Mars History: Exploration

Fueled by the fictions in popular culture and scientific speculation, curiosity led to the direct exploration of the Red Planet using robotic spacecraft.  Beginning in 1960 with a series of mostly unsuccessful Soviet flyby probes, our exploration of Mars, though fraught with failures, challenges and high costs, has slowly resulted in an accumulation of important scientific discoveries. As a result, we’ve begun to find some answers to questions about water and life on Mars, with each mission bringing us one step closer to the reality of sending humans to Mars.

Artist’s Rendering: Mariner 4 Spacecraft (Image: NASA)

NASA Mariners: 1962-1973
Although the initial Mariner missions failed, missions 4 through 10 provided several groundbreaking firsts in space exploration. Launched in 1964, Mariner 4, NASA’s first successful Mars flyby provided the first close-up images of a planet other than Earth, and its 22 photos revealed a cratered surface.

Mariners 6 and 7, identical spacecraft launched in 1969, were flyby missions with onboard computers capable of transmitting images 2000 times faster than the Mariner 4. They acquired 201 far-range and close-up images of Mars, which effectively disproved the existence of artificial canals on the surface. Experiments detected atmospheric constituents, temperature and surface pressure data.

Launched in 1971, Mariner 9 dramatically altered what we knew about Mars, providing 54 billion pieces of data, including 7329 images of the planet’s surface and the first high resolution photos of the two Mars moons. Although it was delayed on arrival by dust storms, Mariner 9 showed incredible surface variations, including ancient river beds – feasible evidence of historic water.

Viking 1 orbiter (Image: NASA)

Russian Probes: 1969-1973
Although Mars 2 crashed into the Mars surface and Mars 3 only worked for 20 seconds after landing, these Russian probes were the first human artifacts to land on the Red Planet. Of seven flyby, lander and orbiter spacecraft in the series, Mars 5 (1973) succeeded, sending back 60 images of the Martian terrain and information on the temperature, altitude, ozone layer, magnetic field and ionosphere.

 Upcoming planned (or proposed) missions

  • 2007: Phoenix – NASA scout lander
  • 2009: Phobos-Grunt – Russian Federal Space Agency surveyor
  • 2009: Mars Science Lab – NASA rover
  • 2009: Beagle 2: Evolution – European Space Agency lander
  • 2011: ExoMars – European Space Agency rover
  • 2011: 2011 – NASA scout
  • 2011: Mars Science and Telecommunications Orbiter – NASA orbiter
  • (2016: Astrobiology Field Lab – NASA rover)
  • 2016: Mars Sample Return Mission – European Space Agency and NASA mission.

NASA Viking Orbiter/Landers: 1975-1982
Launched separately in 1975, Viking 1 and 2 went into Mars orbit in 1976, first imaging the entire surface for viable landing sites, before the landers detached from the orbiters to successfully touch down. The Viking landers provided 1400 images of the Mars surface around the two landing sites, analyzed surface samples for signs of life, studied the atmosphere and measured seismic waves. The first spacecraft to transmit colour panoramic images of the Martian terrain, the Viking spacecraft provided extensive scientific information, including evidence of historic surface water and data on seasonal dust storms, pressure changes and atmospheric gases. Biological experiments, however, showed no signs of life.

NASA Mars Global Surveyor: 1996-present
Launched in 1996 to recover the mission objectives of the failed Mars Observer, the Mars Global Surveyor mapped the topography of the Martian surface, providing high resolution images and vast amounts of data on gravity, weather, climate, atmosphere and the magnetic field. Its detailed photos of topographical features such as gullies suggested the presence of frozen water. Still in use as a data relay long after it’s mission timeline, the Mars Global Surveyor went into an error condition on November 2, 2006.

NASA Mars Pathfinder: 1996-1998
Launched in 1996, the Pathfinder lander arrived on Mars in 1997, releasing the first Mars rover, the Sojourner, to explore the Martian surface and provide data on the feasibility of low-cost landings. This mission proved the viability of a number of new technologies, including airbag landings, and was able to operate under a much smaller budget than previous missions. It also gained widespread public attention. In addition to more than 17,000  images, the mission’s analysis of the Martian atmosphere, climate, geology, rocks and soil provided further evidence of the Red Planet’s watery past. Contact was lost with the lander and rover in late 1997.

