Fireball over California thought to have been caused by part of Chinese spacecraft re-entering atmosphere.

Witnesses across California between San Diego and Sacramento, as well as the Las Vegas in Nevada, have reported observing a bright fireball meteor at about 1.40 am local time (8.40 am GMT) on Tuesday 2 April 2024. The fireball is described as having moved from southwest to northeast, over the central part of the state. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry, as is believed to have been the case on this occasion.

The 2 April 2024 Fireball seen from Ontario, California. American Meteor Society.

The fireball is thought to have been caused by a part of a Chinese spacecraft which launched on 29 November 2022 re-entering the atmosphere. The Shenzhou 15 spacecraft caried three taikonauts (the Chinese equivalent of astronauts) to the Tiangong Space Station. The taikonauts returned to Earth on 3 June 2023 aboard the Shenzhou 15 re-entry module, the only portion of the craft designed to re-enter the atmosphere safely. The remaining portion of the spacecraft has been on a decaying orbit since this time, finally re-entering the atmosphere this week.

The portions of a Shenzhou spacecraft. Ilya Kharlamov/Wikimedia Commons.

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China successfully lands probe on Mars.

The China National Space Administration has successfully landed a probe on Utopia Planitia, a vast lava plain in Mars' northern hemisphere. The lander comprises the Zhurong Rover, a six wheeled mobile vehicle armed with an array of instruments, plus a supporting platform with a radio transmitter enabling it to communicate with the orbiting Tianwen-1 spacecraft, and thence to Earth. The successful landing makes China only the second nation to have landed a probe on Mars, with the United States having completed several successful landings, but several attempts by the Russian and European space agencies having failed.

 

An artist's impression of the Zhurong Rover surveying the surface of Mars. Aerospace China/China National Space Administration/Wikimedia Commons.

The Tianwen-1 mission was launched from the Wenchang Spacecraft Launch Site on 23 July 2020, and entered orbit around Mars on 24 February 2021, with the probe setting down on Utopia Planitia at 7.18 am on Saturday 15 May 2021, Beijing time (11.18 pm on Friday 14 May, GMT). The Zhurong Rover is equipped with seven kinds of scientific instruments: two remote-sensing cameras, the Mars-Orbiting Subsurface Exploration Radar, the Mars Mineralogy Spectrometer, the Mars Magnetometer, the Mars Ion and Neutral Particle Analyzer and the Mars Energetic Particle Analyzer.

 

An animation shows how the Zhurong Rover touched down. BBC.

The name 'Zhurong' (祝融) was chosen by a popular online vote from a list of ten candidate names. It is the name of a fire god traditionally worshiped in southern China, which ties in with the Chinese name for the planet Mars, Huoxing (火星), meaning 'Fire Planet'.

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Part of Chinese rocket falls into the Indian Ocean to the west of the Maldives.

Part of a Chinese Long March 5B heavy-lift launch vehicle has fallen into the Indian Ocean to the west of the Maldives. The rocket, which was used to launch the Tianhe Module of the new Chinese Space Station on Thursday 29 April 2021, but entered an unstable elliptical orbit after the launch, leading to concerns that it might fall to Earth on a populated area of Europe, the Middle East, or South Asia. In the event it re-entered the Earth's atmosphere over the Arabian Peninsula early on Sunday 9 May 2021, with much of the spacecraft's mass being burned up in the atmosphere, and the remainder falling into the ocean to the west of the Maldives.

 

Part of the Chinese Space Station being launched on 29 April 2021. Po Xiaoxu/Xinhua/AP/Picture Alliance.

The uncontrolled re-entry of the rocket booster has attracted criticism from space technology experts in Europe and the US, who have raised concern about the rising number of Chinse rocket portions falling to Earth. In May 2020 two parts of a Chinese launch vehicle fell off the coast of Mauritania and on the village of Mahounou in Côte d'Ivoire, in July 2019 part of another booster re-entered the atmosphere over Florida, but is thought to have completely burned up before hitting the ground, and in November 2016 part of a launcher fell onto a jade mine in Myanmar, although nobody was injured in any of these incidents.

The parts of a Long March 5b rocket. Xinhua/China Daily/BBC.

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Part of Russian spacecraft found on beach in Bahamas.

A spherical metal tank, believed to have come from a Russian spacecraft, has been found on a beach in the Bahamas. The object, a spherical metal ball, was found projecting from the white sand of a beach on Harbour Island on Wednesday 24 February, by British woman Manon Clarke, who was walking on the beach with her family. The ball bears an inscription in Russian which states that has an operating temperature range of between -170°C and -190°C, and capacity of 43 litres, a maximum weight of 41 kg, and was manufactured in 1998. This is typical of a hydrazine propellant tank, typically used in unmanned spacecraft, with Mark Morabito of Virgin Galactic, stating that he is 99% certain that this is what the object is.

 

A titanium tank with a Russian inscription found on a beach in the Bahamas this week. Manon Clarke/The Independent.

Spacecraft tend to contain a lot of thick-walled spherical tanks, which is the most stable shape for a tank containing liquids under pressure in a changing gravity field. Unfortunately this is also a good shape for surviving re-entry into the Earth's atmosphere, so as the amount of space junk orbiting the Earth increases, so does the number of metal spheres falling from the sky. As yet there have been no reported cases of death or serious injury caused by space junk, but it does seem to be an increasing hazard on Earth as well as in orbit, with several reports of damage to property now coming in each year.

 

The basic design of a hydrazine bladder tank, thought to be the type object found on a Bahamas beach this week. The tank comprises a tough, protective, outer shell, typically made of titanium, with a flexible bladder inside, which shrinks as the gas inside is expelled, maintaining a constant pressure. Ariane Orbital Propulsion Centre.

Exactly how the tank came to be on a beach in the Bahamas is less clear. No falling debris (which would resemble a meteorite to people on the ground) has been observed in the Bahamas recently, although it could have fallen at night and not been seen, or buried by the sand on the beach for several years. Alternatively, it could have fallen in the sea somewhere in the Atlantic or Caribbean and simply floated to its current position. Sarah Hudspith of the University of Leeds has suggested that it may have originated from Cuba, a Cold War ally of the Soviet Union, although the manufacture date, 1998, several years after the break up of the Soviet Union, would seem to make this less likely.

 

Local residents excavating a metal object found on a beach in the Bahamas this week. Manon Clarke/The Independent.

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NASA's Parker Solar Probe provides a new view of Venus.

NASA’s Parker Solar Probe captured stunning views of Venus during its close flyby of the planet in July 2020, according to a press release on 24 February 2021. Although the Parker Solar Probe’s focus is the Sun, Venus plays a critical role in the mission: The spacecraft whips by Venus a total of seven times over the course of its seven-year mission, using the planet’s gravity to bend the spacecraft’s orbit. These Venus gravity assists allow Parker Solar Probe to fly closer and closer to the Sun on its mission to study the dynamics of the solar wind close to its source.

But, along with the orbital dynamics, these passes can also yield some unique and even unexpected views of the inner solar system. During the mission’s third Venus gravity assist on 11 July 2020, the onboard Wide-field Imager for Parker Solar Probe, or WISPR, captured a striking image of the planet’s nightside from 12 381 km away. 

When flying past Venus in July 2020, Parker Solar Probe’s WISPR instrument, short for Wide-field Imager for Parker Solar Probe, detected a bright rim around the edge of the planet that may be nightglow, light emitted by oxygen atoms high in the atmosphere that recombine into molecules in the nightside. The prominent dark feature in the center of the image is Aphrodite Terra, the largest highland region on the Venusian surface. Bright streaks in WISPR, such as the ones seen here, are typically caused by a combination of charged particles, called cosmic rays, sunlight reflected by grains of space dust, and particles of material expelled from the spacecraft’s structures after impact with those dust grains. The number of streaks varies along the orbit or when the spacecraft is traveling at different speeds, and scientists are still in discussion about the specific origins of the streaks here. The dark spot appearing on the lower portion of Venus is an artifact from the WISPR instrument. Guillermo Stenborg/Brendan Gallagher/Johns Hopkins University Applied Physics Laboratory/Naval Research Laboratory/NASA.

WISPR is designed to take images of the solar corona and inner heliosphere in visible light, as well as images of the solar wind and its structures as they approach and fly by the spacecraft. At Venus, the camera detected a bright rim around the edge of the planet that may be nightglow, light emitted by oxygen atoms high in the atmosphere that recombine into molecules in the nightside. The prominent dark feature in the center of the image is Aphrodite Terra, the largest highland region on the Venusian surface. The feature appears dark because of its lower temperature, about 30° C cooler than its surroundings.

That aspect of the image took the team by surprise, said Angelos Vourlidas, the WISPR project scientist from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, who coordinated a WISPR imaging campaign with Japan’s Venus-orbiting Akatsuki mission. 'WISPR is tailored and tested for visible light observations. We expected to see clouds, but the camera peered right through to the surface.'

'WISPR effectively captured the thermal emission of the Venusian surface,' said Brian Wood, an astrophysicist and WISPR team member from the U.S. Naval Research Laboratory in Washington, D.C. 'It’s very similar to images acquired by the Akatsuki spacecraft at near-infrared wavelengths.'

This surprising observation sent the WISPR team back to the lab to measure the instrument’s sensitivity to infrared light. If WISPR can indeed pick up near-infrared wavelengths of light, the unforeseen capability would provide new opportunities to study dust around the Sun and in the inner solar system. If it can’t pick up extra infrared wavelengths, then these images, showing signatures of features on Venus’ surface, may have revealed a previously unknown 'window' through the Venusian atmosphere.

NASA’s Parker Solar Probe had an up-close view of Venus when it flew by the planet in July 2020. Some of the features seen by scientists are labeled in this annotated image. The dark spot appearing on the lower portion of Venus is an artifact from the WISPR instrument. Guillermo Stenborg/Brendan Gallagher/Johns Hopkins University Applied Physics Laboratory/Naval Research Laboratory/NASA.

'Either way,' Vourlidas said, 'some exciting science opportunities await us.'

For more insight into the July 2020 images, the WISPR team planned a set of similar observations of the Venusian nightside during Parker Solar Probe’s latest Venus flyby on 20 February 2021. Mission team scientists expect to receive and process that data for analysis by the end of April.

'We are really looking forward to these new images,' said Javier Peralta, a planetary scientist from the Akatsuki team, who first suggested a Parker Solar Probe campaign with Akatsuki, which has been in orbiting Venus since 2015. 'If WISPR can sense the thermal emission from the surface of Venus and nightglow, most likely from oxygen, at the limb of the planet, it can make valuable contributions to studies of the Venusian surface.'

Parker Solar Probe is part of NASA’s Living with a Star program to explore aspects of the Sun-Earth system that directly affect life and society. The Living with a Star program is managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington. Johns Hopkins Applied Physics Laboratory designed, built and operates the spacecraft.

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European Space Agency announced plans to explore caves on the Moon.

In 2019, in a first step towards uncovering the Moon's subterranean secrets, the European Space Agency asked members of the public for to detect, map and explore lunar caves. Five ideas were selected to be studied in more detail, each addressing different phases of a potential mission. Through these five Sysnova studies, three mission scenarios were developed, one to perform a preliminary scout of entry pits and underground caves from the Moon's surface, one to lower a probe into a pit and access the first part of a cave, and one to explore an underground lava tube using autonomous rovers, as detailed in a press release issued on 21 February 2021. 'Although the studies were very different in topic and approach, they all provided great insight into potential technologies for exploring and investigating the geology of the Moon's subsurface,' says Loredana Bessone, Technical Officer for the studies and Project Manager for the European Space Agency's CAVES and PANGAEA program, speaking soon after the results of the studies were presented. 'It's been a fascinating journey, and a great opportunity for he European Space Agency to start looking into missions to explore lunar caves.'

