During the 1960s, the first robotic explorers began making flybys of Venus, including the Soviet Venera 1 and the Mariner 2 probes. These missions dispelled the popular myth that Venus was shrouded by dense rain clouds and had a tropical environment. Instead, these and subsequent missions revealed an extremely dense atmosphere predominantly composed of carbon dioxide. The few Venera landers that made it to the surface also confirmed that Venus is the hottest planet in the Solar System, with average temperatures of 464 °C (867 °F).
These findings drew attention to anthropogenic climate change and the possibility that something similar could happen on Earth. In a recent study, a team of astronomers from the University of Geneva (UNIGE) created the world’s first simulation of the entire greenhouse process that can turn a temperate planet suitable for Life into a hellish, hostile one. Their findings revealed that on Earth, a global average temperature rise of just a few tens of degrees (coupled with a slight rise in the Sun’s luminosity) would be sufficient to initiate this phenomenon and render our planet uninhabitable.
One big question about Earth’s formation is, where did all the water come from? New data from the James Webb Space Telescope (JWST) shows newly forming planets in a system 370 light-years away are surrounded by water vapor in their orbits. Although astronomers have detected water vapor in protoplanetary disks before, this is the first time it’s been seen where the planets are forming.
Tell me this montage shouldn’t be hanging in the Lourve Museum. Every time I think I’ve seen the “best image” of Rosetta’s comet, another one takes its place. Or in this case four! When you and I look at a comet in our telescopes or binoculars, we’re seeing mostly the coma, the bright, fluffy head of the comet composed of dust and gas ejected by the tiny, completely invisible, icy nucleus.
As we examine this beautiful set of photos, we’re privileged to see the individual fountains of gas and dust that leave the comet to create the coma. Much of the outgassing comes from the narrow neck region between the two lobes.
All were taken between February 25-27 at distances around 50-62 miles (80 to 100 km) from the center of Comet 67P/Churyumov-Gerasimenko. Looking more closely, the comet nucleus appears to be “glowing” with a thin layer of dust and gas suspended above the surface. In the lower left Feb. 27 image, a prominent streak is visible. While this might be a cosmic ray zap, its texture hints that it could also be a dust particle captured during the time exposure. Because it moved a significant distance across the frame, the possible comet chunk may be relatively close to the spacecraft. Just a hunch.
While most of Rosetta’s NAVCAM images are taken for navigation purposes, these images were obtained to provide context in support of observations performed at the same time with the Alice ultraviolet (UV) imaging spectrograph on Rosetta. Observing in ultraviolet light, Alice determines the composition of material in coma, the nucleus and where they interface. Alice will also monitor the production rates of familiar molecules like H2O, CO (carbon monoxide) and CO2 as they leave the nucleus and enter 67P’s coma and tail.
From data collected so far, the Alice team has discovered that the comet is unusually dark in the ultraviolet, and that its surface shows no large water-ice patches. Water however has been detected as vapor leaving the comet as it’s warmed by the Sun. The amount varies as the nucleus rotates, but the last published measurements put the average loss rate at 1 liter (34 ounces) per second with a maximum of 5 liters per second. Vapors from sublimating carbon monoxide and carbon dioxide ice have also been detected. Sometimes one or another will dominate over water, but overall, water remains the key volatile material outgassed in the greatest quantity.
That and dust. In fact, 67P is giving off about twice as much dust as gas. We see the comet’s dual emissions by reflected sunlight, but because there’s so much less material in the jets than what makes up the nucleus, they’re fainter and require longer exposures and special processing to bring out without seriously overexposing the comet’s core.
67P’s coma will only grow thicker and more intense as it approaches perihelion on August 13.
In an encouraging find for habitability researchers, astronomers have detected molecules on the smallest planet ever — a Neptune-sized planet about 120 light-years from Earth. The team behind the discovery says this means the dream of understanding the atmospheres on planets even closer to size of Earth is getting closer.
“The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules,” stated co-author Heather Knutson, of the California Institute of Technology.
This particular world is not life-friendly as we understand it, however. Called HAT-P-11b, it’s not only a gas giant but also a planet that orbits extremely close to its star — making one circle every five days. And unusually among planets of its size that were previously probed by astronomers, it appears to have clear skies.
The team examined the world using the Hubble Space Telescope’s Wide Field Camera 3, looking at the planet as it passed across the face of its star. The team compared the signature of elements observed when the planet was in front of the star and when it was not, and discovered telltale signs of water vapor in its atmosphere.
While other planets outside our solar system are known to have water vapor, the ones previously examined are much larger. Jupiter-sized planets are much easier to examine not only because they are larger, but their atmospheres puff up more (making them more visible from Earth.)
To confirm the water vapor was not a false signal from sunspots on the parent star (which also can contain it), the team used the Kepler and Spitzer space telescopes to confirm the information. (Kepler’s single field of view around the constellation Cygnus, which it had been peering at for about four years, happily included the zone where HAT-P-11b was orbiting.) The infrared information from Spitzer and the visible-light data from Kepler both showed the sunspots were too hot for water vapor.
Further, the discovery shows there were no clouds in the way of the observations — a first for planets of that size. The team also hopes that super-Earths could have clear skies, allowing astronomers to analyze their atmospheres.
“When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” stated lead author Jonathan Fraine, of the University of Maryland, College Park. “In this case, we found clear skies on a distant planet. That’s lucky for us because it means clouds didn’t block our view of water molecules.”