Artist’s rendering: Mars Express
(Courtesy NASA/JPL-Caltech)

NASA Mars Odyssey
Originally planned as an orbiter/lander, the Mars Odyssey was launched as an orbiter-only mission in 2001 to analyze Martian mineral, climate and geological data and study radiation hazards. It served as a communications relay and source of information on atmospheric conditions for other missions such as the Mars Reconnaissance Orbiter, and its mission had been extended through 1998 for further observation of seasonal changes in polar ice, clouds and dust storms.

European Space Agency Mars Express
Although contact with its lander, the Beagle 2 was lost, the Mars Express Orbiter, launched in 2003 to obtain high resolution imagery for geological analysis and conduct mineralogical and atmospheric mapping, has discovered the presence of hydrated sulphates, silicates and rock-forming minerals on Mars. In addition to detecting methane in the atmosphere, suggesting volcanic or hydrothermal activity or perhaps even the presence of subsurface microorganisms, it discovered buried impact craters and confirmed the presence of underground water-ice.

Artist’s rendering: Airbags used to land Spirit and Opportunity safely on Mars (Courtesy NASA/JPL-Caltech)

NASA Mars Exploration Rovers (MER)
Spirit and Opportunity, the two Mars Exploration rovers launched in 2003 have analyzed Martian rocks and soil in the search for geological clues and measurable data about water on Mars, as well as information about future landing sites. Equipped with advanced instrumentation, including cameras for panoramic photos, navigation and hazard-avoidance, as well as X-ray spectometers, the rovers have provided evidence of historic water, including rock stratification and the distribution of chlorine and bromine along what must have been a former salty sea. The mission has been extended through to September 2007.

NASA Mars Reconnaissance Orbiter
Designed to orbit Mars for more than a Martian year, the Mars Reconnaissance Orbiter was launched in 2005 and has been in orbit since spring 2006. This multifunction spacecraft is gathering data on Martian landforms, weather and surface conditions with six advanced technologies, including a high resolution imager. In addition to collecting information on possible landing sites, the orbiter is testing an improved telecommunications system that will become a relay station for future missions.

The Mars Curse:
Despite these achievements, to date almost half of Mars missions have failed, a phenomenon Time magazine journalist Donald Neff described as the Mars Curse. Although this has fueled some far-fetched speculations, including one involving a galactic probe-eating ghoul, scientists have conducted detailed investigations as to why each mission failed.

Mission Name Mission type Date How it failed
Marsnik 1 and 2 (aka Mars 1960A/1960B) Flybys 1960 Launch failure.
Sputnik 22 Flyby 1962 Broke up in Earth orbit.
Mars 1 Flyby 1962 Contact lost.
Sputnik 24 Lander 1962 Broke up during transfer to Mars trajectory.
Mariner 3 Flyby 1964 Protective shield failed; solar batteries died.
Zond 2 Flyby 1964 Contact lost.
Mars 1969A and Mars 1969B Orbiters 1969 Launch failure.
Mariner 8 Flyby 1971 Launch failure.
Cosmos 419 Orbiter/lander 1971 Bad ignition timer setting.
Mars 7 Lander 1973 Lander separated early and missed the planet.
Phobos 1 Orbiter/lander 1988 Software error resulted in deactivation of solar paneled thrusters; batteries died.
Mars Observer Orbiter 1992 Contact lost.
Mars 96 Orbiter/lander 1996 Failed in Mars trajectory; re-entered Earth’s atmosphere.
Nozomi Orbiter 1998 Mars orbit insertion burn failed; flew past Mars.
Mars Climate Orbiter Orbiter 1998 Destroyed due to navigation error during Mars orbit insertion.
Mars Polar Lander Lander 1999 Contact lost.
Deep Space 2 (DS2) Penetrators 1999 Unknown: contact lost after landing.
Beagle 2 (part of Mars Express) Lander 2003 Contact lost.


