Fall Color

My wife and I just returned from a 3-day trip to visit friends and take in the fall color.  The trip took us north to US Hwy 2 from Duluth, MN to Wakefield, MI and then south to Winchester, WI.  My home town is on that route and I have driven HWY 2 both ways to Minnesota and Michigan hundreds of times.  When you are an old man like me with a personality like mine – that means a lot of associations along the way.

The overriding theme of those associations seemed to be feeling grateful, being lucky and particle spirituality.  I have posted about my blue-collar origins in the past.  Much of that comes down to railroads, mines, relatives I never met, and the thousands of people I have interacted with.  The railroaders include a grandfather and a great-grandfather and three more recent railroad employees my father, brother, and uncle.  My earliest introduction to Hwy 2 was driving with my family to Ironwood, MI 30 miles away to pick up my father. He would drive a freight train down to the Fox River Valley, sleep on a locker room bench overnight, and then return to Ironwood rather than our home town.  I never found out why he was never delivered to his starting point.  I was always focused on the image of that hard wooden bench he was sleeping on - especially as he got older and started to look more fatigued.

Railroad jobs were highly valued.  The pay was good if you could work, but there was a seniority system that seemed to string a lot of people along.  It seemed like a prolonged residency program – all of the work and inconvenience and none of the rewards.  There was plenty of work in the local switch yards that my father could rarely get because of that system.  Instead, he worked 40 hours in 4 days and slept on a bench 2 nights per week.  Six decades later that still raises a lot of questions for me and there is nobody around for the answers. 

Apart from the work-related trips, we would drive over to the Upper Peninsula of Michigan (UP) to buy margarine.  Until 1967, Wisconsin had a law that banned adding yellow food coloring to margarine.  Without it the sticks of margarine were an unaesthetically unappealing white in color.  We drove over to Michigan to get the yellow stuff.  Wisconsin became the last state to repeal that law in 1967.           

Hwy 2 starts as an exit off US35N in Duluth. The freeway drops quickly down a long hill to that exit.  From that hill you can see the Richard I Bong Memorial Bridge.  It is an impressive piece of engineering and it seems to be aging well.  We lived there my first three years out of residency training as part of a National Health Service Scholarship arrangement.  I really liked that city even though the lake kept it cold.  When I lived in Duluth, I was a member of the Duluth Speedskating team.  Before we had ice we would do dry land training out to the middle of the Bong Bridge.  Rhythmic side to side motions from an extreme flexed position at the waist.  It was done at night in darkness, in the gales of November, uphill to the middle of the bridge – the highest point -  and back down again.  There were about a dozen of us following a coach who was my age at the time.  By the end of the month, we were on a 400m oval of ice that we flooded ourselves.  

In the summer, I would cycle to my office across the Bong.  That involved 5 miles on the Skyline Drive in Duluth until I could drop down a steep avenue to the bridge.  There were days when I imagined myself in a movie – cycling over Lake Superior to and from work.  It was that unreal.

There were always plenty of sports related travel both ways on Hwy 2.  Football, baseball, basketball, track, canoeing, and kayaking.  We drove over two rivers that I had canoed and kayaked multiple times, including one where I was almost killed twice in one day.  The Montreal River was not very visible from the road, and I was guessing it was fairly tame this time of the year.  In the spring it moves 1800+ cubic feet per second down a steep gradient though a narrow canyon with steep rock walls.  In some stretches the gradient looks like you are going down a staircase.  If you go down in that water, there is no way out. The day I tried it with the friend I was driving to see and 4 novices in 3 aluminum canoes I was trapped against the bottom by a canoe full of water and then an aluminum canoe wrapped around a boulder holding me down. I was lucky to get loose – twice.  

I think about the games played not so much about the scores or seasons. I was quarter miler in high school and think about a qualifying heat I ran in Ironwood. I was trying to run a sub 50 second quarter mile and failed. I really knew nothing about running or training.  When I finally started learning about the biomechanics of running and realized I could train indefinitely – I beat that time at age 45 on the high school track in my home town. 

I thought about football practice and weight lifting back in those days. How much more or less am I lifting now as an old man? In high school we used homemade weights fashioned out of concrete set in coffee cans at the ends of an iron bar.  I think they were estimated to weigh 60-80 pounds.  Our weight-lifting area was behind the spectator bleachers on the football field.  I still get a mental image of all of my teammates and the expressions on their faces going through practice.  I remember who went on to college and where they ended up.  I remembered who is no longer with us and the last time I talked to them.   I remember how hot it could get and how bad all of the equipment smelled.  At times I think about what I would have changed over 50 years ago on those fields.

And then it is on to other friends.  I drive past a court house and think of my friend who took care of it for decades. He never owned a car and would either walk or cycle to this building to makes sure it was running right – even on the bleakest winter night.  As we were driving up Birch Hill - headed east outside of Odanah I had thoughts about coming down that hill in the opposite direction in a 1963 Plymouth Valiant.  My friend Bob – had his father’s car and decided to see how far it could coast from the top.   It was a standard transmission.  He reasoned it would coast a long way.  It’s the kind of thing that teenage boys did before there was an Internet and Smartphones.  I tell my wife the story about a guy from my hometown who was coming down this hill one night on his new Norton Interceptor when he decided to put the kickstand down and crashed.  But the hill is most famous as a line of demarcation between the mild to moderate snowfalls of Wisconsin and the epic ones of the UP.

