2024-02-25 05:00:13
On February 22, 2019, a space probe, that is to say without crew, was placed in orbit around the Moon with the objective of landing on the moon. It was a first because a private spacecraft had never landed on the lunar surface. In addition, the probe carried tardigrades in dehydrated and inactive, but viable form.
Everything was going as planned when suddenly on April 11, the probe experienced a problem with the propulsion as it began its descent. The speed was too great to be slowed down enough so that it crashed at over 3,000 km/h into our satellite (Satellite may refer to 🙂.
The shock was terrible and the probe was scattered over a hundred meters. We know this because the impact was photographed by NASA’s LRO (Lunar Reconnaissance Orbiter) satellite.
What happened to the tardigrades? Did they survive and if so can they colonize the Moon? Is the Moon contaminated?
Animals to the test of (almost) everything
Tardigrades are microscopic animals. They are less than a millimeter long. Most have two eyes, but all have neurons, a mouth orifice at the end of a retractable proboscis, an intestine containing a microbiota (The microbiota is a new name for microflora.) and four pairs of non-articulated legs ending in claws. These animals share a common ancestor (In phylogeny, a common ancestor of several species is the most…) with arthropods such as insects or arachnids.
The majority are found in aquatic environments, but they occupy all environments, even urban ones. Emmanuelle Delagouttecharge of research (Scientific research refers primarily to all actions undertaken with a view to…) at the CNRS, harvests them from mosses and lichens in the Jardin des Plantes at the Museum in Paris. Tardigrades need to be surrounded by a film of water to remain active, feed on microalgae such as chlorella, grow, move and reproduce. They reproduce sexually or asexually via parthenogenesis, that is to say from an unfertilized egg, or thehermaphrodisme (Hermaphroditism refers to a biological phenomenon in which the individual is…) when a individual (Wiktionary is a free open source dictionary project similar to Wikipedia (both…), which has both male and female gametes, self-fertilizes. After hatching from the egg, the life of a tardigrade in active form lasts from 3 to 30 months. In total, 1265 species have been describedincluding two fossils.
Tardigrades are famous for their resistance to conditions that do not exist on Earth or the Moon. They can in fact shut down their metabolism, in particular by losing up to 95% of their body water. Some species synthesize a sugar, tréhalose (Le tréhalose (α-D-glucopyranosyl-α-D-glucopyranoside ou…)which acts as antifreeze, others are proteins which are thought to incorporate cellular constituents into an amorphous “glassy” network, thus providing strength and protection to each cell.
Dehydration deforms the body, which can shrink in size by half. The paws disappear, only the claws are still visible. This state called cryptobiosis persists until conditions become favorable once more.
However, depending on the species, individuals need more or less time to dehydrate and not all specimens of the same species manage to return to active life.
Dehydrated adults survive for a few minutes at temperatures of -272°C or 150°C, and in the long term at high doses of gamma rays of 1,000 or 4,400 Gray (Gy) depending on the species. For comparison, a dose of 10 Gy is fatal for a human and 40 to 50,000 Gy sterilizes all types of equipment. However, whatever the dose, irradiation kills the eggs. Furthermore, the protection conferred by cryptobiosis is not always clear, as in the species Milnesium tardigradus where irradiation curiously affects both active and dehydrated animals in the same way.
Return to the Moon
What happened to the tardigrades following the crash? Are some still viable, buried under regolith, lunar dust whose depth varies from a few meters to a few tens of meters?
First of all, they must have survived the impact. Laboratory tests showed that frozen specimens of the species Hypsibius dujardini were intact following an impact at 2600 km/h under vacuum on sand but were mutilated beyond 3000 km/h.
They must then resist the absence of water and withstand a cold of -170 to -190°C during the lunar night and a heat of 100 to 120°C during the day. A lunar day or night lasts a long time, a little less than 15 Earth days. Even the probe was not designed to withstand such amplitudes and had to cease all activity following only a few Earth days.
Finally, the surface of the Moon is not protected from solar particles and cosmic rays, particularly gamma rays. But there the tardigrades would be able to resist. Indeed, Robert Wimmer-Schweingruber, Professor at the University of Kiel in Germany, and his team have shown that Doses of gamma rays hitting the lunar surface were permanent but small compared to the doses mentioned previously. According to him, 10 years of exposure to gamma rays would correspond to a total dose of around 1 Gy.
Regardless, without water, oxygen or microalgae, the tardigrades will never be able to reactivate. Thus the colonization of the Moon by these animals is impossible. But specimens are on lunar soil and their presence raises ethical questions as pointed out Matthew Silk Ecologist at the University of Edinburgh. Among these questions, there is one on the plan scientist (A scientist is a person who devotes himself to the study of a science or sciences and who…). At the time when theexploration (Exploration is searching with the intention of discovering something unknown.) space is starting once more in all directions, will contaminating other planets make us lose the possibility of searching for extraterrestrial life (Extraterrestrial life refers to any form of life existing elsewhere than on the planet…) ?
The author warmly thanks Emmanuelle Delagoutte and Cédric Hubas of the Paris Museum, as well as Robert Wimmer-Schweingruber of the University of Kiel, for their critical reading of the text and their advice.
1708953786
#species #colonizing #Moon