Mars in the Solar System

Relative Size of Planets and the Sun

How much do you know about Mars and its role in the solar system? Take this short quiz to find out.

Mars in the Solar System Quickie Quiz:

Mars is considered:

A) a major planet in the solar system
B) a dwarf planet in the solar system
C) the smallest planet in the solar system
D) an inferior planet in the solar system

A: Mars is one of the major planets in the solar system.  The dwarf planets are small bodies that are still big enough to hold a spherical shape. These include 1 Ceres, 90482 Orcus, 28978 Ixion, among others. Pluto was downgraded to a dwarf planet in August 2006.

Mars is part of:

A) The inferior planets
B) Zone 1, the inner planets
C) Zone 2, the outer planets
D) Zone 3, the outer solar system

B: The inner planets are within the solar system’s asteroid belt and include Mercury, Venus, Earth and Mars. The rest of the major planets are outer planets. Mercury and Venus, which lie within Earth’s orbit, are inferior planets.

Mars is the only planet that:

A) is part of the Kuiper Belt.
B) is close enough to be explored by Earth probes.
C) has a name with Germanic, not Greco-Roman origins
D) has a vast quantity of iron oxide on its surface

D: Pluto is part of the Kuiper Belt, a ring of ice thought to be the origin of comets. Space probes from earth have already explored Saturn, Mercury, Jupiter, Venus, Uranus and Neptune, as well as Mars. Earth is a Germanic name, although it is known in many languages as Terra after the Roman goddess. The vast quantity of iron oxide on the surface of Mars is what gives the Red Planet its fiery colour.

Mars is different from the Earth in that it has:

A) no history of volcanic activity
B) no polar ice caps, ice and snow
C) no seasonal temperature changes
D) lower atmospheric pressure

D: Earth and Mars both have volcanoes, seasonal temperature changes, polar ice caps, ice and snow (although the “snow” on Mars is different from that on Earth). But the Red Planet has much less-dense an atmosphere than the Earth.  Wind-storms on Mars can kick up huge dust-storms, but the wind doesn’t have much force behind it due to the low atmospheric pressure.

4. Mars is most similar to:

A) Venus
B) Jupiter
C) Earth
D) Saturn

C: While Venus is the closest planet to the Earth in both proximity and size, it is also closer to the Sun, and therefore incredibly hot and inhospitable. Although it has a thin atmosphere, Mars is the planet considered most similar to Earth, particularly in its rocky terrain, relatively small size and potential to sustain some form of life. Scientists believe Mars was even more like Earth early in its history.

Quick Comparison:

Stats Mars Earth
Place in the solar system 4th planet from sun 3rd planet from sun
Distance from the sun 227 940 000 km

1.52 (astronomical unit)

146 000 000

1 au

Size: diameter 6 779 km 12,745.591 km
(by volume)
95.3% carbon dioxide
2.7% nitrogen
1.6% argon
0.13% oxygen
traces of water vapour, neon, krypton and xenon
77 % nitrogen
21 % oxygen
1 % argon
0.038% carbon dioxide
traces of water vapor, neon, methane, krypton, hydrogen, nitrous oxide and ozone.
Surface air pressure Average of about 7 millibars 1013 millibars at sea-level
Surface gravity 3.71  metres squared 9.80 metres squared
Surface bulge Tharsis: a bulge 4000 km across and 10 km high Equatorial bulge: 43 km across the equator
Day length (sidereal day) 24 hours, 39 minutes and 35.25 seconds 23 hours, 56 minutes and 4 seconds
Year length 669.6 Martian solar days (about 1.9 Earth years) 365.2 mean solar days
Global average temp -55 degrees C
(-133 to 27 degrees)
14 degrees C
(-88 to 58 degrees)
Largest canyon Valles Marineris: 4000 km long, 5.3 km deep and 20 km wide Mariana Trench in the Pacific Ocean: 2550 km wide −10.9 km deep and 69 km wide
Escape velocity 5.03 km a second 11.19 km a second
Global magnetic field? No Yes
Moon(s) Two: Phobos and Deimos One: the moon


Mars History: Why this is a hard thing to do?

