NASA has some glossy marketing pages detailing the efforts of the international community in Mars exploration. This is based on their Artemis Moon to Mars program. In there, behind each mission, be it an orbiter, a lander, or a rover, there are critical details about the mission intent. In addition, the pages tell the story; what happened, what did we want to learn on the road to finding relevant and practical landing site for future human mission.
I have collated below the proposed human landing sites for SpaceX and the screened mission locations for NASA. I've also annotated rover locations (current and previous) to show where we have 'visited' so far. Note there is no direct overlap, however all mission sites are proposed within the middle band of Mars where temperatures are highest and solar radiation are its strongest.
Topographical map overlaid with a reddish colour atlas of Mars human mission locations, annotated with SpaceX and NASA candidate sites. Blue rover icons indicate previous and currently live rover missions. Credit: HumanMars, RonnieWrites, NASA/ Wikipedia.
Here we can compare the NASA promoted potential landing sites, against the SpaceX recently screened 7 landing sites. For a more full listing of pros' and cons' for these landing sites - visit HumanMars.net.
First: NASA landing sites
The cut below is a good view of the distribution of NASA-preferred landing sites which were shortlisted for the Perseverance Lander mission. It is a good bet that these sites have significant overlap with future Human lander missions. This is because whatever the humans will need - Water-ice for water/ hydrogen/ oxygen source, or minerals source, is precisely what the rover/ lander missions are looking for.
Even if rover/ lander missions look for evidence of previous life on Mars - this often comes in areas where there is also visible action from water, in mineral rich areas. Eager eyes can see this shows the strength of the assumption underpinning our understanding of how life forms in the Universe:
For life to happen, different material, minerals, organic compounds --> stuff needs to come together closely and interact in presence of an energy source. Having water around doesn't hurt either.
Additionally, these sites all sit within the middle latitudes of Mars. This is because Mars has a tilt, like Earth - and as a result, the areas outside the middle band of Mars get very cold. This also has a detrimental effect on life, inhibiting the ability of microbes to fulfil life functions. At these - 74 degC temperatures (and very often below at the poles), even chemical reactions needed for respiration, cell replication are stopped because the material is frozen solid and cannot move.
This is the same principle behind freezing cell samples and even how home freezer units work - significantly slowing the movement of microbes.
Underpinning NASAs landing site checklist is the following principles (Credit:NASA):
- Can the Mars 2020 rover achieve all of the mission's scientific objectives at this site?
- Does the area show signs in the rock record that it once had the right environmental conditions to support past microbial life?
- Does the area have a variety of rocks and "soils" (regolith), including those from an ancient time when Mars could have supported life?
- Did different geologic and environmental processes, including interactions with water, alter these rocks through time?
- Are the rock types at the site able to preserve physical, chemical, mineral, or molecular signs of past life?
- Is the potential high for scientists to make fundamental discoveries with the samples cached by the rover, if potentially returned to Earth someday?
- Does the landing site have water resources (water ice and/or water-bearing minerals) that the rover could study to understand their potential use by future human explorers?
- Can the rover land and travel from place to place without facing significant hazards posed by the terrain?
The last one is a key one - Can machines travel around without getting stuck in loose martian terrain. This will be a critical one for humans looking for a home from home, to travel around the surface with relative ease, perhaps with a Mars-hardened Cybertruck.
Second: SpaceX Landing sites
SpaceX has taken a very targeted look at landing zones for its proposed future missions. You can see in the mission photo below - the landscape looks vastly different to that above. This is because the capture for SpaceX shows the actual land / water map and elevation difference. The blue areas being low lying frozen oceans and the red areas, high mountains and plateaus.
SpaceX has opted to review 7 landing sites within two specific areas: 6 sites in Southern Arcadia Planitia East of Erebus Montes and one in Phlegra Montes. This is very much more targeted than the NASA mission brief, and what drives it is a distinct and more detailed set of site screening criteria as below:
- close to significant deposits of water/ice, a required resource for in situ propellant production and a consumable to support habitation;
- elevation below -2 km (with respect to the MOLA geoid) that can support the delivery of large payloads, with -3 km preferred;
- latitude must be <40° for solar power and thermal management, and closer to the equator is desirable;
- multiple separate landing locations spaced within a few km of each other, to support the multiple missions needed to grow an outpost;
- slopes should be <5° over a 10 m length scale and the chance of impacting a rock greater than 0.5 m high (1 m diameter) should be <5%;
- landing site must be radar reflective to enable measurement of the distance to the surface, and it must be load bearing to support the spacecraft at touchdown.
Here in the SpaceX brief, we can see specific reference to mission critical parameters which must be met:
- Deposits of water ice - for propellant and human consumables.
- Location must support solar power and thermal management - too cold and dark, will not cut it. The humans need power to survive and then thrive.
