200 x 200 pixels image is 250 km by 254 km making each pixel 1.25 km across which is almost exactly the 0.75 miles resolution that Lowell claimed he ought to be able to see from Earth when in fact he would have only have been able to see the whole area of this picture as a single speck.
Mariner 4 also gave the first accurate indication of the air pressure on Mars of 4.1 to 7 mbar by measuring the effect of the atmosphere on Mariner’s radio signal as the probe passed behind the planet (NASA). The pressure on Earth is around 1000 mbar.
The low pressure on Mars had long been suspected. In 1784 William Hershel noticed that two stars passed very close to Mars with no effect on their brightness due to the atmosphere, leading him to conclude that it was very thin.
In 1925 W.W. Coblentz working at the Lowell Observatory published measurements of the temperature of Mars by detecting infra-red radiation coming from different parts of the surface. The Scientific Monthly, Vol. 21, No. 4 (Oct., 1925), pp. 400-404 (5 pages) https://www.jstor.org/stable/7402
The large difference between daytime temperature and the area emerging from night led Coblentz to correctly conclude that Mars’ atmosphere is ‘rare.’ Coblentz realised that conditions on Mars are much tougher than on Earth but writes ‘…from the way animals and plants adapt themselves to conditions on our deserts it seems possible for life to adapt itself to conditions on Mars.’ He probably didn’t think that the air pressure is less than 1% of that on Earth and is nearly all carbon dioxide.’
The theme of a dry, extreme environment on Mars not dissimilar to the top of a very high mountain on Earth but with plant and animal life is picked up by Arthur C Clarke in ‘The Sands of Mars’ (1951) and Robert Heinlein’s ‘Stranger in a Strange Land’ (1961). The ever practical Clarke recognises that a colony on Mars would have to be self-sufficient. Heinlein’s novel is about a man born on Mars who has been brought up by intelligent Martians. He has a unique view of the world and has apparently magical skills taught to him by his adoptive parents. Heinlein’s ‘Double Star’ (1956) also features intelligent Martians. An out of work actor is hired to impersonate a politician who is unable to attend an important meeting on Mars. It’s an unlikely scenario but Heinlein develops it into an entertaining and thought provoking story.
Curiosity Rover, Gale Crater, 2015 (NASA/JPL-CalTech/MSSS)
Since Mariner 4, a slightly less bleak picture of Mars has emerged. Here we see sedimentary rock indicating that Gale crater was once filled by a lake at a time when the atmospheric pressure was much higher. The scene looks quite pleasant but make no mistake this is a brutal environment with extreme temperatures, virtually no oxygen and high levels of radiation that on Earth are largely deflected by our magnetic field, which Mars lacks. To walk here you would need to wear a space suit similar to that worn by astronauts on the Moon.
When Armstrong and Aldrin walked on the Moon in 1969 it seemed a given that it wouldn’t be long before someone would be doing the same on Mars but it’s not that easy. Unmanned probes going to Mars using a low energy trajectory typically take 6 to 8 months to get there and we could use a similar approach to send people. The only trouble is that you would then have to wait around 18 months before Mars and the Earth would be in the right positions to launch the homeward flight of another 6 to 8 months. An alternative, first proposed in the 1960s, would be to make a flyby of Venus either on the way to Mars or on the return journey. It sounds counter-inuitive but the extra push given by the gravity of Venus would make the overall trip take less than two years. You would only get a month on the surface and in such a short time it would be hard to add much to what decades of robotic exploration has managed to discover. A study by Aerospace Research Central proposed launching a manned mission to Mars in 2033, spending a month on the planet and returning with a flyby of Venus for a total mission time of 1.6 years https://arc.aiaa.org/doi/10.2514/1.A35437 . I’m sure it would be very exciting to visit Mars like this and also have a close-up view of Venus but a trip of this length would surely test the patience of the crew.
The next step is to say, well never mind about just visiting Mars, why not stay there? This was the idea behind Mars One a small organisation in the Netherlands who in 2012 proposed sending 4 people to Mars never to return. When I read their website, I found it very beguiling and then thought, ‘Hang on a minute this is ridiculous.’ They were proposing to set up a manned outpost on Mars for only $6 billion which they didn’t even have. Building the International Space Station cost over $100 billion which is only in low Earth orbit and costs a few billion a year to maintain. It can only sleep six people at a time and has to import all its food and air. Unsurprising Mars One collapsed in 2019 but before that, candidates signed up with them for the opportunity to be launched into the sky for an uncertain future and some serious newspapers and broadcasters reported the proposals without casting any doubt on the project. I’m still not sure whether Mars One was a hoax or if they were misguided enough to think that they could really do it.
Another unlikely plan that featured in the BBC Science Focus magazine and many other outlets, is the proposal to build Nüwa, a city on Mars capable of housing 250,000 people in tunnels with a total volume of 188 million m3. The architect Alfredo Muños, who was a leading member of the design team, said in an interview https://www.dezeen.com/2021/04/07/nuwa-mars-city-cliffside-abiboo/ that building could start as soon as 2054 and with the ‘right resources’ it could be finished by 2100.
Roger Maddrell Chief Engineer (Marine) of Eurotunnel, wrote in IASBE Reports 1991, that the Channel Tunnel between Britain and France created over 7 million m3 of spoil. The building of Nüwa would require excavating around 25 times as much as this. According the Eurostar website it took 13000 workers, not to mention huge tunnelling machines, nearly six years to build the tunnel at a cost of £4.65 billion or about £12 billion in todays money ($15 billion).
Eurotunnel Folkestone terminal John Fielding on Flickr
On this basis we could say that even building Nüwa on Earth could cost in the region of $375 billion ($15 billion x 25) and would take 13000 workers, 150 years to complete. It might be possible, in the long term, to do this on Mars but a target date of 2100 is hopelessly ambitious.
When I look at the billionaire businessmen, Bezos, Branson and Musk who are all building spacecraft I am reminded of the film ‘The Man Who Fell to Earth’ (1976) where David Bowie plays an alien of human appearance who starts a business empire to fund a space program with the intent of returning to his home planet. Elon Musk does come across as a little other worldly at times, but how ever strange we may think Elon is, unlike Mars One, he really does have chance of being able to put people on Mars using his Space X company. He’ll have to manage it better than twitter/X which in January 2024 was widely reported to have lost 71% of its value since he purchased the company in October 2022.
Elon Musk sees Mars as a second home for humanity which could survive if the Earth was, for example, hit by a large asteroid similar to the one that wiped out the dinosaurs 66 million years ago. It would be one thing to visit Mars and maybe even set up a permanent research station like we have Antarctica but a fully functioning, self-sustaining Martian economy which could continue with zero input from Earth would be another story altogether and I will say more about that in my next post.
I'm guessing that in a future post you're going to look at Robert Zubrin's ideas for Martian settlement? He seems to be the person who has given it the most rigorous thought, though whether he makes sense I can't say. Anyway, thanks for this interesting post!
I've never even heard of the Martian Canals before but it is so interesting to look back and see the sort of ideas people had before tech took us so far. It's especially interesting that even if there were never any canals that the idea was enough to drive a man to leave behind a legacy that still mattered in learning more about Mars as a whole.