This artist’s concept depicts the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). NASA's Mars Atmosphere and Volatile Evolution is in orbit of the Red Planet to study its upper atmosphere, ionosphere and interactions with the sun and solar wind.
Credits: NASA’s Goddard Space Flight Center
Solar wind and radiation are responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, according to new results from NASA's MAVEN spacecraft.
"We've determined that most of the gas ever present in the Mars atmosphere has been lost to space," said Bruce Jakosky, principal investigator for the Mars Atmosphere and Volatile Evolution Mission (MAVEN), University of Colorado in Boulder. The team made this determination from the latest results, which reveal that about 65 percent of the argon that was ever in the atmosphere has been lost to space. Jakosky is lead author of a paper on this research to be published in Science on Friday, March 31.
In 2015, MAVEN team members previously announced results that showed atmospheric gas is being lost to space today and described how atmosphere is stripped away. The present analysis uses measurements of today’s atmosphere for the first estimate of how much gas was lost through time.
Liquid water, essential for life, is not stable on Mars' surface today because the atmosphere is too cold and thin to support it. However, evidence such as features resembling dry riverbeds and minerals that only form in the presence of liquid water indicates the ancient Martian climate was much different – warm enough for water to flow on the surface for extended periods.
This infographic shows how Mars lost argon and other gasses over time due to ‘sputtering.’ Click to enlarge.
“This discovery is a significant step toward unraveling the mystery of Mars' past environments,“ said Elsayed Talaat, MAVEN Program Scientist, at NASA Headquarters in Washington. “In a broader context, this information teaches us about the processes that can change a planet’s habitability over time.”
There are many ways a planet can lose some of its atmosphere. For example, chemical reactions can lock gas away in surface rocks, or an atmosphere can be eroded by radiation and a stellar wind from a planet's parent star. The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate. The solar wind is a thin stream of electrically conducting gas constantly blowing out from the surface of the sun.
The early Sun had far more intense ultraviolet radiation and solar wind, so atmospheric loss by these processes was likely much greater in Mars' history. According to the team, these processes may have been the dominant ones controlling the planet's climate and habitability. It's possible microbial life could have existed at the surface early in Mars’ history. As the planet cooled off and dried up, any life could have been driven underground or forced into rare surface oases.
Jakosky and his team got the new result by measuring the atmospheric abundance of two different isotopes of argon gas. Isotopes are atoms of the same element with different masses. Since the lighter of the two isotopes escapes to space more readily, it will leave the gas remaining behind enriched in the heavier isotope. The team used the relative abundance of the two isotopes measured in the upper atmosphere and at the surface to estimate the fraction of the atmospheric gas that has been lost to space.
As a "noble gas" argon cannot react chemically, so it cannot be sequestered in rocks; the only process that can remove noble gases into space is a physical process called "sputtering" by the solar wind. In sputtering, ions picked up by the solar wind can impact Mars at high speeds and physically knock atmospheric gas into space. The team tracked argon because it can be removed only by sputtering. Once they determined the amount of argon lost by sputtering, they could use this information to determine the sputtering loss of other atoms and molecules, including carbon dioxide (CO2).
CO2 is of interest because it is the major constituent of Mars' atmosphere and because it's an efficient greenhouse gas that can retain heat and warm the planet. "We determined that the majority of the planet's CO2 was also lost to space by sputtering," said Jakosky. "There are other processes that can remove CO2, so this gives the minimum amount of CO2 that's been lost to space."
The team made its estimate using data from the Martian upper atmosphere, which was collected by MAVEN's Neutral Gas and Ion Mass Spectrometer (NGIMS). This analysis included measurements from the Martian surface made by NASA's Sample Analysis at Mars (SAM) instrument on board the Curiosity rover.
"The combined measurements enable a better determination of how much Martian argon has been lost to space over billions of years," said Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Using measurements from both platforms points to the value of having multiple missions that make complementary measurements." Mahaffy, a co-author of the paper, is principal investigator on the SAM instrument and lead on the NGIMS instrument, both of which were developed at NASA Goddard.
