Europa, one of Jupiter's four largest moons, has an ocean
lurking underneath its ice shell. The ocean's presence has been speculated
based on Europa's surface features including rift zones, ice ridges, and chaos
regions (Fig. 1). Plumes on Europa are significant because of Europa's potential to harbor life in its ocean. Europa's ice shell is potentially tens of kilometers thick, making drilling to its ocean nearly impossible. These eruptions may deposit material from Europa's interior onto its surface where it can be more readily studied by a fly-by mission or lander mission. Thanks to the
Hubble Telescope, Europan plumes have now been imaged.
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| Figure 1. Cross section of Europa's ice shell and subsurface ocean. In the background are Jupiter and Io, one of the most active bodies in the solar system. The plumes eject material from the surface ocean, but how the plumes are activated remains a mystery. From left to right, surface features include plumes, rifts and chaotic terrain. Image Credit: NASA JPL/ Caltech |
In 2012, scientists at the Southwest Research Institute discovered water vapor signatures coming from Europa. The signatures are likely plumes due to cyrovolcanism (ice volcanoes). More recently, Hubble was used again to directly image plumes erupting from Europa (Fig. 2). Out of ten observations, the plumes were spotted three times. Since Enceladus experiences eruptions during certain points in it orbit, one hypothesis is that Europa would experience a similar eruption cycle. Initial investigations suggest this may not be the case.
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| Figure 2. Image of Plumes with high-res image of Europa superimposed. Image Credit: NASA/ESA |
The locations of Enceladus' plumes tend to cluster in the southern hemisphere, near the tiger-striped patterns. Europa's plumes originally clustered near the southern pole, but the recent observations showed the plumes may originate closer to the equator. The timing of the eruptions was compared to Europa's orbital position relative to Jupiter, and indicated that the eruptions do not always occur at the predicted times. This has lead several studies to suggest that plumes may not be controlled by tides, or Europa's orbit, but may be caused by internal convection in the subsurface ocean. Until more observations can be made, the eruptions on Europa remain unpredictable.
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| Figure 3. Artists illustration of plumes on Europa's surface. Jupiter can be seen rising in the background. Image Credit: NASA JPL/ CalTech |
This is a good effort and generally accessible, but you bring in a lot of scientific terms that need explaining to reach the widest audience. The illustrations are great, but the objects you wish to highlight are uncertain.
ReplyDeleteMake sure to use the pointer. What is tidal resonance? Why is the plume so far out from the moon? What is the size of the moon. What is the period of the eruptions? What drives convection in the sub-surface ocean? Good projection and cadence of voice? Are there any indication of organic molecules in the plumes?
ReplyDeleteGood job simplifying your talk so non-planetary people can understand it. You note at the end that the geysers are 100km high. It might be useful the reader if you note this sooner. As soon as I saw your image of the geyser with the superimposed photo of Europa, I found myself asking the size of these geysers. Also, I might have missed this but what is the composition of material that is being ejected? How do we know?
ReplyDeleteWhat's a chaotic terrain? You mention it in the caption but I didn't catch the exact definition.
ReplyDeleteIs it reasonable to assume that it's impractical to drill a borehole on the order of 10s of km on Europa? Terrestrial limitations to borehole depth are due to latent heat in the crust melting boreheads, but it seems like that wouldn't be as much of an issue for icy Europa. That's my two cents, anyway. I like your article :) It makes me Jovial... get it. Jupiter.
ReplyDeleteI think you used the word tidal several times in the talk before defining it as gravitational pulling by planets. A non-scientist might think this has to do with going to the beach/surfing. A discussion of tidal forces also doesn't appear until the end of the blog post. Perhaps bump this up a bit? Isn't this the whole reason why there is liquid water?
ReplyDeleteBut overall a really good talk that was very easy to follow!
DeleteThe final image is cool. I'm wondering what is the size of the plume because the eruptions look huge from figure 2. Does the water become ice immediately after eruption? I'm assuming the surface temperature of Europa is much cooler than Earth.
ReplyDeleteI agree that you use more scientific terms in this post than you need to. Otherwise I thought you presented well today - you perhaps spoke a little fast.
ReplyDeleteWhat is Enceladus? You mention it, but don't define it. I agree with everyone else that this would be a difficult concept for the general public to understand the way you presented it.
ReplyDeleteAs everyone else has mentioned, fewer scientific terms would make both the article and talk much more approachable to the general public. I think as part of this, simplifying the discussion of these plumes would help. The general public isn't necessarily going to be thrilled by an in-depth discussion of the different models for their eruption. I also think in the article, there needs to be a definition of what exactly these plumes are (in laymen's terms) at the very beginning. As it is, they just get brought up at some point, and then explained in terms of cryovolcanism later on. You do a good job of framing the importance of sampling/understanding Europa's oceans, and how plumes can help us with that.
ReplyDeleteDiagram 1 is a bit too small. Possibly resize the image. I will not restate others points. But I would like to address what was not stated: why do we care, or why are we discussing this? Its interesting certainly, but there is a missing connection of why you are telling people about it. One way to start would be discuss that a new (or planned) NASA mission will be conducted, then use that to discuss why it is being conducted in the first place. Just a thought.
ReplyDeleteI like your presentation. You used more scientific terms in your blog than in your presentation. The images are really cool.
ReplyDeleteI like the detail in your writing. Your post is inspiring because you mentioned the link to finding life, our previous advancements (Hubble) and our future technologies (Europa lander). I think it might be good to break down some of these terms to make the reading simpler, like 'chaos regions' and/or 'internal convection in the subsurface'
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