'Riding a fireball through atmosphere': How Artemis II astronauts will return to Earth
The Orion spacecraft will fall over 120,000 metres in 13 minutes and travel to a special "splashdown" site off the coast of California.
After a record-breaking week in space, the four astronauts on NASA’s 10-day lunar flyby Artemis II mission are getting ready for the most intense part of their journey: the return to Earth.
In 13 minutes, the Orion spacecraft will fall over 400,000 feet (121 kilometres) and travel almost 2,000 miles (3,218 kilometres) over the Pacific Ocean to a special "splashdown" site off the coast of California.
For almost half of this time, their communication with NASA's ground crew will be cut off entirely, and they will endure temperatures up to 2,760 degrees Celsius.
Astronaut Victor Glover said he’s been thinking about this re-entry from the Artemis II mission since the day he was selected over three years ago.
He described re-entry as "riding a fireball through the atmosphere" in a press conference on Wednesday.
Here’s a closer look at what the astronauts are doing right now to prepare for their fiery arrival back to Earth, and what comes after.
Preparing for descent
To get ready for re-entry, the crew has already carried out a return trajectory correction manoeuvre, a small engine burn to adjust the spacecraft’s trajectory for a more precise route back to Earth, according to Rick Henfling, the director of Artemis II’s entry flight.
The astronauts also tested suits that help them combat orthostatic intolerance, a condition that makes it difficult for astronauts to maintain blood pressure and blood flow when standing up after returning from space.
On the ninth day of the 10-day flyby, the crew will manually drive the vehicle to centre the Earth in one of the windows and then fly it to an altitude where the tail of the ship points towards the sun, so it can generate more power, Henfling added.
Then, on Artemis II’s tenth day, the astronauts get ready for the final descent.
About 20 minutes before re-entry, the service module that supported and powered the crew during the mission will separate from Orion. It will eventually burn up in the atmosphere before coming down to Earth on its own.
Then, the crew is ready for a last "raise burn," a final opportunity to change the flight path before their descent, which starts southeast of Hawaii and will eventually see them land off the coast of California, Henfling said.
The crew then lowers their visors to cover their eyes and will be "in an isolated environment in their launch and entry suit" until they reach the Earth’s surface.
How will they perform the re-entry?
The capsule will re-enter the Earth's atmosphere at about 400,000 feet (121,920 metres) and will have to travel 1,950 miles (3,138 kilometres) to its landing site.
"That’s where the fun really begins," Henfling said.
Only 24 seconds after entering the Earth’s atmosphere, Orion will hit a "blackout," when plasma builds up around the spacecraft, which will cut the communications between the astronauts and NASA control for about six minutes.
Orion has the world’s largest heat shield on its body, which will protect the astronauts from the extreme heat and plasma.
After the six-minute blackout is over, Orion will be at an altitude of 150,000 feet (45,720 metres), travelling at a "very quick" speed towards the landing site, so the next focus will be on deploying parachutes, Henfling said.
Two small drogue parachutes — designed for deployment from a rapidly moving object — that are seven metres in diameter will unfurl at an altitude of 25,000 feet (7,620 metres) to slow Orion down to 494 km/h. Three larger parachutes will slow Orion down even further to 38 km/h, the speed it will maintain to splash down into the Pacific Ocean.
Once the craft is in the water, a system of five orange airbags will inflate around the top of the spacecraft and will flip it into an upright position, so the crew can get out.
The re-entry will take 13 minutes from start to finish, Henfling said. "It's going to start quickly, and it's going to be over even faster," he added.
The Artemis II is scheduled to splash down off the coast of San Diego on Friday 10 April at approximately 8:07 p.m. EDT (2:07 a.m. CEST), according to NASA
NASA has some "contingency" trajectories, where the crew could be landing further away than planned, based on any problems that might come up during descent, Henfling said.
What happens after the mission?
Liliana Villarreal, the Artemis landing and recovery director, is leading a team to sea aboard the USS John P. Murtha, a transport dock ship that will be used to recover the astronauts after their landing.
The ship, along with small boats, will be stationed "at a safe distance" away from Orion's landing place. After a quick assessment of the air and water around the capsule, the boats will open the Orion hatch and help the astronauts out into an inflatable raft called the "Front Porch," Villarreal said.
The astronauts wait on the "Front Porch" for two helicopters to come and bring them to medical facilities, where they receive immediate medical checkups.
"We expect to recover the crew and deliver them to the medical bay within two hours of splashdown," Villarreal said. "We had a very successful recovery […] during the Artemis I mission, and we feel confident during our testing and training […] Artemis II will be just as successful."
The Orion capsule will be loaded onto the USS John P. Murtha and will return to the closest Navy base within 24 hours after splashdown.
The capsule then undergoes some quick inspections, but it will quickly be loaded onto a truck and driven back to NASA in Florida.
Washington (United States) (AFP) – While the Artemis II astronauts have been protected from the icy vacuum of space on their journey, their bodies have nonetheless been left exposed to possibly high levels of radiation -- a danger of space travel that NASA is anxiously waiting to study.
Issued on: 10/04/2026 - RFI
Their trip around the Moon has taken the four astronauts farther into space than any human before -- more than 1,000 times the distance from Earth to the International Space Station.
Earth's magnetosphere offers some protection against radioactive cosmic rays and solar particles to the orbiting ISS, but no such cover on the Moon.
Studying the impacts of radiation is essential as NASA hopes to eventually build a Moon base and send astronauts on the long trip to Mars.
The US space agency installed radiation sensors on the Orion capsule and took blood samples of the astronauts before takeoff to compare with samples post-trip. The crew's saliva samples are gathered throughout the journey and their health is monitored via smartwatches.
