Image of Space Biology infographic

Infographic: Space biology

Our universe in a nutshell? In this infographic, we try to get to grips with some astronomical numbers

This infographic originally appeared on pages 2 and 3 of ‘Big Picture: Space Biology’. You can download a copy of the standalone infographic at the bottom of this page.

Putting this diagram together, we found that different sources gave different numbers for the same thing. Why don’t they match? Well, data can be interpreted in different ways, and estimates can be made using different methods and different baseline data. Definitions matter, too – different sources might define ‘size’ or ‘orbit’ differently. Which should you choose? The source itself is important – is it from a primary or a secondary source? Is it reliable? Is it recent? Is it from an organisation with an agenda or from an impartial source? 

Here, we have provided you some background information on which data we used and why. We also have included some discussion questions – you may like to discuss these as a group or think about them as part of an individual activity.

Radiation doses

Measurements from NASA’s Mars rover Curiosity estimate that the radiation dose an astronaut would be exposed to on a six-month return trip to Mars is about 1.01 sieverts, according to Sieverts are the SI unit for radiation absorption and are the equivalent to joules per kilogram.

  • Is this a lot? To get a sense of whether this is true, we compared it to some of the other figures, such as these from the United States Nuclear Regulatory Commission. Their chart shows the radiation doses that humans might receive in their everyday lives. These figures are in millirems, so we converted to sieverts in order to compare.
  • It’s also worth keeping in mind that the figures the chart gives could change over time. For example, a regulatory limit in 2014 might be lower than one in 2015. An older X-ray machine might give a higher dose of radiation to a patient than a more recent machine. 
  • Figures could also vary based on location. What’s an everyday dose for someone who lives near Chernobyl in Ukraine? How does that compare to someone who lives in the middle of a large city like London, or a small village in Yorkshire?
  • Can you think of other ways these figures might change?
  • Are you comfortable with the veracity of the figure? It has been reported by, so we are referencing a secondary source. Can you find the primary source?

Human space explorers

According to Wikipedia, 536 people from 38 countries have gone into space as of November 2013. So why didn’t we just say that?

Well, there are different definitions of going into space, we learned. There are the Fédération Aéronautique Internationale (FAI) guidelines on space flight, and there are the US Department of Defense classifications. There are sub-orbital flights, Earth orbit, beyond Earth orbit, walking on another planet or moon. Some of those 536 only completed a sub-orbital flight, but most reached Earth orbit.

In the small space of an infographic, it can be difficult to deliver all of that information. We have to make a judgement call, and ultimately we decided that just knowing that there were more than 500 people who had travelled to space was enough to give a sense of the numbers. But that number, is of course, climbing every year.

  • Were you surprised by the number? Did you think it was more or less than approximately 500?
  • What do you think the gender breakdown was? Or the nationality?
  • We mention the youngest (25) and oldest (77) space explorers. Can you do a little research to find out who they are?

The cost of launching into orbit

According to NASAs Advanced Space Transportation Program fact sheet, the cost of putting 1 pound (lb) of payload into space is $10,000.

For our infographic, we converted pounds to kilograms (1 lb = 0.45 kg).

We also converted US dollars into UK pounds, which is where things get a little tricker. The exchange rate is constantly changing; even on the day you read this the exchange range may have gone up or down by a few pence or cents, depending on your perspective. We chose to use the exchange rate on the day we created the infographic as a single point in time. We also decided that we would round the figures, preferring to be approximate than to claim a precision that might not be completely accurate.

The other point to consider is whether that cost has come down since NASA published its fact sheet. In it, the agency commits to reducing the cost to hundreds of dollars per pound within 25 years and tens of dollars per pound within 40 years. We contacted them to see if they have made any progress on the cost, but we did not get a response. (If we do, we will add it here.)

  • Were you surprised by the cost?
  • We chose these examples (a laptop, a pug, a pound coin, a bag of sugar, a Smart car) as representatives. Would you have used different ones? What would they have been?
  • Is space exploration worth the cost? For more, see our article for discussion.

Searching for Earth’s twin

Speculation continues over where else in the universe life could exists, and it often centres around finding other planetary bodies that are similar to Earth. Astrobiologists sometimes use the Earth Similarity Index (ESI) to identify which planetary bodies are most similar to Earth. 

The ESI produces a value between 0 and 1 based on a planetary body’s radius, overall density, escape velocity and surface temperature. Earth, understandably, scores a 1 on the scale. Anything between 0.8 and 1 is considered Earth-like.

Most of the planets in our solar system are not Earth-like; the closest is Mars, as you can see from the graphic.

The exoplanets with Kepler names, which you may have seen in the news, have been highlighted for their similarity to Earth. Kepler 238.B has an ESI of 0.89 and Kepler 62.E is 0.83. But before you pack your bags, take note of just how far away they are from Earth: 4,700 light years and 11,900 light years, respectively. Getting there could prove difficult, particularly given that the furthest that humans have ever travelled is 400,171 km, which is the far side of the Moon (which, incidentally, has an ESI of 0.56).

Distance is an important point in this graphic, too; when researching the distances from Earth to other places, we found they change, often dramatically, depending on where they are in their orbit around the Sun. For planets in our solar system, we chose the distances at which they were closest to Earth; for the moons of Saturn and Jupiter, we used the planets as a proxy. 

  • Do you think which distance we chose makes a big difference? What about when you consider those distances in relation to how far the Kepler exoplanets are?
  • Looking at the graphic, which planet do you think humans could travel to and live?
  • Have a look online at the ESI of other planetary bodies. How about Europa, Jupiter’s moon which may have liquid water under its surface? Where would it fit?

Firsts in space

This section of the infographic is less complex, though nonetheless an interesting read. If you would like to know more about the history of humans and other animals in space, read our ‘Animal Astronauts’ article.

Were any of these dates surprising?



Lead image:

‘Big Picture: Space Biology’ (2015) CC BY

Downloadable resources

About this resource

This resource was first published in ‘Space Biology’ in June 2015.

Cell biology, Statistics and maths, Ecology and environment, History, Health, infection and disease
Space Biology
Education levels:
16–19, Continuing professional development