Many sci-fi writers talk about people traveling to Mars in spaceships. People in NASA claim the same thing, and NASA and the government talk about spending many billions of dollars to soon send manned rockets to Mars.
But that is foolish and probably impossible! The human body seems unlikely to be able to survive the trip to Mars, and probably could not survive living there. Everyone is overlooking some important after-effects of the people who have spent extended time in the Mir and ISS (International Space Station). Everyone who has spent six months in space has discovered that the Microgravity has caused their bones to lose from 16% to 30% of their strength and other physiology such as cardio-vascular to become degraded. Even their eyes and vision are badly affected. A follow-up period of one and a half years of Recovery on Earth is then required. A year on the ISS seems to require three years of Medical recovery on Earth. We should know more about this as Doctors watch how Scott Kelly recovers from his 11 months on the ISS (landing in March 2016).
Here are two NASA medical articles about those Astronauts.
Published - August 19, 2004 - Mostly about Mir Cosmosauts
Life in the microgravity environment of space brings many changes to the human body. The loss of bone and muscle mass, change in cardiac performance, variation in behavior, and body-wide alterations initiated by a changing nervous system are some of the most apparent and potentially detrimental effects of microgravity. Changes to bone are particularly noticeable because they affect an astronaut's ability to move and walk upon return to Earth's gravity.
Structure and Function of Bone
Bone is a living tissue. It is dynamic, responsive to disease and injury, and self-repairing. Bone has both an organic component and an inorganic component. The organic component is composed mainly of collagen, long chains of protein that intertwine in flexible, elastic fibers. Hydroxyapatite, the inorganic component, is a calcium-rich mineral that stiffens and strengthens the collagen. Together, the interwoven organic and inorganic components of bone create a sturdy yet flexible skeletal structure.
The body is constantly breaking down old bone, and replacing it with new bone. Bone is formed by cells called osteoblasts. These cells lay down new mineral along the surface of bone. Osteoclasts, large multinucleate cells, breaks down old bone, and are in part responsible for releasing calcium into the bloodstream. In a healthy individual on Earth, bone is formed at the same rate at which it is broken down, so there is never an overall loss of bone mass. This process changes as a person grows older, or enters microgravity for an extended period of time.
On Earth, bones perform four basic functions:
Mechanical support: The skeleton supports soft tissue and the body's weight. Many bones also act as levers for muscles, enabling movement.
Storage of essential nutrients: Bone stores much of the calcium received from the diet. The calcium is stored inhydroxapatite (the principal bone salt which provides thecompressional strength of vertebrate bone). Between meals, the body maintains a constant concentration of calcium by absorbing it from bone and releasing it into the bloodstream. This constant calcium level in the bloodstream allows proper neural, muscular, and endocrine (hormone) functioning, as well as other cellular activities (e.g., blood clotting). From the bloodstream, the calcium is taken up by different organs and systems of the body. When the body absorbs too much calcium from bones the skeleton can become thin and weak. Bone is also a good source of phosphate, hydrogen, potassium, and magnesium. Like calcium, these minerals are used by many systems of the body for a wide range of purposes.
Production of blood: In addition to essential minerals, bone is also the storage site of marrow. Marrow is important for the formation and development of red and white blood cells and platelets.
Protection: The skeleton houses and protects the
brain, spinal column, and nerves. Many
bones, especially the ribs, also protect the internal organs.
Bone and Microgravity
Some of the processes and functions of bones change after the astronaut has lived in microgravity for several days. In space, the amount of weight that bones must support is reduced to almost zero. At the same time, many bones that aid in movement are no longer subjected to the same stresses that they are subjected to on Earth. Over time, calcium normally stored in the bones is broken down and released into the bloodstream. The high amount of calcium found in astronaut's blood during spaceflight (much higher than on Earth) reflects the decrease in bone density, or bone mass. This drop in density, known as disuse osteoporosis, leaves bone weak and less able to support the body's weight and movement upon return to Earth, putting the astronaut at a higher risk of fracture.
This bone loss begins within the first few days in space. The most severe loss occurs between the second and fifth months in space, although the process continues throughout the entire time spent in microgravity. Extended stays on Mir have resulted in losses of bone mass of as much as 20%. Astronauts regain most of their bone mass in the months following their return from space, but not all of it.