All the while music is playing in the background.  Rock music by the decade from a streaming service.  No more cassettes or CDs. Just tell the phone what you want.  We had to carry separate briefcases just for the media. I used to be able to sing along to the falsetto parts but no more.  I can strain to hit "Goin' Up the Country" on a good day but no more Steve Perry or old time Robert Plant. I start talking about vocal ranges of rock singers.  I know Grace Slick is a contralto.  I think Jim Morrison was an alto – but might be wrong.  Lately I have been playing his tracks over and over again. I have seen many videos of his band mates praising his lyrical ability. His song Soul Kitchen started playing spontaneously at home as we were leaving.  The music cuts out several times as we go off the grid reminding me that we are streaming and not listening to downloads.

I think about my relatives along the way – the ones with the greatest impact on my life. My life story is one of many tragedies and I start to think about life being tragic.  I have the recurrent thought – “You did not really plan anything – you were just lucky.”  As usual I can’t disprove it.  At no point in my early life along this highway did I say to myself: “You need a plan to (go to college, get a job, join the Peace Corps, avoid the draft. etc).”  My early life was a series of desperate last-minute decisions.  I had to do something.  In some cases, the decisions were failure based. In some cases, I was just moving along to the next failure.  I think about those failures and what I was like at the time. I think about how everything seemed to fall in place after those desperate decisions.  My life seemed out of control until I was in my thirties. 

And whenever I think about that random walk through life, I always end up thinking about my undergraduate professors.  They were people who believed in me and they were not shy about saying it.   They were people who had clear life plans and philosophies and knew how to live life.  They were people very comfortable about living life outside of a blue-collar world. It is still a mystery to me how I thrived at a small, now defunct college by identifying with those professors and realizing I had a genuine knack for academics.  We did summer projects along Hwy 2.  The focus was water chemistry leading us to remote rivers and creeks – in some cases driving down logging roads.  Sampling water and then running all of the analyses ourselves back in the chem lab. In biology classes we would sample the insects and plankton living in streams and rivers and do all of the taxonomy.  It opened up a whole new level of thinking in the place where I grew up.

At some point in the trip my mind wanders to composite particles and elementary particles.  A few years ago, I discovered that protons and neutrons lasted a trillion trillion years (10⁵⁰ to 10⁵² years).  Almost all of the protons were formed when the universe formed.  The protons in my body are 13.8 billion years old and they have plenty of life left in them.  If I am cremated 96% to 98% of my body is oxidized or vaporized as carbon dioxide, water, and nitrogen gas.  My protons are back out into the universe to live again - for billions of years.  If I am buried it takes slightly longer but the same process prevails in the end. That seems like a spiritual process to me, but I am trying to get opinions from experts.  From my own reading it seems consistent with what Spinoza called a single unified and infinite substance identical with God.  He saw individual humans as temporary perturbations in the infinite substance.  I am part way through 2 books on particle physics and the origins of the atoms in the human body from the cosmos.  During a recent phone call with one of my undergrad classmates, he thought my reading and connections to protons over 50 years after our last chemistry class together was quite humorous. 

As we drive through Ironwood, Hurley, and Bessemer – the last time I was here Hwy 2 was just 2 lanes wide.  Now it is 4 lanes wide with a lot of traffic.  Just to the north is Copper Peak – a ski flying hill.  It has been out of business for 20 years but it is being rebuilt with a large grant.  My wife and I watched a ski flying competition there back in the 1980s.  There were three guys from my hometown standing behind us that day. One of them was the funniest guy I ever knew. He was killed in a car accident a few years later.  One of the other guys was the nicest guy I ever knew.  He died in an industrial accident about 10 years later.  The third guy is still alive. He was responsible for my first dental crown when he elbowed me in the mouth playing basketball and broke tooth number 24 in half.  I get an image of all of us standing there, talking, and joking.

When we get to Wakefield, I think of the first time I was there as a kid to visit my aunt and uncle.  My uncle worked in a copper mine setting explosive charges.  As we drove around Sunday Lake to find their house, I remembered a spillway on the opposite side of the lake but did not look for it this time.  We still had 22 miles to go down S. County Hwy 519.   The fall color along that route was spectacular and I don’t know why.  The weather there is probably subject to what is happening on both Lake Superior and Lake Michigan.  At some point big lakes bring the baseline temperatures down, especially in low lying inland areas.       