The research was funded by the MAVEN mission. MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics, Boulder, and NASA Goddard manages the MAVEN project. MSL/Curiosity is managed by NASA's Jet Propulsion Laboratory, Pasadena, California.
(CAPE CANAVERAL, Fla.) — SpaceX has launched its first recycled rocket.
It's the biggest leap yet in the company's bid to drive down costs and speed up flights.
The Falcon 9 rocket blasted off from Florida's Kennedy Space Center Thursday evening on the historic reflight. It's the first time SpaceX founder Elon Musk has tried to fly a salvaged booster. The first stage landed on an ocean platform almost a year ago after a launch for NASA.
SpaceX refurbished and tested the booster, which still has its original engines. The booster will aim for another sea landing once it hoists a broadcasting satellite for the SES (S-E-S) company of Luxembourg.
Longtime customer SES is getting a discount for agreeing to use a recycled rocket, but won't say how much.
ANSA.IT - Scoperta la stelle più 'pura' mai vista finora, è composta per il99,99% daelio e idrogenoe hacirca10 miliardi di anni, circa il doppio rispetto al Sole. La piccola stella, una cosiddettanana bruna, è stata identificata da ZengHua Zhang, dell'Istituto di Astrofisica delle Canarie, e descritta sulla rivista Monthly Notices of the Royal Astronomical Society.
Le stelle non sono tutte uguali: variano moltissimo in base alla loro massa, che può andare da un minimo di un decimo quella del Sole fino a oltre 200 o 300 volte, come l'ipergigante R136a1 che si trova nella Grande Nube di Magellano.
Distante 750 anni luce dalla Terra, nella costellazione dei Pesci, la stella 'purissima' è stata scoperta grazie alle immagini scattate dal Very Large Telescope (Vlt) dell'Osservatorio Meridionale Europeo (Eso) e appartiene alla 'famiglia' delle stelle più piccole. La sua massa è di circa 90 volte quella di Giove e ciò la rende troppo 'piccola' per far innescare al suo interno le reazioni di fusione nucleare, durante le quali l'idrogeno viene trasformato in elio e avviene un intenso rilascio di energia.
Analizzando i dati, i ricercatori sono riusciti a determinare la composizione della nana bruna, chiamata SDSS J0104+1535, scoprendo che è formata per il 99,99% di idrogeno e elio, una purezza record. I dati indicano inoltre che la stella è molto antica, avrebbe ben 10 miliardi di anni fa, e indica che si sarebbe formata a partire dai gas che componevano l'universo primordiale. “Davvero non ci aspettavamo di vedere una nana bruna di tale purezza – ha commentato Zhang – e averne trovato anche solo una potrebbe suggerire che ne esistano molte altre mai osservate finora”.
ANSA.it - Galileo scoprì che Venere al telescopio mostra le fasi proprio come la Luna: durante la sua rivoluzione attorno al Sole la possiamo vedere "piena", al "quarto" e persino "nuova".
Normalmente Venere si vede soltanto quando è più lontana dal Sole e si mostra come "stella della sera" o "stella della mattino", e risulta invisibile invece quando passa più vicino al Sole, sovrastata dalla sua luce accecante. Questa fase è l'equivalente per Venere della Luna nuova, quando il nostro satellite è invisibile.
La fotografia, ripresa il 26 marzo 2017 da Paolo Colona dell'Accademia delle Stelle, ritrae Venere mentre passa dal periodo di visibilità serale a quello mattutino, immersa nel bagliore del Sole.
Questa transizione si chiama "scavalcamento di fase" e, al momento dello scatto, ripreso con un telescopio in pieno giorno, il pianeta si trovava ad appena appena 8 gradi dal Sole.
ANSA.it - Sono state riprodotte sulla Terra le collisioni cosmiche che creano l'antimateria, teatro dell'esperimento è stato il più grande acceleratore di particelle al mondo, il Large Hadron Collider (Lhc) del Cern. I primi risultati dell'esperimento ideato da ricercatori dell'Istituto Nazionale di Fisica Nucleare (Infn) sono stati presentati alla conferenza Rencontres de Moriond 2017, a La Thuile (Aosta), aiuteranno a capire meglio la natura dell'antimateria e della materia oscura.
