Dados recolhidos pela sonda espacial Cassini, já desativada, revelaram a presença de fósforo em forma de fosfatos, um componente-chave da vida tal como se conhece, no oceano gelado de Enceladus, uma das luas de Saturno.
A sonda explorou Saturno, o seu sistema de anéis e as suas luas durante 13 anos, entre 2004 e 2017, mas os seus dados continuam a ser estudados pelos cientistas.
Segundo os autores da investigação, publicada esta quarta-feira na revista científica Nature, foi encontrado "abundante fósforo" em grãos de gelo expelidos para o espaço desde as fendas da superfície gelada de Enceladus.
A lua possui um oceano subterrâneo e a água desse oceano irrompe através de fendas na crosta gelada da superfície como geiseres, no polo sul, criando uma pequena nuvem que alimenta um dos anéis de Saturno com partículas de gelo. A análise de uma classe de grãos de gelo ricos em sal revelou a presença de fosfatos de sódio - moléculas de sódio, oxigénio, hidrogénio e fósforo quimicamente ligadas.
As concentrações de fosfato provenientes de Enceladus são pelo menos 100 vezes superiores às dos oceanos da Terra, de acordo com o estudo.
O fósforo na forma de fosfatos é fundamental para a vida na Terra, nomeadamente para a criação de material genético, moléculas portadoras de energia, membranas celulares, ossos e dentes de pessoas e animais e microbioma do plâncton.
É a primeira vez que este elemento químico essencial é descoberto num oceano sem ser os mares da Terra. Estudos anteriores supunham a existência de fósforo em Encélado, apenas agora confirmada com os dados da sonda Cassini.
Enceladus e as possibilidades de existência de vida tinham estado em destaque há pouco tempo, pela descoberta de uma pluma gigantesca de vapor de água que se estende por quase 10 mil quilómetros, captada pelo telescópio espacial James Webb.
Clique nas imagens para ver com mais detalhe
Enceladus é um mundo oceânico com cerca de 4% do tamanho da Terra - pouco mais de 500 quilómetros de diâmetro - e um dos alvos científicos mais expectantes na busca por vida extraterrestre no Sistema Solar.
Com a Cassini reformada, caberá ao “jovem” James Webb ser a principal ferramenta de observação da lua de Saturno. As descobertas do telescópio espacial irão ajudar a preparar futuras missões, com vista a explorar a profundidade do oceano subterrâneo e a espessura da crosta de gelo, entre outros pormenores.
Clique nas imagens para mais detalhes sobre as “espreitadelas cósmicas” de James Webb
![This image of interacting galaxies Arp 142, captured by the James Webb Space Telescope’s NIRCam (Near-InfraRed Camera) and MIRI (Mid-InfraRed Instrument), shows compass arrows, a scale bar, and a colour key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). The scale bar is labelled in light-years, which is the distance that light travels in one Earth-year. (It takes three years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 9.46 trillion kilometres. The scale bar is also labelled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute. (The full Moon has an angular diameter of about 30 arcminutes.) The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope. This image shows invisible near- and mid-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam and MIRI filters were used when collecting the light. The name of each filter is the visible light colour used to represent the infrared light that passes through that filter. [Image description: Two interacting galaxies known as Arp 142. At left is NGC 2937, nicknamed the Egg for its appearance. At right is NGC 2936, nicknamed the Penguin for its appearance. The latter’s beak-like region points toward and above the Egg.]](https://mb.web.sapo.io/a4abd86df8fd1af368a46d5331c138ff3b2c13d7.jpg)
![This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows a portion of the GOODS-North field of galaxies. At the lower right, a pullout highlights the galaxy GN-z11, which is seen at a time just 430 million years after the Big Bang. The image reveals an extended component, tracing the GN-z11 host galaxy, and a central, compact source whose colours are consistent with those of an accretion disc surrounding a black hole. [Image description: A rectangular image with thousands of galaxies of various shapes and colours on the black background of space. Some are noticeably spirals, either face-on or edge-on, while others are blobby ellipticals. Many are too small to discern any structure. One prominent foreground star at top centre features Webb’s signature eight-point diffraction spikes. At lower right, a small region is highlighted with a white box. Vertical lines extend upward like a cone to the bottom corners of a larger box at upper right, showing a zoomed-in version of the highlighted area. The pullout features a galaxy labelled GN-z11, seen as a fuzzy yellow dot. Above it is another galaxy, seen as a fuzzy red oval.]](http://mb.web.sapo.io/f6f30cda88cbe87e155871ba5170c9132f94fd15.jpg)
![This two-part graphic shows evidence of a gaseous clump of helium in the halo surrounding the galaxy GN-z11. In the top portion, at the far right, a small box identifies GN-z11 in a field of galaxies. The middle box shows a zoomed-in image of the galaxy. The box at the far left displays a map of the helium gas in the halo of GN-z11, including a clump that does not appear in the infrared colours shown in the middle panel. In the lower half of the graphic, a spectrum shows the distinct ‘fingerprint’ of helium in the halo. The full spectrum shows no evidence of other elements and so suggests that the helium clump must be fairly pristine, made almost entirely of hydrogen and helium gas left over from the Big Bang, without much contamination from heavier elements produced by stars. Theory and simulations in the vicinity of particularly massive galaxies from these epochs predict that there should be pockets of pristine gas surviving in the halo, and these may collapse and form Population III star clusters. [Image description: A graphic labelled Galaxy GN-z11, Pristine Gas Clump Near GN-z11. The graphic is divided into two sections. The top half of the graphic features a rectangular image of a field of galaxies with two pullouts, the second of them labelled Helium Two Detected. The bottom half shows a single line graph.]](http://mb.web.sapo.io/e88335c0ecb525e2977cdb7fda8db35d60433f94.jpg)
![This image of the GOODS-North field, captured by Webb’s Near-Infrared Camera (NIRCam), shows compass arrows, a scale bar, and a colour key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). The scale bar is labelled in angular distance on the sky, where one arcsecond is one 3600th of a degree. The scale bar is 60 arcseconds long. This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter. [Image description: A rectangular image shows thousands of galaxies of various shapes and colours on the black background of space. The pullout features a galaxy labelled GN-z11, seen as a fuzzy yellow dot. Above it is another galaxy, seen as a fuzzy red oval. To the left of the small box, a scale bar is labelled 60 arcseconds. It extends about one tenth of the way across the image. Below the image, a list of NIRCam filters show what colours were used to make the image. Filters shown in blue are F090W, F115W, and F150W. Filters shown in green are F200W, F277W, and F335M. Filters shown in red are F356W, F410M, and F444W.]](http://mb.web.sapo.io/e5b881b601f585337061240e616183a872385437.jpg)
![This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows a portion of the GOODS-North field of galaxies. [Image description: A rectangular image with thousands of galaxies of various shapes and colours on the black background of space. Some are noticeably spirals, either face-on or edge-on, while others are blobby ellipticals. Many are too small to discern any structure. One prominent foreground star at top centre features Webb’s signature eight-point diffraction spikes.]](http://mb.web.sapo.io/2041446b9a53fd51681679e5383d06e674e14b2e.jpg)
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