When we finally arrive at our destination – we are greeted by a couple I have known since 1970.  We stayed in touch through the lean times, the industrious times of medical careers, and now in retirement.  We caught up on families, common interests, activities, and the medical infirmities of aging or as my friend put it “an organ symphony”.  Among the four of us we have 4 knee replacements, 1 shoulder replacement, 1 hip replacement, 3 ablations for arrhythmias, a pacemaker placement, and various other necessary surgeries.   Nobody is upset about it.  The general attitude is do what is necessary to keep going.  There is some reminiscing but not a lot.  I want them to do as well as they want us to do.  The two days we spend there flies by and we are back on Hwy 2 headed home – hoping to see them a lot sooner next time.  On the road again I think of how important this relationship has been.

In the past few years, I have touched on semantics on this blog and the increasingly well-worn phrase: “The map is not the territory.”  My territory as I have outlined it involves extended connections to people at almost every fork in a 274-mile stretch of road.  There are so many of these connections they can be overwhelming, especially considering the emotional aspects.  With a few exceptions it is impossible to estimate the impact of all of these people on my life.  I am always happy to see them and I miss them when I don’t.  Some people reading this might be surprised.  I am considered to be a loner and asocial on the surface but I don’t think many people really are.  Especially if they have an active memory and can recall the details of what happened to them on Hwy 2 or anywhere else. 

They are just quieter…

 

George Dawson, MD, DFAPA

 

Supplementary 1:

I tried to capture some of my personal experience - the way I think most of the time as I went along this trip.  It has a lot of room for improvement - but at the same time it covers a lot of ground.  I debated constructing a diagram of all the people I would think about along this route and probably will at some point laying it over the route on the map.  I also wanted to provide details of how semantic memory automatically created meaning from these relationships but will defer that to another time. I could not include everything and that may seem paradoxical for a guy with few apparent relationships.  

References:

1:  Wenliang Li ,The proton’s next secret. Science 393,663-664(2026). DOI:10.1126/science.aek0574

2:  Spinoza, Benedictus de. "Ethica, ordine geometrico demonstrata." In Opera Posthuma. [Amsterdam: Jan Rieuwertsz], 1677.  (Grapevine Kindle edition and translation – Benedictus de Spinoza.  Ethics. 2023.

Why A Human Being Will Probably Not Set Foot on Mars – and Related Problems

 

I started reading science fiction about space travel when I was a kid. There was no Internet.  Television was all broadcast, grainy, and reception was shaky.  Radio was mostly focused on music.  It was decades after Orson Welles famous radio broadcast of an alien invasion that some people took as reality.  All I had was a bookmobile with a science fiction section.  I still remember the very first book I read from the bookmobile – When Worlds Collide.  By the sixth grade I was writing 3-page science fiction stories myself - largely based on our class following the early space flights.

Over the decades science fiction about space travel progressed significantly. Even though humans made clear progress – it was nowhere near the fictional travels to deep space, federations of planets, and routine interaction with alien life forms. After a brief concern about an invasion by Martians, the more practical sci-fi has focused on travel to and colonization of Mars.  Just focused on Mars the stories have become more realistic from a booming future colony on Mars to a survival film of a solo astronaut on Mars.

Science fiction and fantasies about space travel have moved squarely outside of science fiction and the cinema these days.  They are influencing how billions of dollars are being spent on Wall Street.  Elon Musk has clearly stated that he intends to send a mission to Mars for the express purpose of colonizing it.  He has given several dates for his first Mars mission that have come and gone.  He has modified his statement several times so that it now includes taking human consciousness extraplanetary.  He also has framed this endeavor as a necessary move to save humanity. This post is all about why that will probably not happen and why all of that rhetoric needs to be rejected outright.

From a science perspective and in a single word it comes down the severe biomedical burden of space travel and the ability of humans to protect themselves against these dangers.  The suggested colonization and possible terraforming of Mars (modifying the atmosphere, temperature, and surface to support human life) also creates a massive resource burden on the Earth and its inhabitants.  This post will examine some of those details and whether or not they have been technically solved. 

At first glance Earth and Mars, Earth is an average of 93 million miles from the Sun and Mars is 142 million miles.  Earth is 7,926 miles in diameter compared with Mars at 4,212 miles.  Gravitation on Mars is 38% of what it Is in Earth (acceleration due to gravity = 3.72 m/s² compared to 9.82 m/s²).  Martian soil is toxic in that it contains perchlorates, silica and various heavy metals.  Martian soil has been studied as both regolith (planetary cover) and dust.  Martian dust has a particle size of 3 microns and is composed of silicon (Si), magnesium (Mg), and iron (Fe).  Based on previous experience with lunar dust it is likely that Martian dust will be a common contaminant.  In addition, the soil contains perchlorate compounds (ClO₄^- )  that can alter thyroid function and cause aplastic anemia.  A variety of illnesses can be produced by this dust including pulmonary, gastrointestinal, endocrine, and neurological diseases (see table1, Reference 1). Perchlorate is also a significant contaminant of water on Mars.  There is no free groundwater but water exists frozen under the surface and has been suggested as a source of water for drinking and terraforming.  Several very limited plant experiments have been done with soil simulating Martian soil.  They are typically limited by species tested and no complete match for soil.  An example is that I have not seen is a paper that tests soil containing perchlorate. Plans to extract water from frozen underground glaciers that also contain perchlorate are also not available.

