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As of this month, astronomers have discovered 5,506 exoplanets orbiting other stars. That number is growing daily, and astronomers are hoping, among other things, to find Earth-like worlds. But will we know one when we see it? How might we be able to tell an Earth-like garden from a Venus-like pressure cooker from upwards of 40 light years away? Is JWST up to the challenge?

In a paper released in preprint earlier this week, four researchers used a simulation to put the space telescope to the test. They found that there are indeed telltale signatures that should help us parse the exoVenuses from exoEarths – but there is a catch (we’ll come back to that).

This simulation worked like this: The researchers placed six Earth-like planets and six Venus-like planets 40 light years away, each with varying levels of carbon dioxide (CO2), cloud cover, and haze in their atmospheres. The simulated planets orbited around a star identical to TRAPPIST-1.

In the real world, TRAPPIST-1 is one of the most promising systems discovered so far in which astronomers hope to find an exoEarth. It features a dim red dwarf star (making observing its planets an easier task than it would be around a bright yellow star like our Sun). The system has seven rocky worlds, three or four of which might lie within the star’s habitable zone. JWST has already observed the innermost two planets, and found them to be barren rocks more akin to Mercury than to Earth or Venus.

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NASA/JPL-Caltech.

In the simulation, the orbits of the test planets were placed right on the ‘runaway greenhouse boundary’: the distance from the star where it’s possible for the same planetary catastrophe that turned Venus into a hellscape to occur.

The authors aimed a simulated JWST at the planets, matching the capabilities of the real telescope’s NIRCSpec instrument, which observes the wavelengths of light coming from distant worlds. Different compounds in the atmosphere show up as peaks, patterns, and spikes in the spectra, allowing researchers to see what chemical compounds are present.

But the data isn’t always clear-cut. Spectral signatures for some molecules hide the signatures of others, or mimic them, making it difficult to know for sure what we’re looking at.

“Venus-like clouds and hazes may prevent the detection of molecular species, or an atmosphere at all,” the authors write.

But that doesn’t mean impossible, and the model was intended to help determine what astronomers should be looking for. Here’s what they found:

First, if you want to determine whether a planet has an atmosphere at all, regardless of whether it is Earth-like or Venus-like, the best bet is to look for Carbon Dioxide (CO2). It has an easily detectible signal, and remains visible for both planets with clear skies and those with haze and clouds.

But CO2 is less useful for distinguishing between Earths and Venuses, because the signature of CO2 overlaps with both water and methane, confusing the data.

There is only one spectral feature that clearly shows up on a Venus-like planet and not on an Earth-like one: Sulfur Dioxide (SO2). SO2 reacts with water vapor, so if it is present, it would rule out a wet Earth-like planet and confirm a dry Venus-like one.

Here’s the catch. In the real world, Venus actually doesn’t have much SO2. UV radiation from the Sun has stripped it away.

But there’s still hope. Around a TRAPPIST-1-like red dwarf, SO2 would last much longer, making the detection of SO2 possible in that scenario.

“The reduced UV output from TRAPPIST-1 allows SO2 to have an extended lifetime in the exoVenus atmosphere, which enhances the possibility of the SO2 being detectable,” the authors claim.

As for an Earth-like planet, the best signature to look for is methane. There are absorption features of methane that don’t show up on Venus, and can be clearly distinguished from CO2. Furthermore, if methane is accompanied by oxygen, it may be evidence of life.

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Fly Slowly Through Enceladus’ Plumes to Detect Life

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Enceladus is blasting water into space from the jets at its southern pole. This makes it the ideal place to send a dedicated mission, flying the spacecraft through the plumes with life-detection instruments s. A new study suggests that a spacecraft must proceed carefully through the plumes, keeping its speed below 4.2 km/second (2,236 miles per hour). Using a specialized, custom-built aerosol impact spectrometer at these speeds will allow fragile amino acids to be captured by the spacecraft’s sample collector. Any faster, they’ll shatter, providing inclusive results.

One of the biggest surprises of the 20-year Cassini mission to the Saturn system was the discovery of the active geysers at Enceladus. At only about 500 km (310 miles) in diameter, the ice-covered Enceladus should be too small and too far from the Sun to be active. Instead, this little moon is one of the most geologically dynamic objects in the Solar System.

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Geysers spew from Enceladus in this image from the Cassini spacecraft. Credit: NASA/Cassini mission.

Cassini’s stunning backlit images of this moon show plumes erupting in Yellowstone-like geysers, emanating from tiger-stripe-shaped fractures in the moon’s surface. The discovery of the geysers took on more importance when Cassini later determined the plumes contained water ice and organics. Since life as we know it relies on water and a source of energy, this small but energetic moon has been added to the short list of possible places for life in our Solar System.

During three of Cassini’s passes of Enceladus in 2008 and 2009, the spacecraft’s Cosmic Dust Analyser measured the composition of freshly ejected plume grains. The icy particles hit the detector target at speeds of 6.5–17.5 km/s, and vaporized instantly. While electrical fields inside the instrument were able to separate the various constituents of the resulting impact cloud for analysis, for a future mission, scientists would like to measure the particles in the plumes without completely vaporizing them.

