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The Making of Juice – Episode 10.3
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
What Would It Take to Say We Found Life?
We call this the podium test. What would it take for you personally to confidently stand up in front of an international audience and make that claim? When you put it in that way, I think for a lot of scientists, the bar is really high.
So of course, there would be obvious things, you know, a very clear signature of technology or a skeleton or something like that. But we think that a lot of the evidence that we might encounter first will be much more subtle. For example, chemical signs of life that have to be detected above a background of abiotic chemistry. And really, what we see might depend a lot on where we look.
On Mars, for example, the long history of exploration there gives us a lot of context for what we might find. But we’re potentially talking about samples that are billions of years old in those cases, and on Earth, those kinds of samples, the evidence of life is often degraded and difficult to detect.
On the ocean worlds of our outer solar system, so places like Jupiter’s moon Europa and Saturn’s moon Enceladus, there’s the tantalizing possibility of extant life, meaning life that’s still alive. But potentially we’re talking about exceedingly small amounts of samples that would have to be analyzed with a relatively limited amount of instrumentation that can be carried from Earth billions of miles away.
And then for exoplanets, these are planets beyond our own solar system. Really, what we’re looking for there are very large magnitude signs of life that can be detectable through a telescope from many light-years away. So changes like the oxygenation of Earth’s atmosphere or changes in surface color.
So any one of those things, if they rose to the suspicion of being evidence of life, would be really heavily scrutinized in a very sort of specific and custom way to that particular observation. But I think there are also some general principles that we can follow. And the first is just: Are we sure we’re seeing what we think we’re seeing? Many of these environments are not very well known to us, and so we need to convince ourselves that we’re actually seeing a clear signal that represents what we think it represents.
Carl Sagan once said, “Life is the hypothesis of last resort,” meaning that we ought to work hard for such a claim to rule out alternative possibilities. So what are those possibilities? One is contamination. The spacecraft and the instruments that we use to look for evidence of life are built in an environment, Earth, that is full of life. And so we need to convince ourselves that what we’re seeing is not evidence of our own life, but evidence of indigenous life.
If that’s the case, we should ask, should life of the type we’re seeing live there? And finally, we need to ask, is there any other way than life to make that thing, any of the possible abiotic processes that we know and even the ones that we don’t know? And as you can imagine, that will be quite a challenge.
Once we have a piece of evidence in hand that we really do think represents evidence of life, now we can begin to develop hypotheses. For example, do we have separate independent lines of evidence that corroborate what we’ve seen and increase our confidence of life?
Ultimately, all of this has to be looked at hard by the entire scientific community, and in that sense, I think the really operative word in our question is we. What does it take to say we found evidence of life? Because really, the answer, I think, depends on the full scientific community scrutinizing and skepticizing this observation to finally say that we scientists, we as a community and we as humanity found life.
[END VIDEO TRANSCRIPT]
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Last Updated Sep 10, 2025 Related Terms
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By European Space Agency
The European Space Agency’s Jupiter Icy Moons Explorer (Juice) is on track for its gravity-assist flyby at Venus on 31 August, following the successful resolution of a spacecraft communication anomaly that temporarily severed contact with Earth.
The issue, which emerged during a routine ground station pass on 16 July, temporarily disrupted Juice’s ability to transmit information about its health and status (telemetry).
Thanks to swift and coordinated action by the teams at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, and Juice’s manufacturer, Airbus, communication was restored in time to prepare for the upcoming planetary encounter.
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By European Space Agency
When the European Space Agency’s Jupiter Icy Moons Explorer (Juice) flew past our Moon in August 2024, its Radar for Icy Moon Exploration (RIME) instrument listened to radio wave echoes to reveal the height of the lunar surface.
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By Space Force
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
How do we do research in zero gravity?
Actually when astronauts do experiments on the International Space Station, for instance, to environment on organisms, that environment is actually technically called microgravity. That is, things feel weightless, but we’re still under the influence of Earth’s gravity.
Now, the very microgravity that we’re trying to study up there can make experiments actually really kind of difficult for a bunch of different reasons.
First of all, stuff floats. So losing things in the ISS is a very real possibility. For example,
there was a set of tomatoes that was harvested in 2022 put it in a bag and it floated away and we couldn’t find it for eight months.
So to prevent this kind of thing from happening, we use a lot of different methods, such as using enclosed experiment spaces like glove boxes and glove bags. We use a lot of Velcro to stick stuff to.
Another issue is bubbles in liquids. So, on Earth, bubbles float up, in space they don’t float up, they’ll interfere with optical measurements or stop up your microfluidics. So space experiment equipment often includes contraptions for stopping or blocking or trapping bubbles.
A third issue is convection. So on Earth, gravity drives a process of gas mixing called convection and that helps circulate air. But without that in microgravity we worry about some of our experimental organisms and whether they’re going to get the fresh air that they need. So we might do things like adding a fan to their habitat, or if we can’t, we’ll take their habitat and put it somewhere where there might already be a fan on the ISS or in a corridor where we think they are going to be a lot of astronauts moving around and circulating the air.
Yet another issue is the fact that a lot of the laboratory instruments we use on Earth are not designed for microgravity. So to ensure that gravity doesn’t play a factor in how they work, we might do experiments on the ground where we turn them on their side or upside down, or rotate them on a rotisserie to make sure that they keep working.
So, as you can tell, for every experiment that we do on the International Space Station, there’s a whole team of scientists on the ground that has spent years developing the experiment design. And so I guess the answer to how we do research in microgravity is with a lot of practice and preparation.
[END VIDEO TRANSCRIPT]
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Last Updated May 28, 2025 Related Terms
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