Apart from the soil and water problem there is an associated engineering problem to provide food both for the flight to Mars and post arrival.  For flights all of most of the food would need to be pre-packaged largely because of the large area needed to grow food to feed people.  This is an interesting engineering problem that NASA has been working on for at least 30 years. In order to grow plants for food on Mars it will take a highly controlled environment (pressure, temperature, atmosphere, radiation protection, lighting and irrigation requirements).  These requirements and the rationale are listed in the table below.   

Requirement	Primary Function / Purpose	Key Operational Challenge / Engineering Need
Atmospheric Pressurization	Keeps water liquid inside plant tissues; enables respiration and photosynthesis.	Must maintain >100-150 mbar of internal pressure against Mars' near-vacuum surface (~6.1 mbar).
Climate & Thermal Control	Protects crops from extreme cold (averaging -60 C); maintains optimal growth temperatures.	Requires heavy thermal insulation, active heating systems, and automated humidity control.
Radiation Shielding	Prevents DNA damage, mutations, and cell degradation from Galactic Cosmic Rays (GCRs) and Solar Particle Events (SPEs).	Enclosure must be buried under several meters of regolith, water layers, or placed inside lava tubes.
Substrate & Water Purification	Removes toxic perchlorates (0.5-1%) and heavy metals; provides a clean growing medium.	Requires chemical leaching/flushing of regolith, or multi-stage filtration and reverse osmosis for harvested subsurface ice.  May require long distance transport of ice
Supplemental Spectrum Lighting	Offsets weak Martian solar irradiance (43% of Earth's) and dust storm dimming; drives photosynthesis.	Requires high-efficiency PAR LED arrays, creating a high, continuous electrical power demand.
Buffer Gas Delivery (N2/Ar)	Dilutes CO2 and O2 to prevent atmospheric toxicity, metabolic collapse, and fire hazards.	Requires cryogenic processing units to extract and concentrate sparse atmospheric nitrogen (~2.6% of Mars' air).
Micro-Ecological Inoculation	Provides essential soil microbiomes (nitrogen-fixing bacteria, mycorrhizal fungi) and ensures crop pollination.	Substrates must be manually seeded with bio-engineered microbe cultures; requires mechanical or automated pollinators.
Closed-Loop Waste Recycling	Recovers nitrogen, phosphorus, and potassium (NPK); recycles non-edible crop biomass and grey/blackwater.	Requires onboard bioreactors, composting, or supercritical water oxidation to maintain nutrient cycles without Earth resupply.
Sensors & Pathogen Control	Prevents catastrophic crop loss from fungal spores, viral blights, or gas imbalances in an isolated ecosystem.	Demands continuous HEPA/UV-C air sterilization and automated real-time multispectral monitoring.

 

As noted, the food growing on Mars will require significant electrical energy requirements to design, construct, and maintain the food growing environment.  Controlled growing experiments by both NASA and Russian programs based on the estimate of 2,500 cal/day for each human suggests that 50-100 m² is the required growing area for a combination of plants that will supply the necessary carbohydrates and proteins.  For a relatively small colony of 1,000 people that would translate to 65-100,000 m². An American football field is 7,140 m2 so at the max this would be about 14 football fields in size.  Some Mars promoters have suggested the size of this colony should be 100,000 people.  That would be 247 acres or 0.39 square miles just for food production.

To reduce the size of this facility it would probably be built vertically in 4-6 layers to reduce the ground level footprint to 16-25,000 m².  That would contain 300-500,000 m³ of pressurized air to maintain climate control, humidity, and gas exchange (20-25 m² of crops under optimal lighting produces enough oxygen for 1 person).  Additional engineering requirements would be 360-720 megawatt hours (MWh) of electric power per day, a continuous circulating loop of 5-10 million liters of pure water, and a one-time structural fill volume of 300-500 metric tons of nitrogen.  This is an unprecedented engineering challenge.  Even if it were clear that water could be purified and extracted from Martian ice and nitrogen could be produced from the thin atmosphere all of the initial equipment would all have to be sent from Earth.  That would take 15-30 heavy lift launches to produce a structure of unknown durability and maintenance needs.  There is no room for error given the flight time from Earth of 180 days for resupply.    

The atmosphere on Mars is a more immediate problem than the soil and all of the construction work would need to occur in that atmosphere. A good comparison is seen in the infographic below from the European Space Agency.  Needless to say – the Martian atmosphere as it stands in not compatible with human life.  Living quarters and suits would need to be as climate and atmosphere controlled as food growing areas.

 

A hidden danger that has flown under the radar for some time is radiation risk. The tables below show the actual measured radiation exposure to Apollo astronauts by physical dosimeters.  The Mars estimates were also physically measured in unmanned spacecraft.     

