The Moon and Mars are very different places, but for the last 40 years, the idea of sending humans to Mars has been tied very closely to the idea of a return to the Moon. However, whether this point of view has helped or hindered either a return to the Moon with a human presence or the goal of sending humans to Mars is highly debatable.
In 1989, for example, NASA was challenged to develop a plan to get humans back to the Moon and then on to Mars. Much was made of the idea that the former was necessary because it would ultimately make the means to reach the latter easier and cheaper; however, the blueprint NASA eventually proposed for achieving both a return to the Moon and the onwards exploration of Mars – called the Space Exploration Initiative – required a 30-year time frame to complete and a bill of US $450 billion – or more in comparable terms, than the United States spent on World War 2. Result: any idea of going to the Moon or Mars was quietly pushed aside in favour of just building the International Space Station.
Much of this plan cited the idea that the Moon could be used to form a “cheaper” launch venue for reaching Mars and elsewhere in the solar system, with materials gathered from the surface of the Moon making it “cheaper” to build and test the required hardware needed to reach Mars, whilst the lunar environment could offer the means of testing technologies needed in the attempt to reach Mars such as landing systems, use of local resources. Similar claims were made in the early 2000s with NASA’s Vision for Space Exploration, which similarly ended up pushed to one side on the grounds and time frame.
In actual fact, when things like the amount of energy required to launch humans to the Moon and to launch them to Mars, there is actually very little difference – in fact, when you take into consideration the energy needed to slow a mission into lunar orbit, the energy needed to land it on the Moon, and the energy to re-launch from the Moon to reach Mars, and going to Mars via the Moon actually becomes more expensive in terms of your energy budget – particularly when you consider that regardless of whether they go directly to Mars or via the Moon, all crews will commence their mission directly from Earth. And when you add in all the costs and complexities involved in developing a lunar launch capability – fabrication facilities for vehicle production, development of fuel depots and so on – then the bill for going to Mars via the Moon starts to outstrip the bill for going to Mars directly from Earth.
This point was pretty much demonstrated in the 1990s by aerospace engineers Robert Zubrin and David Baker. Following that US $450 billion bill, they looked at how humans to realistically and cost-effectively be taken to Mars and back safely. Their work resulted in the Mars Direct mission proposal which, in 1996, would have cost around US $10 billion for the first mission and then $1 billion per mission thereafter, with two launches taking place every 2 years.
While there were issues with the Mars Direct proposal (for example: the small number of crew – just 4 people – in the original profile, and a certain cavalier attitude towards cosmic radiation exposure), it offered a “lifeboat” option for getting a crew back to Earth, and it held up to scrutiny as a practical means to reaching Mars within a 10-12 year development cycle. So much so, in fact, that it became the basis for a generation of NASA Mars mission proposals (the Design Reference Missions), and former NASA Administrator Michael Griffin pushed the agency into starting work on the development of the Ares launch vehicles identified as being required for the Mars Direct proposal, under what became known as the Constellation programme (although ultimately, Constellation was cancelled after just one flight of an Ares 1 booster to make way for the Space Launch System).
In terms of technology development, the Moon is also of questionable benefit in terms of missions to Mars. Much has been made of testing landing systems for use on Mars through missions to the Moon, but the fact is, such tests are of limited value: the Moon has little practical atmosphere, ergo, there’s no means to test atmospheric entry systems. A lunar landing also requires an entirely propulsive means of slowing a vehicle and bringing it to a safe landing. However, the tenuous Martian atmosphere allows for aerobraking as both the demands of atmospheric entry and immediately afterwards. It also allows the use of a certain degree of aerodynamic flight capabilities and – potentially and depending on the mass of the landing vehicle – the use of parachute braking systems in addition to propulsive means of slowing and landing.
Similarly, while there is plenty of scope for in-situ resource utilisation on both the Moon and Mars – the production of fuel stocks, air and water, for example – the fact that Mars has an atmosphere that can be used in the production of these elements, whilst on the Moon they must be obtained through processing the regolith, again means the respective technologies needed for doing so on Mars are very different to those needed on the Moon.