The failure rate of Mars Missions is high. Many things can go wrong, and the smallest overlooked detail can result in disaster. In 1998, a miscalculation as a result of a mix up of metric and standard measurement units cost NASA its Mars Surveyor Climate Orbiter. The most common cause of failure has been lost communications.

These failures can be very expensive. Billions of dollars have been spent on Mars exploration, triggering some to question whether or not the scientific payoff of space programs is worth their funding and support from tax dollars.

But recent, successful missions such as Mars Pathfinder, the Mars Exploration Rovers and the ESA’s Mars Express have garnered worldwide attention and interest. New discoveries providing evidence that Mars was once a watery planet, perhaps more like Earth, together with the looming possibility that forms of life could exist on the Red Planet have fueled the impetus to further explore this distant frontier.

A human mission, such as that depicted in the Race to Mars mini-series, is even more complex.  Not only does the mission need to bring supplies and fuel for a return-trip, as well as launching living quarters, vehicles and equipment…but the cost of failure is incredibly high in human terms, economic terms, and for the very future of the space-program.

 The Mars Curse and the Galactic Ghoul

Because of the high rate of failure in reaching and landing on the Red Planet, some have suggested, although often in jest, that there is a Mars Curse plaguing missions to Mars. Time Magazine journalist Donald Neff imagined that the curse is a result of the Galactic Ghoul, a fictional space monster that consumes Mars probes.

By the numbers
Number of successful Mars missions
1960-2005: 14
Number of failed Mars missions
1960-2005: 27

Failed missions to Mars
1960: Marsnik 1. Flyby. Launch failure.
1960: Marsnik 2. Flyby. Launch failure.
1962: Sputnik 22. Flyby. Broke up in Earth’s atmosphere.
1962: Mars 1. Flyby. Contact lost.
1962: Sputnik 24. Lander. Broke up en route to Mars.
1964: Mariner 3. Flyby. Mechanical failure. Lost in orbit.
1964: Zond 2.  Mars flyby. Contact lost.
1969: Mars 1969A. Orbiter. Launch failure. 1969: Mars 1969B. Orbiter. Launch failure.

1971: Mariner 8. Orbiter. Launch failure.
1971: Cosmos 419. Obiter/lander. Failed en route.
1971: Mars 2. Orbiter/lander. Failed en route.
1971: Mars 3. Orbiter/lander. Contact lost after landing.
1973: Mars 4. Flyby. Failed to slow and flew past Mars orbit.
1973: Mars 6. Lander. Contact lost.
1973: Mars 7. Lander.  Landing probe separated early, missed planet.

1988: Phobos 1. Orbiter/lander. Contact lost.
1988: Phobos 2. Orbiter/lander. Contact lost.

1992: Mars Observer. Orbiter. Contact lost.
1996: Mars 96. Orbiter/lander. Trajectory failed. Broke up in Earth’s atmosphere.
1998: Nozomi . Orbiter. Into orbit then failure. Abandoned in space.
1998: Mars Climate Orbiter. Navigation error. Destroyed in Mars atmosphere.
1999: Mars Polar Lander. Contact lost.
1999: Deep Space 2. Penetrators. Contact lost after landing.

2003: Mars Express. Orbiter and lander. Contact lost with Beagle 2 lander.

The following discussion uses the Race to Mars mission-plan as an example.

What can go wrong:


  • Possible equipment or systems failure, including guidance system, seals or valves, rocket boosters can cause crashes, gas leaks and explosions.
  • Structural failure can break up the rocket.
  • Decompression can suffocate the crew

36-48 hours into flight:

  • Docking with the crew transit vehicle. This is a slow and methodical process. Dangers include possible collision and pressure failure.  If computerized process fails, a manual override is available, but risky.
  • Ship spun up to provide Artificial gravity to protect astronauts’ health. Spining too fast would make the crew sick and cause structural damage to the ship.