Apollo Crew Radiation Exposure
Mission	Flight Duration	Lunar Surface Time	Average Radiation Dose
Apollo 11	8 days, 3 hrs	21 hrs, 38 mins	1.8 mSv
Apollo 12	10 days, 4 hrs	31 hrs, 31 mins	5.8 mSv
Apollo 14	9 days, 0 hrs	33 hrs, 31 mins	11.4 mSv
Apollo 15	10 days, 1 hr	66 hrs, 54 mins	3.0 mSv
Apollo 16	11 days, 1 hr	71 hrs, 02 mins	5.1 mSv
Apollo 17	12 days, 13 hrs	74 hrs, 59 mins	5.5 mSv

 

Mars Mission Radiation Exposure
Mission Phase	Estimated Duration	Daily Exposure Rate	Phase Total Dose
Transit to Mars	~180 days	~1.8 mSv/day	~320 mSv
Surface Stay	~500 days	~0.64–0.67 mSv/day	~320 mSv
Return Transit	~180 days	~1.8 mSv/day	~320 mSv
Total Mission	~860 days	—	~1,000 mSv (1.0 Sv)

 A couple of radiation anchor points:  a whole-body CT scan delivers about 10 mSv as x-rays.   The NASA suggested lifetime radiation exposure was recently updated to 600 mSv.  That takes into account cancer, cardiovascular, and brain risk (15).  A Mars mission as outlined above exceeds that risk.  Attempted risk mitigation would include faster transit times and burying living quarters underground/regolith on Mars.  But those variables and what could be achieved are unknown at this time.  If the radiation parameters cannot be improved due to the tradeoffs between the amount of shielding and negligible safety gains - long term colonization by the same people would seem to be an impossibility. 

The type of radiation is also important.  In space, the predominant form is galactic cosmic rays (GCRs) originating in supernovae.  GCRs consist 87% protons, 12% alpha particles, and 1% HZE heavy nuclei (Z in this case refers to the atomic number or number of protons) so it can be read as high atomic number and energy. Comparing GCRs to other common forms of radiation show that it is at the level of 100 MeV to over 1,000,000 MeV (10⁸ to 10¹² eV).  A single GCR proton or heavy ion carries 1,000 to over 10,000,000 times more energy than a typical gamma ray.  The physical properties of the radiation also dictate the shielding requirements. X-rays and gamma rays can use high Z materials like lead (Pb) with a lot of electron density.  GCRs must use low Z materials like water or polyethylene with a lot of hydrogen density to prevent secondary neutrons produced from spallation when HZE nuclei hit large nuclei in shielding. That can lead to a tradeoff of space occupied by the shielding volume and the inevitability that some fraction of high energy particles will go through.

GCR is about 85% of the expected radiation burden followed by transient solar flare radiation (10-15%), and background gamma radiation.  The engineering tradeoffs depend on context (flight versus landed), physical properties of the radiation, extra fuel and thrust necessary for the flight, predictability of radiation bursts, and in some cases power requirements in flight.  Unless there is literature I have not accessed, the estimates of total radiation exposure would seem prohibitive for any long-term settlement of the planet.  It is estimated it would require 1-2 meters of regolith over and inflatable structure to drop the GCR and secondary neutron flux down to acceptable levels on Mars.  Even a deep under regolith settlement still has major logistic problems in getting access to purified water, nitrogen for atmospheric stabilization, HVAC for temp and humidity regulation, and the power to run it all. 

The drain on Earth resources has already begun even before the first manned Mars launch.  SpaceX has as one of its funding sources the Starlink satellite system.  Starlink was designed as low altitude satellite system to provide Internet access in areas with no cable or fiber optic access. The low altitudes are necessary to reduce transmission latency necessary to real time communication. Because of the low altitudes and the curvature of the Earth, thousands of networked satellites are necessary.  An estimated 11,110 functioning satellites are currently in low Earth orbit (LEO).  Six hundred to a thousand of these satellites fall out of orbit each year (1-3 per day) burning up in the atmosphere. 

In 2026 there will be 100-110 Starlink satellites launched to replace the satellites falling out of orbit.  Future projections are for 4 to 5 satellites re-entering every day—or 1,500 to 1,800+ satellites falling out of orbit every year.  SpaceX has 2 rockets to replace these satellites – the Falcon 9 that can carry up to 24 satellites and the Starship that can carry up to 60 satellites.

The environmental burden is significant.  Each Falcon 9 launch injects soot into the upper atmosphere where it remains much longer than on Earth (3-5 years). That soot absorbs solar radiation and has a 500-fold warming impact on the planet compared with ground level soot.  As the satellites reenter and burn up aluminum oxide nanoparticles are generated increasing the risk of ozone depletion and potentially reflect or absorb incoming solar radiation.

All things considered, the information I can find on the planned expedition and colonization of Mars has numerous red flags.  The bottom line is that it is a massive engineering undertaking that presents a significant risk to anyone willing to take a trip to Mars.  I highlighted some of the main risks here but there are many additional details including a paper written about how to treat radiation sickness during the flight. I did not touch on the background effects of weightlessness and the associated syndromes.  They are significant and require physical training effort to minimize. Any routine illness in space will not be the same routine illness that would have happened on Earth.

