December 6, 2021

I, Science

The science magazine of Imperial College

What parts of our solar system are realistically accessible?

NASA, Astronaut Michael Fossum

“Sooner or later, we must expand life beyond our little blue mud ball—or go extinct.” Elon Musk, founder of private spaceflight company SpaceX

Space travel and exploration has been described as the natural future for the human race by many throughout history, but when the furthest we have travelled is to our own moon, and with far less than one per cent of NASA’s highly trained and dedicated applicants selected for eventual spaceflight, are we a species really capable of leaving Mother Earth behind?

Although over 119 human years have been spent in space, that question is still being answered. The longest space mission to date was carried out by Valeri Polyakov, who spent 437 days aboard the space station Mir in 1995. He is a doctor specialising in space medicine and took part in the mission to demonstrate that humans can survive long enough periods in space to travel to Mars.

Whilst in space, his cognitive abilities and reactions were tested, and “an impressive stability of mood and performance were observed.” The only drops in his performance came in the days before and after take-off and for a few weeks after returning to Earth, which were put down to the extra stress on the brain from acclimatising to and from weightlessness.

Polyakov was not an ordinary man. He had already spent 240 days in space before this mission, and completed 19 years of training before that. The fact he climbed out of the Soyuz capsule unaided and walked the short distance to a nearby chair after landing was widely hailed as an amazing result, but that this was seen as something so remarkable shows the truth of the rigours even the best prepared human body undergoes during space travel.

In microgravity astronauts face major muscle and bone loss unless osteoporosis drugs and a large amount of exercise are taken. Blood pressure equalises throughout the body and so increases in the head, telling the body to produce less blood and causing the heart to atrophy. Recently, eyesight problems have been noticed in astronauts, leaving them farsighted, a major problem for people dealing with fine tools and instruments. Sleep deprivation is another concern for astronauts, causing many to have periods where they struggle to complete basic tasks and nod off midconversation.

It is being increasingly suggested that automated systems should be introduced to help monitor and aid these human errors. It seems that sometimes, far short of being the necessary, innovative and reliable parts of a space-mission, human participation causes many of the problems. So, if human space travel is limited, what about unmanned craft? How much of our galactic neighbourhood have our spacecraft succeeded in exploring?

The furthest object we have sent into space is Voyager One, which was widely hailed as entering interstellar space at the end of August last year after more than 35 years of travelling. This may seem relatively speedy, but strictly speaking the spacecraft is only thought to have left the heliosphere, which is the bubble of electrically charged particles that surrounds the sun, and is actually nowhere near leaving our solar system. Far outside of the heliosphere – another 200 to 300 years of Voyager’s travelling time away – stretches the Oort Cloud, a vast expanse of icy comets that may take Voyager over 30,000 years to emerge from the other side of. When it comes to exploring, we really are stuck within the confines of our solar system.

Even around the sun, our exploration is mostly limited to the closest planets. Mars is the most explored planet with 41 missions to study it so far attempted, and two currently en route. Over half of them have been failures. The successful ones have made their own records – NASA’s Opportunity rover has driven over 22 miles on Mars, the furthest any vehicle has driven on another planet. Mars is actually our second closest planet, but has always been fashionable to explore because of the hints of water having once flowed on its surface taunting us with the prospect of potential life. Venus is actually our closest planetary neighbour and is known to have a thick and inhospitable atmosphere that maintains incredibly high temperatures. The number of visits to planets further out is far lower. A flyby from Voyager Two is the only human contact that Neptune and Uranus have ever received, and Jupiter and Saturn have each been on the end of just four space missions.

Sometimes though, objects from the extremities of our solar system come to us. This November, Rosetta’s lander Philae will make the first ever controlled landing on a comet. Comets are chunks of dust and gas that littered the early solar system but were left out of planetary formation. They are the closest link we have to the original material of the nebula from which our sun and planets formed, and are thought to carry the complex organic molecules that may have kick-started life on Earth.

Rosetta is a European Space Agency project that left Earth in 2004 but, increasingly, the boldest future exploratory missions are being suggested by private companies. Mars One for example, promises to make history if its funding is reached and it puts a first wave of human colonists on Mars by 2025. Funds for the mission are being raised through private investment coordinated by for-profit company Interplanetary Media Group.

A whole host of other companies, including Planetary Resources Inc, plan to mine asteroids close to the Earth for a variety of resources from water to platinum. Commercial space projects like these, with business plans designed to attract investors, customers and press coverage are competing with traditional government-run space agencies like NASA that have to work within limited budgets.

It remains to be seen whether these more intrepid missions will get the funding they need. The main achievement of private company SpaceX, for example, has been to successfully reproduce relatively simple tasks such as getting safely in and out of the Earth’s orbit and sending unmanned spacecraft to the International Space Station.

Perhaps extensive promotion of the next innovative and publically accessible space mission, like the reality TV show that Mars One is proposing to help select its final colonisation candidates, will enable the required funding to be raised. Or perhaps the true limit to our space adventures will come down to something far less prosaic than the top speed of our rockets or the limits of human endurance.


IMAGE: Wikicommons