2-5 months, traveling to Mars

  • Elevated radiation from a solar flare could harm crew and damage electronics.
  • Loss of communication (here or at any other phase of the mission): would make the mission much more difficult, with the crew reliant on their own skills and equipment
  • Astronauts could be harmed by cosmic radiation and excess carbon dioxide in the air.
  • Puncture from a micrometeorite could cause partial decompression.

5 months, arriving in orbit

  • Critical navigation moment. No margin for error.
  • Astronauts must transfer to the MADV lander already orbiting Mars. Docking is always dangerous.

Landing on Mars

  • Known as the most dangerous 6 minutes in the mission.  Everything from parachutes to retro rockets to LIDAR equipment to Terminal Descent Engines must work precisely in order to slow the lander down. Any variation in the timing or function and the lander can end up kilometers out of place.  And with the vehicles, supplies and surface-habitat already in position on Mars, ending up too far off course could compromise the mission.

On Mars: 60 days

  • Astronauts are under threat from dust devils (static-electrical discharge), Martian dust storms (poor visibility, long duration) and radiation (a risk due to the thin protective atmosphere of Mars). If their space suits malfunction or rip, depressurization and extreme cold can cause loss of limbs or death.

Ascent from Mars

  • The ascent from Mars and docking with the crew transit vehicle again requires split-second timing.

Leaving Mars and re-entry

  • The return trip is as risky as the initial journey. Re-entry once the crew reach Earth is always dangerous.

Mars History: Famous Astronomers and Mars Discovery

Astronomer Tycho Brahe

BC: The Mythologized Mars

Visible as the red planet in the night sky, Mars was recognized by Ancient Babylonians as an aggressive force. They called Mars Nergal, the star of death, and on its day (Tuesday) performed ceremonies to ward off this planet’s hostile influences.

While Ancient Egyptians called Mars Har Decher, the Red One, and the Greeks named it Ares after their god of war, Mars got its moniker from the Romans. In Roman mythology, Mars was a mighty warrior, the god of spring who ushered in the season of empire-expanding battle.

1500s: Eyeball observations and radical theories

Nicolaus Copernicus (1473-1543) presented the blasphemous theory that the planets in the solar system orbit around the sun instead of the earth. Prior to the invention of the telescope, Danish astronomer Tycho Brahe (1546-1601) calculated the position of Mars.

1600s: A difficult time for science

Johannes Kepler (1571-1630), a student of Tycho Brahe, proposed that Mars had an elliptical orbit. Galileo Galilei (1564-1642), who was tried in the Inquisition for subscribing to Copernicus’ controversial theory, observed Mars with a primitive telescope. Dutch astronomer Christiaan Huygens (1629-1696) studied Mars with a more advanced telescope, observing the planet’s south pole and speculating about Martian life.

One of Schiaperelli’s maps of Mars (1888)

1700s: Research data begins

Continued improvements in telescope design allowed astronomers, such as Brit Sir William Herschel (1738-1822) to make important, and surprisingly accurate observations of the Red Planet, including that of its axial tilt (estimated then at 30 degrees; now thought to be 25.19 degrees), the position of its poles and its thin atmosphere.

1800s: The Canal Craze

Milan astronomer Giovanni Schiaperelli (1835-1910) created early maps of Mars, naming more than 300 landscape features he viewed through his telescope. In 1877, his announcement of the existence of Martian  “caneli,” or channels in Italian, was misinterpreted by English-speakers, who believed he had discovered alien-made canals.

1900s: Martians invade pop culture

American Percival Lowell (1855-1916) wrote that the canals on Mars were artificially-made and promoted the belief in life forms on the Red Planet. Although this idea was questioned by other scientists, who showed canals to be an illusion, Martians and alien folklore permeated 20th century pop culture. Beginning in the 1960s, with flyby missions, the US and Russia spent billions studying Mars and trying to land space probes on the Red Planet, which proved to be very difficult.]. In 1976 two NASA Viking probes showed Mars to be a dry, uninhabitable planet. In 1996 NASA published evidence for ancient microscopic life on Mars, a claim later discounted by some of the same scientists.