And the question is – to what end?  Are we really expanding human consciousness into the cosmos – or sending it to a miserable demise? Is staying on Earth putting all of our survival eggs in one basket or is it the best rational decision to keep us alive?  And what about the conflict-of-interest issues. The space business is no longer a government enterprise carrying forth the aspirations of mankind.  It is a multibillion-dollar, for-profit, publicly held enterprise.  The colonization of Mars is estimated to cost over a trillion dollars.   That is heavy financial incentive for hyping space travel and ignoring the current significant environmental costs that are now funding it. 

I have done a significant amount of research on the extraterrestrial issue and debated another long post on that topic but I will cut to the chase here instead.  There is no evidence that Earth has ever been visited by extraterrestrial beings.  The distances are too great, and the recorded aerial phenomena too weak to consider as evidence. That does not mean there are not other intelligent life forms out there – only that if there are - they have not visited Earth.

Planet	Mean Surface / Effective Temp (°C)	Mean Surface / Effective Temp (°F)	"Surface" Definition
Mercury	167 °C	333 °F	Surface varies wildly: -180 °C (-290 °F) at night to 430 °C (800 °F) by day.
Venus	464 °C	867 °F	Solid surface; runaway greenhouse effect creates a uniform, scorched temperature.
Earth	15 °C	59 °F	Solid surface.
Mars	-65 °C	-85 °F	Solid surface; thin atmosphere causes large swings (-125 °C to 20 °C).
Jupiter	-110 °C	-166 °F	Measured at 1 bar pressure level (no solid surface).
Saturn	-140 °C	-220 °F	Measured at 1 bar pressure level (no solid surface).
Uranus	-195 °C	-320 °F	Gas of atmosphere transitions into a thick, fluid interior without a clear boundary or solid ground.  Measured at 1 bar pressure level; drops as low as -224 °C (-371 °F) in the upper atmosphere.
Neptune	-200 °C	-330 °F	Measured at 1 bar pressure level (no solid surface).

 

Just looking at planet surface temperature and their increasing distance from the sun it seems obvious why Earth is the only non-hostile environment for humans.  All of the hype about “expanding human consciousness to the universe” or “a humanitarian argument for making life multi-planetary”, or that it is “too risky to put all of our eggs in one basket” – is just that.  As far as preserving Earth goes – I can’t say it any better than Carl Sagan:

“It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.”

— Carl Sagan, Pale Blue Dot, 1994

Be more like Carl Sagan and less like the legion of politicians and entrepreneurs destroying the only home we will ever know.         

  

George Dawson, MD, DFAPA 

Supplementary 1.  Radiation Risk from Standard X-rays: I thought I would add an explanatory paragraph on radiation exposure in space and dosing compared to standard x-rays.  Recall that x-rays are photons and galactic cosmic ray (GCRs) are particles.  It is calculated from the absorbed dose in Gy (where 1 Gy = 1 J/kg).  That absorbed dose is multiplied by organ and tissue weighting factors to reflect the potential for injury.  For radiation in space Linear Energy Transfer (LET) of high energy particles is used for the exposure calculation (1).  That equation is:

H = D × Q ,

where D = (physical energy deposition) absorbed dose in energy per unit mass.

Q = quality factor - continuous function of the particle's linear energy transfer (LET), ranging from 1 for low-LET radiation (photons, fast protons) up to ~30 for densely ionizing heavy ions. There are 2 competing models for Q.

H = (risk relevant biological dose) dose equivalent of biologically equivalent dose (mSv).

 

The important concept in looking at equivalent radiation doses between photons (x-rays, gamma rays) and particles (GCRs) is that GCRs are not directly measured and are estimates based on both the 2 models of the Q factor and the particle composition of the radiation. The HZE particles that drive the radiation dose in space for astronauts are elements 2 (Helium or He) to 26 (Iron or Fe).

In the simpler case on Earth, medical x-rays have been studied.  Several of those studies show a higher risk of malignancy with more x-ray exposure. The table below gives the effective dose and dose relative to background radiation (on Earth) for a number of procedures.  Longer procedures like CT scans and fluoroscopy have higher radiation exposure.  Compare to Mars Mission Radiation Exposure (3rd table above).

 

Modality / study	Typical effective dose (mSv)	Multiple of a chest X-ray / background	Cancer-risk context	References
Chest radiograph (PA)	0.02	1× (baseline)	Negligible; pediatric attributable risk <1%	[2, 3]
Panoramic/intraoral dental	0.01	~0.5×	Negligible	[2, 4]
Mammography	0.4	~20×	Very low	[2, 4]
Lumbar spine (3 views)	1.5	~75×	Low	[2]
CT head	~2	~100×; ~2/3 of annual background	Bone-marrow dose ~13.7 mGy; pediatric RR ~1.35 for hematologic cancer	[1-3]
CT chest	7 (range 5–13)	~350×; ~2 yr background	Small individual stochastic risk	[1-2, 5]
CT abdomen/pelvis	14 (range 10–17)	~700×	One of the higher routine CT doses	[2, 5]
CT pulmonary embolism protocol	15	~750×	Higher because multiphase	[2]
Multiphase / combined CAP CT	~30–40 (cumulative)	approaching detectable-risk threshold with repetition	~1 in 100 lifetime cancer per 100 mSv (BEIR VII)	[2, 5]
Nuclear stress test (sestamibi 1-day)	9.4	~470×	Moderate	[2]
Nuclear stress test (thallium)	40.7	~2,000×	Among the highest routine studies	[2]
Diagnostic cardiac catheterization	7	~350×	Operator- and case-dependent	[2]
Coronary stent / PCI	15	~750×	Higher with complexity	[2]
Interventional/fluoroscopic procedures (range)	5–70 (up to >250 for portography)	highly variable	Skin injury threshold at ~5 Gy air kerma triggers follow-up	[1, 6]
1.  Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008 Jul;248(1):254-63. doi: 10.1148/radiol.2481071451. PMID: 18566177. 2.  Ford B, Dore M, Moullet P. Diagnostic Imaging: Appropriate and Safe Use. Am Fam Physician. 2021 Jan 1;103(1):42-50. PMID: 33382559. 3.  Smith-Bindman R, Alber SA, Kwan ML, et al. Medical Imaging and Pediatric and Adolescent Hematologic Cancer Risk. N Engl J Med. 2025 Oct 2;393(13):1269-1278. doi: 10.1056/NEJMoa2502098. Epub 2025 Sep 17. PMID: 40961449; PMCID: PMC12445590. 4.  Ahmed NA. Typical effective dose values from diagnostic and interventional radiology. Appl Radiat Isot. 2023 Feb;192:110611. doi: 10.1016/j.apradiso.2022.110611. Epub 2022 Dec 7. Erratum in: Appl Radiat Isot. 2026 Jun;232:112543. doi: 10.1016/j.apradiso.2026.112543. PMID: 36516635. 5.  Smith-Bindman R, Moghadassi M, Wilson N, Nelson et al. Radiation Doses in Consecutive CT Examinations from Five University of California Medical Centers. Radiology. 2015 Oct;277(1):134-41. doi: 10.1148/radiol.2015142728. Epub 2015 May 19. PMID: 25988262; PMCID: PMC4613871. 6.  Li X, Hirsch JA, Rehani MM, Yang K, Liu B. Effective Dose Assessment for Patients Undergoing Contemporary Fluoroscopically Guided Interventional Procedures. AJR Am J Roentgenol. 2020 Jan;214(1):158-170. doi: 10.2214/AJR.19.21804. Epub 2019 Oct 31. PMID: 31670595.

 

The strongest recent human evidence comes from the 2025 NEJM cohort of 3.7 million children (3), which found a linear dose-response for hematologic cancer detectable below 50 mGy — a relative risk of ~1.8 at 15–20 mGy (roughly one to two head CTs) and ~3.6 at 50–100 mGy — estimating that 10.1% of hematologic cancers in the cohort were attributable to imaging radiation.

It is important to keep in mind that all medical risks are probabilistic and there are additional demographic factors like age, sex, and cumulative exposure and that risk always needs to be balanced against the potential benefit. As an example worldwide a million people each year undergo cardiac ablations for arrhythmias despite the x-ray exposure and a significant number of those people need a repeated procedure.

1:  Naito, M., Kodaira, S. Considerations for practical dose equivalent assessment of space radiation and exposure risk reduction in deep space. Sci Rep 12, 13617 (2022). https://doi.org/10.1038/s41598-022-17079-1  

2:  Smith-Bindman R, Chu PW, Azman Firdaus H, et al. Projected Lifetime Cancer Risks From Current Computed Tomography Imaging. JAMA Intern Med. 2025;185(6):710–719. doi:10.1001/jamainternmed.2025.0505

3:  Smith-Bindman R, Alber SA, Kwan ML, et al. Medical Imaging and Pediatric and Adolescent Hematologic Cancer Risk. N Engl J Med. 2025 Oct 2;393(13):1269-1278. doi: 10.1056/NEJMoa2502098. Epub 2025 Sep 17. PMID: 40961449; PMCID: PMC12445590.

4:  Baerlocher MO, Detsky AS. Discussing Radiation Risks Associated With CT Scans With Patients. JAMA. 2010;304(19):2170–2171. doi:10.1001/jama.2010.1591

Supplementary 2:  How DOGE reshaped NASA and made SpaceX the de facto space agency:

I put this infographic together based on several sources.  After NASA was downsized and several programs shut down - SpaceX became the only means of continuing key operations including manned space flights.  That also resulted in a significant cash infusion into SpaceX.  I have not seen any analysis of the overall cost of privatizing space travel beyond my infographic but this obviously has impacts on the institutional knowledge of NASA and its culture and traditions as well as the entire culture of the US.  NASA is no longer the agency you cheered on as a kid or an adult. A significant part of what it now does is farmed out to a for profit company that in many ways was responsible for weakening it.  (click to enlarge).

 

Graphics Credit:  

1:  Planet Mars.  By Sevinchalisherovna, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0 Unaltered.

2:  Comparison of the Mars and Earth atmospheres is from the European Space Agency ©ESA and it is used here per Common Cause license (see link for details) CC BY-SA 3.0 IGO  It is unaltered and this is a non-commercial and not-for-profit site.