 

Animation showing the entrance to a Lunar cave, the Marius Hills Pit. European Space Agency.

As a combination that would give a maximum scientific return, teams behind two of the studies, one from the University of Würzburg and one from the University of Oviedo, were selected to take part in an European Space Agency Concurrent Design Facility study. Both focusing on the second mission scenario, the technologies that these teams have developed would allow a safe exploration and documentation of a lunar pit as well as a first peek inside the tunnels that a pit may lead to.

Kicking off this week, the Concurrent Design Facility study is integrating the results of the studies carried out by these two teams with plans for European Space Agency's European Large Logistics Lander and Moonlight initiatives. Whilst the European Large Logistics Lander is a lander designed to enable a series of European Space Agency missions to the Moon, Moonlight aims to provide navigation and telecommunications capabilities for lunar exploration.

 

Three images of the Marius Hills pit imaged by NASA’s Lunar Reconnaissance Orbiter. This pit is about 34 metres deep and 65 by 90 metres wide. Marius Hills and other pits may be 'skylights' into extensive lava tubes. European Space Agency.

The University of Würzburg has been exploring the concept of lowering a probe using a tether to explore and characterise the entrance, walls and initial part of lunar lava tubes. These huge underground caverns are thought to have formed through lava flows billions of years ago. Named Daedalus, the compact, spherical probe would be equipped with 3D lidar, stereo camera vision and an ability to move independently. By creating a 3D model of the inside of a lava tube, the probe could identify geological resources and seek out locations with stable radiation levels and temperature; this information could take us closer to building a human settlement on the Moon.

 

A prototype developed by the University of Würzburg of the Daedalus probe that would be lowered into a lunar cave using a tether. European Space Agency.

The University of Oviedo, meanwhile, has investigated deploying a swarm of small robots inside a cave. Working together with the University of Vigo and Alén Space, the focus of their research has been on overcoming the lack of sunlight, and therefore solar power, inside a cave, as well as how to transmit data from the robots to a rover on the Moon's surface.

The team's solution is to use a crane to lower the robots into a lava tube. Equipped with a solar panel, the rover would supply energy to the robots through the crane using a 'charging head' attached to the bottom of the crane. Being in sight of the robots, the charging head would supply energy wirelessly, as well as transmitting and receiving data.

 

An overview of the University of Oviedo’s idea, where a charging head (CH) attached to the end of a crane can communicate with the underground rovers, cave elements (CEs), using WiFi. European Space Agency.

Continuing the research, the Concurrent Design Facility study will design a lunar caves mission lasting one lunar day (14 Earth days), starting from the deployment of the European Large Logistics Lander. Focusing on the second mission scenario, the Concurrent Design Facility study will also specify the individual subsystems of such a mission and ensure that they would all be able to work together.

'The Concurrent Design Facility study will investigate details such as the energy requirements of the mission, the path that could be taken from the landing site to the pit rim, and the power and data budgets for descending into and mapping the pit,' explains Francesco Sauro, cave scientist and planetary lava tube expert, as well as technical course director of the European Space Agency's CAVES and PANGAEA. 'It will also look at the interfaces between the rover and the robotic crane, as well as the crane and the Daedalus probe.'

'Overall, the Sysnova and Concurrent Design Facility studies are helping ESA to identify interesting technologies and develop roadmaps for the future. They are supporting the Agency to assess the feasibility of novel concepts for future missions.' 

 

Artist’s impression of the European Large Logistics Lander unloading cargo. This cargo could include a mission to explore lunar caves. European Space Agency. 

Whilst the Moon's surface has been well documented by orbital spacecraft, it hides an underground world that remains a mystery. The shelter that lunar caves provide, as well as the access to water and other resources, could be vital for our future human or robotic exploration of the Moon. This makes these Sysnova studies, and the ensuing Concurrent Design Facility study, a major step forward in achieving a lunar mission.

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