Back in 2012, researchers from the University of California San Diego started working on a custom-built unique aerosol impact spectrometer, designed to study collision dynamics of single aerosols and particles at high velocities. Although it wasn’t built specifically to study ice grain impacts, it turns out this instrument might be exactly what planetary scientists are looking for to use at Enceladus, or even at Jupiter’s moon Europa, where there is growing evidence of active plumes of water vapor erupting from its surface.

Robert Continetti’s one-of-a-kind aerosol impact spectrometer was used in this experiment. Ice grains impact the microchannel plate detector (far right) at hypervelocity speeds, which can then be characterized in-situ.

Continetti and several colleague have now tested the device in a laboratory, showing that amino acids transported in ice plumes — like at Enceladus — can survive impact speeds of up to 4.2 km/s. Their research is published in The Proceedings of the National Academy of Sciences (PNAS).

“This apparatus is the only one of its kind in the world that can select single particles and accelerate or decelerate them to chosen final velocities,” said Robert Continetti, a professor from UC San Diego, in a press release. “From several micron diameters down to hundreds of nanometers, in a variety of materials, we’re able to examine particle behavior, such as how they scatter or how their structures change upon impact.”

From Cassini’s measurements, scientists estimate the ice plumes at Enceladus blast out at approximately .4 km/s (800 miles per hour). A spacecraft would have to fly at the right speeds to make sure the particles could be captured intact.

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This composite image shows suspected plumes of water vapour erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The plumes, photographed by Hubble’s Imaging
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The International Space Station Celebrates 25 Years in Space

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NASA recently celebrated the 25th anniversary of the International Space Station (ISS) with a space-to-Earth call between the 7-person Expedition 70 crew and outgoing NASA Associate Administrator, Bob Cabana, and ISS Program Manager, Joel Montalbano. On December 6, 1998, the U.S.-built Unity module and the Russian-built Zarya module were mated in the Space Shuttle Endeavour cargo bay, as Endeavour was responsible for launching Unity into orbit that same day, with Zarya having waited in orbit after being launched on November 20 from Kazakhstan.

“I cannot believe it was 25 years ago today that we grappled Zarya and joined it with the Unity node,” said Cabana during the call from NASA Headquarters in Washington, D.C. “Absolutely amazing.”

While this milestone marks 25 years since the first two ISS modules were attached, it would be another two years until the ISS had a crew, Expedition 1, which arrived at the ISS in November 2000 and stayed until March 2001, beginning an uninterrupted human presence on the ISS that continues today. During the two-year period between the first mating and Expedition 1, the Russian-built Zvedza module was attached to the Unity and Zarya modules on July 26, 2000, after launching from Kazakhstan two weeks earlier. Assembly of the large modules of the ISS would continue until 2021 when the Roscosmos-funded Nauka module was attached in July 2021.

Now in its final configuration, the ISS is approximately the size of an American gridiron football field consisting of 8 solar arrays that provide the station’s power while maintaining an average altitude of 400 kilometers (250 miles). Its massive size consists of a pressurized module length along the major axis of 67 meters (218 feet), a truss (primary body) length of 94 meters (310 feet), a solar array length (measured along the truss) of 73 meters (239 feet), and a total mass of 419,725 kilograms (925,335 pounds).

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Artist rendition of the ISS compared to an American gridiron football field. (Credit: NASA)
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Image of the ISS taken by SpaceX Crew-2 mission on November 8, 2021 after it successfully undocked from the ISS Harmony module. (Credit: NASA)

Ever since the 3-person Expedition 1 crew first took command of the ISS, a total of 273 individuals from 21 countries have visited the orbiting laboratory and have been comprised of trained astronauts and private visitors. From most visitors to least, the following visitor countries include the United States, Russia, Japan, Canada, Italy, France, Germany, Saudi Arabia, United Arab Emirates, Belgium, Brazil, Denmark, Great Britain, Israel, Kazakhstan, Malaysia, Netherlands, South Africa, South Korea, Spain, and Sweden.

“One of my favorite aspects of the International Space Station is the international part of it,” said NASA Astronaut and Expedition 70 Flight Engineer, Jasmin Moghbeli, during the call. “We each bring our unique perspectives, not just from our different nationalities, but also our different backgrounds. I think we’re definitely strengthened by the international partnership. It’s just like gaining redundancy when you have multiple partners working together. It’s stronger and more resilient to any sort of problems or obstacles that come our way and so it definitely makes us stronger. And I think that’s why we have had the International Space Station up here for 25 years now.”

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Starship | Second Flight Test

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On November 18, 2023, Starship successfully lifted off at 7:02 a.m. CT from Starbase on its second integrated flight test.

While it didn’t happen in a lab or on a test stand, it was absolutely a test. What we did with this second flight will provide invaluable data to continue rapidly developing Starship.

The test achieved a number of major milestones, helping us improve Starship’s reliability as SpaceX seeks to make life multiplanetary. The team at Starbase is already working final preparations on the vehicles slated for use in Starship’s third flight test.

Congratulations to the entire SpaceX team on an exciting second flight test of Starship!

Follow us on X.com/SpaceX for continued updates on Starship’s progress

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