 

References:

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2:  Caston, R., Luc, K., Hendrix, D., Hurowitz, J. A., & Demple, B. (2018). Assessing toxicity and nuclear and mitochondrial DNA damage caused by exposure of mammalian cells to lunar regolith simulants. GeoHealth, 2, 139–148. https://doi.org/10.1002/2017GH000125

3:  Kasiviswanathan P, Swanner ED, Halverson LJ, Vijayapalani P. Farming on Mars: Treatment of basaltic regolith soil and briny water simulants sustains plant growth. PLoS One. 2022 Aug 17;17(8):e0272209. doi: 10.1371/journal.pone.0272209. PMID: 35976812; PMCID: PMC9385024.

4:  Cucinotta FA, Kim MH, Chappell LJ, Huff JL. How safe is safe enough? Radiation risk for a human mission to Mars. PLoS One. 2013 Oct 16;8(10):e74988. doi: 10.1371/journal.pone.0074988. PMID: 24146746; PMCID: PMC3797711.

5:  Brojakowska A, Bisserier M, Eskandari A, Jagana V, Khlgatian MK, Arakelyan A, Fogarty J, Kovacic JC, Goukassian DA. Cardiovascular risks and hazards associated with deep space exploration. Commun Med (Lond). 2026 Jun 23;6(1):354. doi: 10.1038/s43856-026-01728-x. PMID: 42337079; PMCID: PMC13291221.

6:  Narici, L., Baiocco, G., Cenci, G. et al. Radiation risk mitigation in human space exploration: a primer, a vision, and the state of the art. Eur. Phys. J. Plus 141, 100 (2026). https://doi.org/10.1140/epjp/s13360-025-07199-8

7:  Patel, Z.S., Brunstetter, T.J., Tarver, W.J. et al. Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars. npj Microgravity 6, 33 (2020). https://doi.org/10.1038/s41526-020-00124-6

8:  Fogtman A, Baatout S, Baselet B, Berger T, Hellweg CE, Jiggens P, La Tessa C, Narici L, Nieminen P, Sabatier L, Santin G, Schneider U, Straube U, Tabury K, Tinganelli W, Walsh L, Durante M. Towards sustainable human space exploration-priorities for radiation research to quantify and mitigate radiation risks. NPJ Microgravity. 2023 Jan 27;9(1):8. doi: 10.1038/s41526-023-00262-7. PMID: 36707520; PMCID: PMC9883222.

9:  Kernagis DN, Balcer-Kubiczek E, Bazyar S, Orschell CM, Jackson IL. Medical countermeasures for the hematopoietic-subsyndrome of acute radiation syndrome in space. Life Sci Space Res (Amst). 2022 Nov;35:36-43. doi: 10.1016/j.lssr.2022.06.002. Epub 2022 Jun 9. PMID: 36336367.

10:  Ewert, M. K., Chen, T. T., & Powell, C. D. (2022). Life support baseline values and assumptions document (Report No. NASA/TP-2015-218570/REV2). NASA Johnson Space Center.  https://ntrs.nasa.gov/api/citations/20210024855/downloads/BVAD_2.15.22-final.pdf

11:  Monje, O., Stutte, G. W., Goins, G. D., Porterfield, D. M., & Bingham, G. E. (2003). Farming in space: Environmental and biophysical concerns. Advances in Space Research, 31(1), 151–167. https://doi.org/10.1016/s0273-1177(02)00751-2   Abstract at:  https://pubmed.ncbi.nlm.nih.gov/12577999/

12:  Wheeler, R. M. (2020). NASA’s contributions to vertical farming (Report No. NASA TM-2020-5008832). NASA Kennedy Space Center.  https://ntrs.nasa.gov/api/citations/20205008832/downloads/NASA%20TM-2020-5008832%20NASA's%20Contributions%20to%20Vertical%20Farming.pdf

13:  Wheeler, R. M., Mackowiak, C. L., Stutte, G. W., Sager, J. C., Yorio, N. C., Ruffe, L. M., Fortson, R. E., Dreschel, T. W., Knott, W. M., & Corey, K. A. (1996). NASA's Biomass Production Chamber: A testbed for bioregenerative life support studies. Advances in Space Research, 18(4–5), 215–224. https://www.sciencedirect.com/science/article/abs/pii/027311779500880N?via%3Dihub

 14:  Monje, O., Stutte, G. W., Goins, G. D., Porterfield, D. M., & Bingham, G. E. (2003). Farming in space: Environmental and biophysical concerns. Advances in Space Research, 31(1), 151–167. https://doi.org/10.1016/s0273-1177(02)00751-2

15:  Ramos RL, Carante MP, Ferrari A, Sala P, Vercesi V, Ballarini F. A Mission to Mars: Prediction of GCR Doses and Comparison with Astronaut Dose Limits. Int J Mol Sci. 2023 Jan 24;24(3):2328. doi: 10.3390/ijms24032328. PMID: 36768652; PMCID: PMC9916691.