By learning about our home planet, we are preparing to deal with the great questions about our universe and about life itself. In fact, it’s not easy to get a good picture of our own galaxy, the Milky Way. The reason for that is simple: We are living inside it. Sitting in the middle of a forest it is hard to describe it properly. On the other hand, you can describe the nearby environment by sensing temperature and humidity and just by looking around. To get the big picture, we have to combine our experiences on earth with the view from above.
Seen from space, through eyes of satellites, the earth is a planet of oceans. More than 2/3 of the earth’s surface is covered by water. That doesn´t necessarily mean there´s a lot of water on earth. Our oceans are shallow and the deepest spot, the Mariana Trench, reaches only 11 km towards the center of our planet. There´s 6360 km left to go. The average ocean depth is around 4 km which is no more than 0,06% of the earth´s radius. Think of a huge globe, 3 m across. You could comfortably sleep in it, but the oceans, in scale, would be no deeper than one single millimeter! This thin fragile layer of moisture is crucial to life as we know it. In other words, we have to learn about our ocean life and continuously keep an eye on its wellbeing.
One important eye above us is ESA´s CryoSat. When the satellite was launched five years ago its mission was “just” to collect measurements for scientific research. Now CryoSat delivers maps over the Arctic sea-ice thickness, thanks to its onboard radar altimeter that penetrates clouds and darkness. Remember – a technical “eye” isn’t necessarily built to “see” the same way we humans do with our eyes. ICEYE is another “eye”, which will be monitoring polar ice. The ICEYE concept is based on a constellation of small satellites and will provide near-realtime ice information for the commercial shipping operators in the Arctic. Missions like these will increase our knowledge about the polar sea and ice areas and will also make operations in Arctic safer, more efficient and more environment-friendly.
Ambitious missions to learn about the origin of life as we know it are often connected to water. A related question is where the water on earth once came from. Rosetta mission to the comet 67P/Churyumov-Gerasimenko gave us our first information about water outside our planet and its atmosphere. Water isn´t “just water”. Depending on its origin, it has its unique signature. Read more about the water on 67P/C-G here.
Jupiters icy moon Europa may hide deep oceans of water under its smooth surface. As much as 2-3 times the quantity water on earth is expected to be found on a moon tinier than our own moon. That indicates an average “ocean”-depth of 9-13 km throughout the entire surface of Europa. Whether the water is frozen or liquid, due to a strong magnetic interaction with Jupiter and volcanic activity, is still to be found out.
It’s quite easy to understand why we want to monitor our home planet. But why do even the Americans go to Europa?
Now read this: Earth observations by satellite.
Jan teaches mathematics and interdisciplinary science to pupils 13-16 years of age at Sursik School, Pedersöre, Finland. Space-related science often gives some sort of answer to the question “Why?”, a question quite common in math class. It also triggers curiosity, one key component in progress.