Mars Phoenix Lander (Courtesy Nasa/LMSS)

2000s: The exploration of Mars

NASA’s Mars Odyssey conducted the a large-scale geological survey of Mars, beginning in 2001. In 2002, data from Odyssey showed evidence of vast ice beneath the surface of Mars. The European Space Agency’s Mars Express set off in 2003 with its Mars Express Orbiter and Beagle Lander. Although contact with the lander was lost, the orbiter confirmed the presence of ice on Mars. NASA’s Mars Exploration Rovers, launched in 2003 and 2004, began a long geological survey of the planet, relaying evidence that the planet was once drenched in water. NASA launched a two-year science study in 2005 with its Mars Reconnaissance Orbiter. Its Phoenix Mars Lander (2007), subsequent rover missions (2009-2011), Russia’s Phobos-Grunt probe (2009) and Europe’s ExoMars (2011) will provide valuable data in preparation for the first human mission to Mars.

Known effects of long-term space flights on the human body

Although space travel looks easy on TV and in the movies, in reality it causes both short term and long term health problems for a spacecraft’s most delicate cargo: its crew. On Earth, gravity is a force our bodies have to work against, which keeps our cells, bones and muscles strong. Remove the force of gravity from the equation and over the duration of a long-term micro-gravity space flight, human bodies undergo dramatic changes. That’s why some experts feel artificial gravity will be necessary for the crew whenever possible during the Mars mission. Artificial gravity at even partial Earth-normal would help reduce the severity of some of the space-related health problems, and helps ensure the crew will arrive on Mars fit enough to carry out their duties there.

Yet even if the crew of the Mars mission has access to artificial gravity-conditions for at least part of their journey, they will still have to deal with many of the physiological changes that occur in space. Consider the following effects of long-term space flights on the human body and then ask yourself: would you apply to be part of a Mars-bound crew?

Short term:

Blood circulation

On Earth, the cardiovascular system circulates fluids through the body, working against gravity to prevent blood from pooling in the legs and bringing blood to the brain. In microgravity the cardiovascular system doesn’t work as hard, triggering a fluid shift. As fluids move up from the lower body to the trunk, the heart rate increases and blood pressure rises. Astronauts experience puffy faces, headaches, nasal congestion and skinny “bird” legs as a result.

Space sickness

Almost 40 percent of astronauts experience a form of motion sickness in space. Along with nausea and vomiting, symptoms include headaches, malaise and dizziness. Caused in part by the blood circulation changes described above, symptoms of space sickness usually subside within two or three days as astronauts adapt.

Changes in red blood cells

Some evidence suggests that microgravity causes astronauts’ red blood cells to change. The red blood cells appear to change shape in space, becoming more spherical, and fewer cells populate bone marrow. Cells do return to normal once back under Earth-normal gravity, however, even after a long-term mission.

Compromised immune system

Studies conducted in space and in test missions in Antarctica show that isolation and sleep deprivation may result in a weakened T-lymphocyte system, causing compromised immunity. Astronauts are more prone to infection by common and latent viruses as well as microorganisms such as bacteria and fungi. They may also experience increased allergy symptoms. Since the immune system doesn’t adapt under these conditions, the Mars crew will need to bring antiviral drugs and other medicines. Modern drugs degrade after six months though, so it is likely that the drugs’ active ingredients will have to be packed separately and be mixed on board as needed.

Back aches

No longer compressed by the force of gravity, back vertebrae separate slightly and astronauts grow up to two inches taller in space. A side-effect of added height, besides shorter pants, is back aches, which scientists believe are caused by the relaxation of back muscles and ligaments. Once astronauts return to Earth, they shrink back to their former height.

Muscle loss

Without gravity, everything in space floats. There’s no need for astronauts to walk, stand or lift in microgravity, and their muscles, particularly in their legs, atrophy. Underused, flabby leg muscles affect balance, posture and strength, and can increase the risk of tendonitis and fat accumulation. To counter these effects, which also occur to a lesser degree in artificial gravity, and to ensure otherwise sedentary astronauts will be strong and limber upon arrival to Mars, the crew will have to exercise up to two hours a day. After returning to Earth, they will undergo an extensive training program to re-strengthen their muscles.


Constant noise and irregular light patterns make it difficult to sleep on board a spacecraft. Astronauts may experience fewer hours of regular sleep and/or poor quality sleep. Combine that with the disruptions of our natural Earth day/night cycles en route and the longer Mars day (by 39 minutes) and the result is stressed and fatigued astronauts. During NASA’s Mars Exploration Rover Mission (2003), scientists and engineers working as mission control crews who lived on Mars time on Earth reported the circadian rhythm shift to be both disruptive and tiring.

Lack of cleanliness

Water is carefully conserved in space because the crew must carry all of their supplies with them on the long journey to Mars, and space (more precisely, mass) is at a premium on such a mission. This makes keeping clean a challenge. Mars-bound astronauts will have moist towelettes for daily scrubbing, but they’ll only be able to shower infrequently. Experienced astronauts say they create a wider buffer of personal space to keep out of odour range of their crew mates.

Poor balance and orientation

It takes time for the human brain to adjust to new points of reference in space. Astronauts in microgravity usually lose their sense of direction and feel uncoordinated or clumsy. Because inner ear and muscular sensors seek terrestrial clues, astronauts must learn to rely on visual cues for balance and orientation. But even visual cues can be confusing – astronauts in microgravity need to adjust to the fact that up and down don’t really matter in space like they do on Earth. Artificial gravity during space travel would definitely help with balance and orientation.

Psychological effects

Astronauts are generally resilient when it comes to stress, but there’s no question that spending more than a year in space will be psychologically difficult. Long-term isolation, monotony, limited mobility and living in close quarters with other astronauts could lead to depression, interpersonal conflicts, anxiety, insomnia and even psychosis. While astronauts on previous missions say they took comfort in the view of Earth, Mars astronauts will watch the Earth getting progressively smaller and farther away, which could intensify feelings of isolation.

Re-adjusting to Earth

Astronauts returning to Earth risk low blood pressure. A sudden reintroduction of gravity makes the blood in astronauts’ bodies rush down, resulting in dizziness and lightheadedness. Tiny muscles in veins that send blood uphill may have atrophied and can fail to push blood up to the heart. Astronauts may lose consciousness or be unable to remain standing. Low blood pressure is more severe after long missions – Mir cosmonauts had to be carried off their landing craft by stretcher. To help their bodies readjust on re-entry, astronauts can drink salt water to increase the volume of fluids in their bodies, wear G-suits (rubberized full body suits which are inflated to squeeze the extremities) or potentially use new drugs to increase blood pressure.

Long term:

Bone loss

Weightlessness triggers the human body to excrete calcium and phosphorus (in urine and feces), resulting in rapid bone loss. In the time it takes to get to Mars and back, a crew member’s bone density loss will be equivalent to that of a lifetime on Earth. Like osteoporosis on Earth, bone loss in space can lead to fractures, weakness and painful urinary stones. The most dramatic changes occur in the heel bone, femoral neck, lumbar spine and pelvis. Exercise in space and upon return can help slow the loss, but it will take two years or more of dedicated, consistent training upon return to repair it.  Artificial gravity would also serve to mitigate this problem is it is part of the mission design.

Cellular organization

Recent research implies that gravity helps cells create patterns. In microgravity, the microtubules in developing cells might not organize the same way they would on Earth, even after the astronauts return. It is unknown how this will affect the Mars crew over the long term.


Astronauts in space experience flashes of light that seem to appear behind their eyelids. What’s actually happening is that galactic cosmic rays are slashing through their brains – retinal flashes are merely a physiological marker. Along with solar flares, these rapidly traveling rays expose astronauts to high levels of ionizing radiation. This form of radiation can damage atoms in human cells, leading to decreased immunity and a higher risk of cataracts, cancer, heart disease, damage to the central nervous system and brain damage. Long-term exposure to ionizing radiation in open space is a significant concern for the crew of the Mars mission. A number of solutions are being explored to help protect astronauts, including antioxidant-rich foods, such as blueberries and strawberries and close monitoring of radiation levels combined with the use of radiation shields.