The exact mechanism that causes the loss of calcium in microgravity is unknown. Many scientists believe that microgravity somehow causes bone to break down at a much faster rate than it is built up. However, the exact trigger for this rate change has not been found. Researchers are currently pursuing multiple lines of research, including hormone level, diet, and exercise, in order to determine exactly what causes -- and may control or prevent -- osteoporosis during space flight.
Another type of osteoporosis is a problem on Earth. As we grow older, the body begins to absorb bone much faster than it produces new bone. This leads to a lowered bone density, the same effect that microgravity has on astronauts. As a result, bones become more fragile and are more susceptible to fractures, especially in the hip, spine, and wrist. In many cases, people do not know that they have osteoporosis until their bones become so weak that an accidental bump or fall causes a fracture.
Just as astronauts eat a careful diet and get plenty of special exercise in space to prevent disuse osteoporosis, steps can be taken to prevent osteoporosis on Earth. A balanced diet rich in calcium and vitamin D, exercise, a lifestyle free of smoking and alcohol, bone density testing, and medication all prevent or alleviate osteoporosis.
Excerpted from Virtual Astronaut's Bag of Bones
A trip to Mars would likely take around eighteen months of flight. Even if there was enough gravitation on Mars for Recovery, it seems likely that the bone degradation of possibly 5% per month may continue for the entire eighteen month trip. >Would this mean that they might arrive at Mars after having sustained bone degradation of 48% to 90%? How long would the pioneers need to have their bones recover from such extreme weakness? The best they might hope for might be four and a half years of recovery on Mars, but since Mars has much weaker gravity (about 1/3 that of Earth), recovery might take even longer!
Could the pioneers on Mars do all the work at construction and farming and everything else, with such serious medical problems for at least the first few years of being on Mars? It seems nearly certainly impossible, where survival of an extended trip on Mars seems very unlikely.
NASA and others seem to be incredibly enthusiastic about sending a manned trip to Mars, but EVERYONE seems to agree that it would be a ONE WAY TRIP. That seems even more certain to be true with the Medical results described here. Why doesn't anyone see how incredibly grisly it is certain to be for Earth radio receivers to get daily messages about the Mars pioneers NOT being able to be strong enough to build any houses or grow any food, where everyone will realize that we will just be listening to a 'Death March' until all of them have died. And given that, the chance that there will EVER be a following space flight to Mars seems permanently out of the question.
People also imagine StarTrek style trips to even farther than Mars, and Medical effects of even longer trips like that seem even more certain to not survive.
People, including NASA, also optimistically claim that we will be building colonies on the Moon. But the Moon only has 1/6 the gravity on Earth and there seems a possibility that months of Microgravity on the Moon may cause the same bone degradation after some months. What if we come to learn that astronauts cannot survive more than six months or a year on the Moon?
Does NASA intend to do such minimal planning to discover these things only after we have a lot of stranded astronauts dying on Mars or in Moon colonies? Yes, it is a romantic idea to imagine that we have explorers in exciting adventures? But the ISS experiences seem to suggest that we humans are quite probably destined to only ever remain on our Earth.
On a related issue, a lot of allegedly intelligent people assume that the Universe is chock full of spaceships with aliens in them, traveling everywhere. They are nearly certainly totally wrong about that! It seems realistic that humanoid aliens might have similar Microgravity problems which we have experienced in the ISS, so such extended trips may be impossible for that reason. Robots, sure! In addition, we certainly know that humans generally need to be in an environment of around 1.0 G, and if high speed human space travelers intended to ever get up to a speed of half the speed of light (in order to get to the nearest possible planet near Proxima Centari during a 20 year trip) that spacecraft would have to continually be accelerating at around 2.0 G for half the trip and then decelerating at around 2.0 G for the second half. Occupants of that spacecraft would not have muscles and bones and blood vessels dealing with a 200-pound Earth weight but instead a 400-pound body during that twenty-year trip. It is hard to imagine how many serious Medical issues would arise among the 400-pound crew of the spaceship during those twenty years!
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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago