On Thursday, February 10th, 2024, NASA launched a critical Earth observation satellite intended to study the world’s oceans and atmosphere in the face of increasing climate change.
PACE – the Plankton, Aerosol, Cloud, ocean Ecosystem remote sensing platform – is designed to operate in a geocentric, near-polar Sun-synchronous orbit, allowing it to observe all of Earth’s atmosphere and oceans over time. In doing so, it will study how the ocean and atmosphere exchange carbon dioxide and how microscopic particles (aerosols) in our atmosphere might fuel phytoplankton growth in the ocean. The data it accumulates will be used to identify the extent and duration of harmful algae blooms and extend NASA’s long-term observations of our changing climate.
Referred to as autotrophic (self-feeding), phytoplankton are present in both oceanic and freshwater ecosystems and play a key role in sustaining them – and in managing the planet’s carbon dioxide absorption and oxygen production. With the former, phytoplankton absorb carbon dioxide from the atmosphere and convert it into their cellular material, serving as the base of the global aquatic food web, a critical resource for countless species – including humans. In terms of the latter, phytoplankton are responsible for around half the planet’s natural oxygen production despite being around just 1% of the global plant biomass.
Occupying the photic zone of oceans, where photosynthesis is possible, phytoplankton are crucially dependent on large quantities of nutrients, including nitrate, phosphate or silicic acid, iron, and also large amount of vitamin B. The availability of these nutrients is governed by a range of factors: the so-called ocean carbon biological pump; nutrients delivered into the photic zone via freshwater sources emptying into the oceans, natural organic decay, etc.
Both anthropogenic global warming and pollution are particularly harmful to phytoplankton; the former can lead to both changes in the vertical stratification of the water column and the supply of nutrients vital to phytoplankton. Similarly, increased acidity within ocean waters and currents can also adversely affect phytoplankton, up to an including causing biochemical and physical changes. In this, the colour changes exhibited by phytoplankton are considered important indicators of estuarine and coastal ecological condition and health.
Thus, the study of the global distribution and health of phytoplankton communities could profoundly advance our knowledge of the ocean’s role in the climate cycle, whilst at the same time providing real-time data on the negative effects of coastal and deep-water pollution and the impact of climate change and increasing temperatures on the world’s aquatic ecosystem.
In this, PACE will operate in unison with the French-American Surface Water and Ocean Topography (SWOT) mission. Launched in 2022, SWOT is designed to make the first global survey of the Earth’s surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time to allow a more complete picture of the impact of anthropogenic global warming and pollution on the planet’s aquatic biodiversity and life-giving water cycle.
“Death Star” Moon’s Underground Ocean
We’re becoming increasingly familiar with the solar system being potentially full of so-called “water worlds” – bodies that may be home to vast subsurface oceans. Jupiter’s Europa and Saturn’s Enceladus are perhaps the most well-known, with both showing visible signs of water vapour escaping in geyser plumes through cracks in their surfaces. However, there are other bodies scattered around the solar system where water could be present beneath their surfaces, if not in liquid form, then at least in either a semi-liquid icy slush or solid ice.
Now a team of French-led scientists believe they have another candidate for holding a sub-surface ocean: Saturn’s moon Mimas.
This tiny moon – officially designated Saturn I – is the smallest astronomical body yet found in our solar system known to be roughly rounded in shape due to its own gravity. However, Mimas – with a mean diameter of 396.4 km – is perhaps most famous for resembling the fictional Death Stars of the Star Wars franchise. This is because one face of the moon is dominated by a huge, shallow impact crater 139 kilometres across, which has an almost sinister resemblance to the depression housing the primary weapon found on the fictional doomsday space vehicle.
Discovered in 1789 by William Herschel – after whom the distinctive crater is named – Mimas is responsible for one of the largest gaps in Saturn’s complex ring system, the Cassini Division, and had long be thought to be primarily made up of water ice rather than rock, simply because of its relatively low density (1.15 g/cm³).
However, the research team, using data gathered by the NASA / ESA Cassini mission which studied Saturn and its complex system of moons and rings between July 1st, 2004 and September 15th, 2017 (Space Sunday: Cassini – a journey’s end), believe that Mimas most likely has a watery ocean which exists at around the freezing point of water where it is closest to the moon’s surface, whilst potentially being several degrees warmer at the sea floor.
Building models to account for the moon’s mass and motion, and which also incorporate data on potential core warming and tidal flexing due to the influence of Saturn and other bodies orbiting the planet, the research team concluded that it is likely the ocean on Mimas accounts for around 50% of its total volume, and reach up to around 30 or 20 km below the moon’s crust. This would put the total amount of water within the moon at around 1.2%-1.4% that of all the Earth’s oceans; a not inconsiderable volume, given Mimas’ tiny size.
What has excited planetary astronomers the most, though, is the suggestion that this ocean might only be around 15 million years old – too young to have influenced the moon’s surface, but old enough that – assuming the conditions within it were right – it might actually be home to basic life still in the earliest stages of development; not that actually studying that life would be in any way easy (if at all possible). Even so, Mimas has possibly revealed that even the tiniest bodies in our solar system, if given the right circumstances, could be home to bodies of liquid water and perhaps to the basics of life.
Second CLPS Lunar Mission Set for Valentine’s Day Launch
The second private mission to fly to the Moon under NASA’s Commercial Lunar Payload Services (CLPS) programme is set to launch on February 14th, 2024.
The 675 kg IM-1 lander, also known as a Nova-C lander and christened Odysseus by its makers, has been built by Intuitive Machines, a Texas-based start-up. It had originally been scheduled to be the first lunar lander to be launched under the CLPS programme, in October 2021. However, a series of slippages – one of which one of the losing parties (Deep Space Systems) for the CLPS contract unsuccessfully challenging the US $77 million award – led to the mission being pushed back several times, enabling the recent Astrobotic Peregrine Mission One to claim the title of the first successful CLPS mission launch (January 8th, 2024 and the maiden flight of the ULA Vulcan Centaur rocket).
Intuitive machines, who will be using a SpaceX Falcon 9 rocket as their launch vehicle, are hoping for a better result than that of Astrobotic – as I reported at the time, whilst the launch of the latter mission was successful, the lander suffered a malfunction and never reached the Moon, instead eventually re-entering Earth’s atmosphere and burning up.
Odysseus will be carrying 12 payloads to the Moon – six provided by NASA and 6 privately-funded. Included in the latter are sculptures by artist Jeff Koons entitled Moon Phases, and are tied to his first foray into the rabbit hole of NFTs (and in the process potentially furthering his critics’ view that his work could be considered little more than cynical self-merchandising). However, its sculptures will form the first set of sculptures to reach the Moon since 1971, when Apollo 15 astronaut David Scott placed the 9-cm tall Fallen Astronaut by Belgian artist Paul Van Hoeydonck on the Moon alongside a plaque commemorating the astronauts and cosmonauts who have lost their lives in space missions up until that time.
Also aboard the lander is a system called EagleCAM, a camera system designed to gain the first ever “third-person” images of a vehicle landing on the Moon. It will attempt to achieve this by being ejected from the lander when it is 30 metres above the lunar surface. Falling ahead of the lander, it is hoped EagleCAM will arrive on the Moon in such a way that one of his lens will be pointing at the landing site, allowing it to record Odysseus’ arrival. Any images it does capture will be transmitted to the lander via a wi-fi connection for transfer to Earth.
The NASA instruments include a laser retro-reflector array (LRA), designed to provide precise measurements of the distance between the Earth and the Moon using lasers fired from Earth. Six LRAs were left on the Moon by the Apollo missions, and three more have been placed by the two Soviet Lunokhod rover missions of the 1970s, and one by the Indian Vikram lander in 2023.
The lander also carries the Lunar Node-1 (LN-1) prototype for a radio navigation system NASA hopes to utilise on the Moon for precise geolocation (or should that be selenolocation?) and navigation. The idea is that every unit on the Moon – base camps, rovers, astronauts, landers – and incoming vehicles – will have such beacons, and will be able to use the signals from multiple beacons to precisely confirm their position relative to one another. In theory, such a system would allow an automated lander make a precise landing wherever it was required, or allow two rovers to rendezvous with one another without the need for mission controller Earthside to direct them. LN-1 would therefore provide a local radio navigation system, one of several options for surface vehicle and lander navigation being investigated by NASA.
Following its launch at 05:57 UTC on February 14th, Odysseus will make a 5-day cruise to the Moon and has a provisional landing date of February 19th, 2024. It is due to land at Malapert A, an impact crater near the southern limb of the Moon and once on the surface, it is expected to operate for some 14 days – as long as the Sun is above the horizon to provide it with energy.
The total cost of the mission to NASA has been US $118 million, including some US $40 million towards launch and operation costs associated with the Falcon 9 rocket.
Welcome to Volcano Central: A Stunning View of Io
On December 30th, 2023, the NASA Juno spacecraft (of the mission of the same name), which has been orbiting Jupiter since July 2016, returning a huge amount of data and images of the solar system’s largest planet and its retinue of moons, made its closest approach to Io, the most volcanically active place in the solar system.
At that time, the orbiter passed over the north hemisphere of Io at a distance of 1,500 km. In February 2024, the spacecraft made a second pass over Io, this time over the moon’s southern hemisphere, and these two passes have allowed the production of the sharpest images of the moon ever seen to date.
At the innermost of the four large Galilean Moons of Jupiter, Io is very slightly larger than our Moon, and has the highest density of any moon in the solar system. With some 400 active volcanoes being recorded on its surface, it is not only the most volcanically active place in the solar system – it is the most geologically active, courtesy of its surface being almost constantly re-shaped by volcanic outflows.
The cause on all this volcanism is primarily because Io is constantly being tidally flexed: on the one side, it has massive Jupiter pulling away at it and its molten core. On the other, it has the three other Galilean moons, each of which exerts its own pull on Io, and all of which periodically combine their forces to counter Jupiter. In addition, Io sits well inside Jupiter’s immensely powerful magnetic field, which also imposes tidal forces on the moon’s core, further causing it to flex and generate heat and energy.
The images from the two recent passes over Io by Juno have been combined into a single true-colour mosaic, with the moon almost equally lit on two sides by direct sunlight and sunlight reflected onto it by Jupiter’s nearby bulk. The result is an image stunning in its clarity and depth of detail.
Many of Io’s volcanoes are visible, with at least one puffing out a plume of ejecta. On the sunward side of the moon (to the right) the light of the Sun is sufficient to reveal the moon’s hazy, mineral-rich atmosphere, whilst large parts of the surface appear bland and smooth due to the outflow of lava from multiple eruptions, and upon which volcanic island appear to be dotted.
A further impressive aspect of this image is that it was not created by NASA or anyone at Malin Space Science Systems (MSSS), who made and manage the mission’s JunoCAM imager. Instead, it was pieced together and processed by citizen-scientist Emma Wälimäki, using raw Juno images presented by NASA for public consumption, as a part of her involvement in the NASA citizen-science programme.
Inara Pey: Living in a Modemworld 