So does this mean the idea of using the Moon as a proving ground for going to Mars is a complete misnomer? Not entirely. There are opportunities for testing technologies and procedures that will be required on Mars through a human presence on the Moon – but they do need to be put into perspective. And this is pretty much the findings that have come out of the annual Humans to Mars summit organised by Explore Mars and held virtually at the start of September 2020.
In particular, the summit noted that currently, we only have two data points for human activities in gravity environments: hear on Earth, and the micro gravity environment of Earth orbit. Therefore, even though the Moon’s gravity is half that of Mars, it would still provide a vital data point on things like muscle atrophy and bone calcification, cardiovascular impact, etc., allowing scientists gain greater information on how the human body adapts to a range of gravity environments over extended periods.
Also, things like basic rover systems for use on Mars could be practically tested on the Moon, because when all is said and down, engineers estimate that the requirements for a pressurised rover vehicle intended for use on Mars are around 70-80% the same as those for a pressurised rover intended for use on the Moon. The Moon also offers the potential for testing automated systems that could play a significant role on Mars: such and guidance systems for landings, self-deploying base stations, etc.
Crew activities could also benefit from lunar operations – although here, caution should again be exercised. For example, the summit identified the use of the Lunar Orbital Platform-Gateway (LOP-G) as a means of simulating transit flights to / from Mars to study the physical / psychological / practical challenges of 6-7 month transit times – but frankly, work like this could be carried out just as effectively from Earth orbit. However, options for providing greater protection against cosmic and solar radiation could benefit enormously from lunar-based testing.
Overall, the idea of integrating lunar and Mars mission requirements – where there are natural and genuine cross-overs – could ultimately assist humanity’s move from going back to the Moon to moving onwards to Mars than might be the case in viewing them as separate goals. But in order for this to work, how using the Moon to genuinely assist in undertaking human mission to Mars needs to be clearly understood and stated. The report from the Humans to Mars summit, although it does contain one or two questionable assertions, is nevertheless a positive step towards doing so.
NEOs: One Reason Why Amateur Astronomers are Important
There’s been a lot of late about near-Earth objects (NEOs) – asteroid that can come close to Earth in their orbits and so present a risk of striking Earth at some point. For example, on August 31st, I wrote about this over-excitement around 2018 VP₁ despite the fact it can never present a significant threat (see Space Sunday: Venus’ transformation, SLS and an asteroid).
However, on September 10th, 2020, a much larger asteroid crossed Earth’s orbit, and served as a reminder that there are sizeable bodies out there we have yet to find and which could represent a serious threat – and the importance of amateur astronomers in finding them.
2020 QU6, measuring roughly a kilometre across, passed by Earth at a distance of 40 million kilometres. That’s far enough away for it not to be classified as a near miss, although its orbit is still being assessed to see if it might become a future threat. Certainly, given its size, 2020 QU6 is substantial enough to cause a massive level of devastation were it to make contact. However, what is of key interest here is that, just two weeks prior to its passage past the Earth it was entirely unknown.
Despite its size, 2020 QU6 was not stopped until August 27th, 2020, when amateur astronomer Leonardo Amaral, working at the Campo dos Amarais observatory in Brazil, observed it for the first time. A keen asteroid hunter,Leonard identified the asteroid using equipment he had obtained via a 2019 grant from the Planetary Society that allowed him to significantly upgrade his equipment. In this, he is part of a global network of amateur astronomers the Planetary Society support in the work hunting down asteroids that might pose a threat to Earth.
Thus, his discovery of 2020 QU6 both underlines the importance of amateur astronomers in the finding and tracking of NEOs – particularly given that the major space agencies believe they’ve thus far only identified around 90% of large NEOs that pose a very significant threat to Earth should they collide with us. Leonardo’s work also highlights the importance of amateur astronomers operating in the southern hemisphere, where the larger agencies carrying out similar work don’t have such a pronounced presence as they do in the northern hemisphere., so there is a greater reliance on professional and amateur astronomers. This in a particularly valid point to remember, because knowing there could still be several hundred objects of 1 km or larger routinely crossing the orbit of Earth that we’re completely unaware of is a little unsettling.