NASA has also placed state-of-the-art computer chips in the capsule that can replicate certain physiological functions, like that of an organ.
Mission planners chose to mimic bone marrow, which produces blood cells and is one of the tissues "most quickly affected by radiation and other stressors," NASA Human Research Program chief scientist Steven Platts told AFP.
With all of the data, Platts said his team hoped to better understand the variation between low earth orbit and deep space.
"It will be good research information for us to see the level of radiation, but also the type of radiation," he said.
"Our prediction is that we'll see a lot more galactic cosmic radiation... which is from supernovas and is everywhere," versus radiation coming from the Sun, he said.
Mental health
Platts said while most people associate radiation with cancer risk, it also can impact the central nervous system and blood circulation.
"It can lead to inflammation in the brain, and that's one of the things that can increase the risk of Parkinson's disease," he said.
With the Artemis II astronauts spending just 10 days in space, radiation is not a major concern, but the danger could rise dramatically with longer stays on the Moon.
Extensive health studies were conducted on the Apollo astronauts, but technology has advanced greatly in the 50 years since, said Bruce Betts, chief scientist at the Planetary Society, a space advocacy group.
"There will be a lot of information on the medical side of things," he said.
The other major focus is on psychological risks of spending long periods of time on the Moon or Mars.
With greater disconnection from home and tight living quarters, mental health could pose the greatest danger to astronauts on such missions, Platts said.
He compared the difference between the ISS and the tiny Orion capsule as like going from a "six-bedroom house, like a mansion... to a camper van."
© 2026 AFP
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April 10, 2026
By Eurasia Review
The absence of a signal could itself be a signal. This is the idea behind a new study published in the Journal of Cosmology and Astroparticle Physics (JCAP), which aims to redefine how we search for dark matter, showing that it may not be necessary to find the same “clues” everywhere in order to interpret it.
In particular, the study suggests that even if we observe a certain type of signal at the center of our galaxy — an excess of gamma radiation that could result from the annihilation of dark matter particles — failing to detect the same signal in other systems, such as dwarf galaxies, is not enough to rule out this explanation.
Dark matter, in fact, may not consist of a single particle, but of multiple slightly different components, whose behavior varies depending on the cosmic environment.
The galactic center gamma-ray excess
Dark matter: we know it exists and is abundant, but we have never observed it directly and therefore we still do not know what it is. For decades, it has been a major focus for cosmologists and astrophysicists trying to understand its nature. Its presence is inferred mainly from the gravitational effects it exerts on visible matter, but so far none of the proposed hypotheses has received definitive confirmation from data. The search therefore continues.
Many leading dark matter models describe it as being made of particles. In some of these scenarios, when two particles meet, they can annihilate, producing high-energy radiation such as gamma rays, which astronomers attempt to detect.
“Right now there seems to be an excess of photons coming from an approximately spherical region surrounding the disk of the Milky Way,” explains Gordan Krnjaic, a theoretical physicist at the Fermi National Accelerator Laboratory (Fermilab) in the United States and one of the study’s authors. This excess of gamma-ray photons observed by the Fermi Gamma-ray Space Telescope could be due to dark matter annihilation. However, there are also alternative explanations, in which the gamma-ray emission would be produced by astrophysical sources such as a population of pulsars.
To resolve this question, it is necessary to look elsewhere. “If certain theories of dark matter are true, we should see it in every galaxy, for example in every dwarf galaxy,” explains Krnjaic.
Dwarf galaxies
Dwarf galaxies are very small and faint systems, but extremely rich in dark matter. They have very little astrophysical background — fewer stars and less ordinary radiation — and therefore represent ideal environments in which to search for “clean” signals.
Standard theories that describe dark matter as made of particles generally predict two possibilities for how these particles annihilate. In the simplest case, the annihilation probability is constant and does not depend on the particles’ velocity: in this scenario, if we observe a signal at the center of our galaxy, we should also expect to see it in other dark matter–rich systems, such as dwarf galaxies.
In the second case, the annihilation probability depends on the velocity of the particles. Since dark matter particles in galaxies move at very low velocities, this type of interaction makes annihilation extremely rare, and therefore the signal effectively invisible everywhere.
Within this framework, the absence of a signal in dwarf galaxies would make it difficult to interpret the excess of gamma radiation observed at the center of our galaxy as being due to dark matter.
Krnjaic and collaborators, however, describe an alternative, more complex scenario that could explain the absence of a signal in dwarf galaxies while still maintaining the interpretation of the signal observed in the Milky Way as a possible effect of dark matter.
Two different particles
“What we’re trying to point out in this paper is that you could have a different kind of environmental dependence, even if the annihilation probability is constant in the center of the galaxy,” explains Krnjaic. “Dark matter could straightforwardly be two different particles, and the two different particles need to find each other in order to annihilate.”
The probability that the two components of dark matter meet and annihilate would also depend on the ratio between these two particles within each astrophysical system. This ratio could be different in galaxies like our own — where the two types of particles might be present in similar proportions — and in dwarf galaxies, where it could instead be strongly unbalanced.
“In this way, you get very different predictions for the emission,” explains Krnjaic.
The model proposed by Krnjaic and colleagues therefore represents a more flexible alternative to the simplest standard scenario, as it allows for the possibility of explaining the absence of a gamma-ray signal in dwarf galaxies without ruling out a dark matter origin for the signal observed in the Milky Way.
In the future, the Fermi Gamma-ray Telescope may provide more precise data on dwarf galaxies — currently still limited — helping to clarify whether these systems emit gamma radiation or not. In principle, the observation of a signal would be compatible with a similar distribution of the two components also in dwarf galaxies, while its absence could suggest that one of the two is less abundant. However, this interpretation is not unique and depends on additional astrophysical factors, making it necessary to compare the model with a wider range of observations.
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