- Slopes and impacting rock thresholds - ensure safety in traversal of the human crew as they explore their new home. If the Martians get stuck in a sand drift, it'll be a stressful time to try and escape.
- The site must be load-bearing - with Starship weighing in at 120t dry - unladen and unfuelled, and 1320 tons fuelled. This is a heavy load, a lot of load distributed across a small area - Especially on Starship's landing legs.
Enabling successful landing will be critical, because even successful preparation missions rely on successful safe deployment to conduct their mission. Preparing a suitable landing area for a Starship will be a challenge that robot builders may not be able to achieve themselves, without humans. With the SpaceX Boca Chica facility, we have seen piling operations underlying a reinforced concrete slab to give the right level of mechanical strength for launch and landing operations.
If this cannot be achieved at the landing site on Mars, and the Starship doesn't land well, the Crew could likely stuck there for sometime. This sentiment likely underpins Elon Musk's comments about potential high early fatality rate from our first colonists.
Refining Strategy
In the above, I put forward two organisations approaches to successfully landing a human forward operating base on Mars. NASA and SpaceX have have quite different approaches which are driven by philosophy and scope of their work. To be clear, it is not a competition between the two organisations. Certainly this article does not argue a supremacy of newcomer SpaceX over NASA. Indeed to further this point, SpaceX builds upon some of the innovations, insights and discoveries which NASA had uncovered over the years.
First up, the Space Shuttle proved the concept of reusable space vehicles and this inspired generations of kids and STEM students, myself included. Prior to that, NASA and other space agencies had focused on using single use vehicles only - this concept being difficult enough to achieve (SpaceX took 4 attempts to get a successful launch - launch alone - of their first series Falcon 1 rocket). The most powerful single use multi-stage rocket, still to date, being the Saturn V series of rockets from NASA. Even now the closest mass-capable comparison from a private company is the Falcon Heavy, itself still only a partially reusable launch platform.
SpaceX developed the reusable vehicle concept further with their Falcon 9 rocket with landing capability of their first stage. However, being a private company, with limited funds, SpaceX almost went bust some years back in 2008. Everything was staked on the final roll of the dice with the company needing their Falcon 1 rocket needing to launch successfully. This stands in stark contrast to NASA which had and continues to enjoy the backing of the United States Government. Without this significant budget, the organisation would not have been able to deliver the scope and depth of innovation in space-faring technologies that we have seen. Even this budget is seen to shrink as a proportion of the US government spending over time.
On the subject of reusable vehicles, there are quite some takers for this bet on future lucrative companies will seek to tender for NASA supply contracts to help the organisation deliver its mission. Similarly, other startup aerospace firms such as Rocket Labs and Relativity Space will also need to heed any lessons learned from NASA and SpaceX as they seek to participate in the new Space Race.
Strategy for Mars Mission Locations
It is clear from the lead picture at the top of the post, that NASA has a broader approach to Martian exploration. Their missions have looked wider across the Martian surface, exploring the colder highlands toward the middle and southern hemisphere of the planet. This is evidenced by earlier mission rovers Spirit, Opportunity, Curiosity and now Perseverance rovers. By doing this, NASA aimed to:
Spirit - find evidence of the presence of water on Mars
Opportunity - twin of spirit rover, also tasked with finding water and characterising the climate of Mars
Curiosity - Find building blocks of life, investigate chemical and mineralogical resources on the surface, assess atmospheric evolution and existing atmospheric processes. Characterising the radiation hitting the surface.
Perseverance Rover - Rover is a twin of Curiosity, however slightly upgraded, bearing 2 more cameras and a slightly different load-out of scientific payload, including the ingenuity prototype helicopter - aiming to prove the potential for helicopter flight on another planet.
The questions asked by the deployment of these rovers alone, not to mention a host of other missions delivered successfully by NASA demonstrate that NASA seeks answer to some fundamental questions. Chiefly, is water on Mars and how is it present now. What did the planet have in terms of the building blocks for life. These are big, broad questions and the diverse science payloads on these rovers attest to the many ways scientists and engineers seek to answer them.
Held in contrast, SpaceX's mission to investigate putting humans on Mars and developing a Martian colony starts to look rather narrow. This is reflected in a series of landing sites situated on a frozen ocean in the Northern Lowlands of the planet. Here temperatures are relatively moderate and not too cold, approaching 20 degC in Summer.
Furthermore, the lessons SpaceX can gain from developing artificial habitats and human missions off-world are limited again. In the short term, any insights will likely be centred around how to maintain a safe living arrangement for humans off-world, on another planet. This doesn't really dig into the history of the planet, how life could have evolved previously, before Mars lost its atmosphere. These big questions help us understand ourselves, and just how special Earth is and give us strong reasons to care for it. NASA helps unearth these insights.
You can reach me on Twitter: @Ronnie_Writes
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