PRE2019 1 Group2
- Group -
- Kasper Dols - 0953689
- Marco Luijten - 1008931
- Wouter Meekes - 1011988
Main tutor: Tijn Borghuis
Mission to Europa
Introduction
Europa is a very interesting, mysterious moon of Jupiter, discovered by Galileo Galilei in the year 1610. The moon raised a lot of interest in the past couple of decades, because there are some indications of liquid water on the moon. Since water is at the top of the list of ingredients that make life possible, the speculations for extraterrestrial life on Europa began to rise. Water dissolves nutrients for organisms to eat, transports important chemicals within living cells and allow those cells to get rid of waste. [1] But due to the circumstances at Europa, the water is believed to be hidden underneath a thick coat of ice. This coat is estimated to be 10 kilometers around the whole moon, with a deviation of 160. [2] Calculations will be performed using this 10 km; the 160 m deviation will be considered negligible with respect to 10 km.
Presence of liquid water on the surface
But can there be water present in liquid form somewhere at the surface of Europa? Probably not. One of the reasons to assume this, is based on the phase diagram of water, shown to the right. As can be seen in the image, the lowest pressure at which water can still exist in liquid form is its triple point at 611.73 Pa (0.0061 atm), at the usual temperature of 273.15 K (0 °C). Below that pressure, water has no liquid form. Since the pressure at Europa’s surface is about 10-10 atm, this means that liquid water can not stably exist on the surface of Europa. Some water may come to surface for a brief moment, but will almost instantaneously either freeze or boil, leaving no water remaining. It should be noted that indeed this diagram does not extend below 10-5 atm, and that based on this image it is thus technically not possible to say that water does not have a liquid form at such ultra-low pressures. However, it is first of all unlikely that such an out-of-place phase change exists based on this and other phase diagrams. Secondly, this ‘liquid’ may not be liquid as we know it and still be unable to support life. Much like solid water has different crystalline structures at different temperatures and pressures, so can this liquid water have very different properties based on the environment it is in. Hence based purely on physical grounds it is unlikely that liquid water in a familiar form exists on the surface of Europa. [3]