Space Sunday: spaceship leaks, exo-Earths & an ancient solar observatory

Ammonia coolant spews from the Soyuz MS-22 vehicle docked against the Rassvet module of the International Space Station. Credit: NASA TV

A potentially serious issue occurred at the International Space Station this week when Soyuz MS-22 developed a coolant leak in the early hours of Thursday, December 14th, almost 3 months after the vehicle had docked with the station to deliver Russian cosmonauts Sergey Prokopyev and Dmitry Petelin, together with American astronaut Francisco Rubio to commence a 6-month tour of duty.

Named for Konstantin Tsiolkovsky, the father of Russian cosmonautics, the vehicle experienced an uncontrolled leak of ammonia coolant which started at 00:45 UTC and ran for several hours, generating stream of material jetting outwards from the vehicle and causing the station crew to have to stabilise the structure.

At the time the leak was detected, cosmonauts Petelina and Prokopyev were preparing to embark on a spacewalk to carry out maintenance work on the Russian segment of the ISS, where the Soyuz is docked. The EVA was called off due to concerns the cosmonaut’s spacesuits could be contaminated with the hazardous coolant fluid.

A second Russian EVA set for December 21st was also later cancelled over concerns about the leak; however, NASA initially indicated a spacewalk due to talk place on the US / International side of the station would go ahead, later deciding to postpone it in favour of assisting Roscosmos in trying to assess the amount of damage caused to the Soyuz – and possibly to the ISS.

As the leak curtailed, cosmonaut Anna Kikina – the first Russian to fly to the ISS aboard an American commercial crew vehicle as a part of a seat exchange programme between NASA and Russian space agency Roscosmos – used a European-built robotic arm attached to the Russian Nauka science module delivered to the ISS in 2021 to inspect the Soyuz craft. Further inspections by both the Russians and Americas using their respective robot arms are also being scheduled.

Operated by Anna Kikina, the European- supplied robot arm attached to the Nauka module is extended to image the exterior of Soyuz MS-22 in an attempt to assess the damage caused by the coolant leak. Credit: NASA TV

The exact nature of the leak is unknown. However, the former head of spaceflight safety at the European Space Agency Tommaso Sgobba, believed the leak occurred with the vehicle’s active coolant system, most likely crippling it “beyond repair”. This appeared to be borne out both by the images captured by Kikina using the Nauka module’s robot arm – which shoe extensive damage to the outer skin of the instrument and assembly compartment of the vehicle. Since the leak, Roscosmos has reported the interior temperatures of the vehicle’s pressure modules had risen to 30C which, despite being referred to as being within “acceptable limits”

On Friday, December 16th, 2022, the Russian space agency began remote testing of a number of the vehicle’s systems – including its thrusters – in an attempt to ascertain its space-worthiness.

If the vehicle is unfit to fly, it means Prokopyev, Petelin and Rubio will be unable to use it to make their scheduled return to Earth in March 2023 – although reports that this leaves the three “stranded” in space are somewhat exaggerated. There are a number of ways in which the three can be returned to Earth either individually or collectively:

  • Soyuz is fully capable of automated flight and docking with the ISS (it can use the same system as the Progress re-supply vehicles – themselves essentially uncrewed Soyuz – to reach the ISS and provide the three with a ride home.
  • Failing this and allowing for the necessary crew alterations, both Soyuz and Crew Dragon can fly to the ISS with a vacant seat, which can then be used by one of the MS-22 crew.
  • The Boeing CST-100 Starliner is due to make a crewed flight to the ISS in April / May 2023, a month or two after MS-22 is scheduled to return. It could, with some adjustment to the mission, be used to return one or two of the MS-22 crew as well as the main crew at the end of its week-long stay at the ISS.

Of these three options, the first would appear to be the most likely. For now however, assessments of MS-22’s overall condition are on-going and (for now) leave the door open on a fourth option: if the vehicle is deemed safe to make an immediate return to Earth, the three crew members curtail their mission and come home three months early.

The Artemis 1 mission to cislunar space is a potential watershed moment in space exploration., potentially the first genuine step in a human return to the Moon, with the potential to reach even further into the solar system. It’s a mission I covered in these pages over a number of articles, up to an including the previous piece. However, for those who would like to relive it in a compressed manner NASA has released a video of the mission’s highlight from launch to splash-down.

Running to 24 minutes – just shy of a total reflecting  the duration of the mission in days – the video is a fascinating compression of the mission, presenting many iconic images of the vehicle, the Moon and Earth.

Earth-Sized Exoplanets Update

GJ 1002 is a red dwarf stars some 16 light-years from our solar system – and now the seventh such star located in relative proximity to our Sun which is know to have Earth-sized planets orbiting it, They were discovered by a team from the Spanish Instituto de Astrofísica de Canarias (IAC) in the Canary Islands, and each is roughly comparable in mass and size to Earth, and both lie within the star’s so-called habitable zone.

With just one-eighth the mass of the Sun, GJ 1002 is a small, cool star, meaning its habitable zone – the distance at which a planet might harbour liquid water on its surface and support conditions suitable for life to gain a foothold – lies much closer to the star, – so the two planets, known as GJ 1002b and GJ 1002c, orbit their parent much faster than any planet around our own Sun: completing one orbit every 10 and 21 terrestrial days respectively.

An artist’s impression of the two Earth-mass planets orbiting the star GJ 1002. Credit: Alejandro Suárez Mascareño

The two planets were discovered using the radial velocity method  (aka Doppler spectroscopy), a technique which uses the spectrographic analysis of a star to detect a “wobble” indicative of planets affecting the star’s axial rotation / position. In this case, the team used two spectrographs: the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), an instrument on the European Southern Observatory’s VLT array high in the Atacama Desert, northern Chile, and the Calar Alto high-Resolution search for M-class dwarfs with Exo-Earths with Near-infrared and optical Échelle Spectrographs (CARMENES), located in Spain.

Both instruments were used to carry out independent observations of the star between 2017 and 2019 (CARMENES) and 2019 and 2021 (ESPRESSO) allowing for comparative studies to confirm the presence of the planets. Using overlapping capabilities, the spectrographs revealed that the atmospheres of both planets could be characterised through the amount of light they reflect and / or their own thermal emissions.

Currently, it is not apparent if either planet is capable of supporting liquid water / life – the further characterisation of their atmospheres will help with such an assessment. In particular, one issue with red dwarf stars is that they can be exceptionally violent in nature, prone to outbursts which could irradiate nearby planetary environment – although GJ 1002 is older and calmer than other M-class stars. A further factor in either planet’s ability to maintain liquid water or harbour life is that they are liable to be tidally locked to their parent – always keeping one side facing towards the star and one side away. This could result in extremes of temperature between the two sides of each planet – and potentially violent weather along the terminator.

However, it is not impossible for such planets to host liquid water, as shown in a study released by astronomers from the Université de Montréal. Their work reveals that two of the planets orbiting Kepler138, an M-class red dwarf star some 219 light-years from our solar system, are much planets.

Cross-section of the Earth (left) and the exoplanet Kepler-138 d (right). Like the Earth, this exoplanet has an interior composed of metals and rocks (brown portion), but Kepler-138 d also has a thick layer of high-pressure water in various forms: supercritical and potentially liquid water deep inside the planet and an extended water vapour envelope (shades of blue) above it. These water layers make up more than 50% of its volume, or a depth of about 2000 km. The Earth, in comparison, has a negligible fraction of liquid water with an average ocean depth of less than 4km. Credit: Benoit Gougeon, Université de Montréal

Kepler 138 is known to host at least three planetary bodies, one of which – Kepler-138b – has the lowest mass of any exoplanet discovered to date: equivalent to that of Mars. But it is Kepler-138c and Kepler-138d, each of which is about 1.5 times the size of Earth which have captured the attention of the team from UdeM.

Despite their size, both Kepler-138c and Kepler-138d have been shown to have much lower densities that Earth; were they solidly rocky bodies, their respective densities should be much greater than Earth’s. Using both the Hubble Space Telescope and the Spitzer orbiting observatory, the UdeM team suggest that a significant fraction of their volume – up to half of it – is likely made of material that is lighter than rock but heavier than hydrogen or helium – and the most likely candidate is water.

The closest comparison to the two planets, say researchers, would be some of the icy moons in the outer solar system that are also largely composed of water surrounding a rocky core. Imagine larger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star. Instead of an icy surface, Kepler-138 c and d would harbour large water vapour envelopes.

– Caroline Piaulet of the Trottier Institute for Research on Exoplanets (iREx), UdeM

Such is the proximity of the two planets to their parent, it is unlikely either would have surface oceans in a form we would recognise; simply put, the surface of any ocean on the sunward side either planet would be above the boiling point of water. This means that instead, each world is likely to be wreathed in an atmosphere of water vapour and steam which condenses the deeper into it one gets until it simply becomes a supercritical fluid. Again, these are hardly ideal circumstances under which lift as we understand it, but it opens the door to the existence of so-called water worlds within our galaxy.

How the Aztecs Used the Sun to Manage Their Agriculture

The Aztecs were, in their time, the most dominant civilisation within Mesoamerica (Pre-Columbian Mexico). They remain renown for being a somewhat bloody, but nevertheless highly capable – in terms of engineering, agronomy and astronomy.

At the height of their power, the Aztec Empire supported a population of up to 3 million in the Valley of Mexico, with cities such as Tenochtitlan, Texcoco, and Tlacopan supporting populations exceeding 100,000. Supporting such a large population in a region noted for its arid springs and monsoon-like autumn / winter periods relied upon an advanced understanding of when seasonal variations in weather, allowing the Aztecs to know when to plant and harvest their crops to achieve the best yields, and to be able to adjust for known seasonal variations. That the Aztecs utilised incredibly details agricultural calendars to achieve this has long been know; however exactly how the accuracy of these calendars was achieved has remained something of a mystery.

Now a research team led by the University of California Riverside (UCR) suggests the Aztecs studied the Sun in enormous detail, using both an observatory in the Sierra Nevada mountains and the entire length of the Valley of Mexico.

They must have stood at a single spot on Mount Tlaloc at the northern most end of the Sierra Nevada range, looking eastwards from one day to another, to tell the time of year by watching the rising Sun. Their working instrument was the Basin itself. When the sun rose at a landmark point behind the Sierras, they knew it was time to start planting.

Exequiel Ezcurra, professor of ecology, Department of Botany and Plant Sciences, UCR

A stone causeway atop Mount Tlaloc, believed to be a part of an Aztec observatory used for charting the Sun’s movement for agricultural purposes. Credit: Ben Messiner/UCR

In particular, the Aztecs were adept at using solar declination – tracking the angular distance of the sun’s rays north (or south) of the equator as it rises and sets at different points on the horizon throughout the year as the Earth moves around the Sun. These observations allowed the Aztecs to construct calendars capable of predicting when season changes – notably summer to winter – would occur, and when spring would offer the optimal times to plant crops.

The use of the observatory and the Valley should not be confused the the idea of the “Sun Stone” Aztec calendar. While the latter contains representations of the two calendars they maintained (the 365-day solar and the 260-day ceremonial calendar), the Stone is believed to have served a ceremonial purpose only.

Whilst providing insight into how the Aztecs managed the crops, the observatory could serve another function today, but providing insight into climate change. In the 80 years since the 1940s, the region has been subject to multiple studies of the Aztec sites throughout the Valley of Mexico, allowing a considerable amount of photographic evidence to be gathered, These records reveal how, over the decades, increasing temperatures throughout the valley and its mountains have resulted in a rising tree-line. Where once the majority of the mountain peaks lay above the tree-line, today many are wreathed in a woodlands.