L'esperimento chiamato Smog ha fatto scontrare un fascio di particelle cariche spinte ad altissima velocità all'interno dell'acceleratore con una 'nuvoletta' di atomi di elio. Il meccanismo ha simulato un fenomeno che avviene solitamente nello spazio e che è al centro di due importanti esperimenti scientifici, Pamela, installato a bordo di un satellite, e Ams-02, che si trova agganciato alla Stazione Spaziale Internazionale e che indaga la natura della misteriosa materia oscura.
L'idea di Smog nasce da un gruppo di fisici, sia teorici che sperimentali, attivi su progetti di fisica astroparticellare presso le sezioni Infn di Catania, Firenze e Torino, ed è stato proposto alla collaborazione Lhcb. "La misura realizzata - ha detto Oscar Adriani, direttore della Sezione Infn di Firenze - contribuirà a ridurre le incertezze presenti sulla stima degli antiprotoni secondari nei raggi cosmici, dando quindi la possibilità di una interpretazione più chiara delle difficili misure sugli antiprotoni effettuate da Pamela e Ams-02, ed è una chiara dimostrazione dell'importanza della multidisciplinarietà in ambito scientifico".
For at least a million years, an asteroid orbiting the “wrong” way around the sun has been playing a cosmic game of chicken with giant Jupiter and with about 6,000 other asteroids sharing the giant planet’s space, says a report published in the latest issue of Nature. The asteroid, nicknamed Bee-Zed, is the only one in this solar system that’s known both to have an opposite, retrograde orbit around the sun while at the same time sharing a planet’s orbital space, says researcher and co-author Paul Wiegert of Western’s Department of Physics and Astronomy.
All but 82 of the million or so known asteroids in our solar system travel around the sun in what’s called a prograde motion: that is, counter-clockwise when visualized from above. But asteroid 2015 BZ509 (“Bee-Zed” for short) circles clockwise, in a retrograde motion – moving against the flow of all other asteroids in the giant planet’s orbital entourage.
Put another way, it’s as if Jupiter is a monster truck on a track circling the sun, and the asteroids in Jupiter’s orbit are sub-compact cars all whizzing along in the same direction. Bee-Zed is the rogue —driving around the track in the wrong direction — steering between the 6,000 other cars and swerving around the monster truck. And it does so every single lap, and has done so for thousands of laps for a million years or more.
So how does it avoid colliding with Jupiter? Jupiter’s gravity actually deflects the asteroid’s path at each pass so as to allow both to continue safely on their way, Wiegert says.
Little is known about the asteroid, which was discovered in January, 2015. It has a diameter of about three kilometers and it may have originated from the same place as Halley’s comet, which also has a retrograde orbit. The team hasn’t been able to determine yet if Bee-Zed is an icy comet or a rocky asteroid.
But their analysis – based on complex calculations and on observations through the Large Binocular Camera on the Large Binocular Telescope in Mt. Graham, Arizona, during a span of 300 days — show Bee-Zed is somehow able to maintain a stable orbit even as an outlier.
The calculations conducted by the team show the orbit has been stable for at least a million years and will be stable for at least a million more. Learning more about the asteroid provides another intriguing glimpse into previously unknown and unmapped features of our solar system. “The detective work has just begun,” he said.
Co-researchers with Wiegert are Martin Connors of Athabaska University Observatories in Alberta, University of Calgary’s Department of Physics and Astronomy and the Institute for Space-Earth Environmental Research at the University of Nagoya, Japan; and Christian Veillet of the Large Binocular Telescope Observatory in Tucson, Arizona. Their work was supported in part by the Natural Sciences and Engineering Council of Canada (NSERC).
Comet 41P/Tuttle-Giacombini-Kresák zooms past the barred spiral galaxy NGC 3198 in this photo taken by astrophotographer Chris Schur on March 14. At the time, the glowing, green comet was about 16 million miles (25 million kilometers) from Earth. This "April Fool's Day Comet" will make its closest approach on April 1, passing within 13.7 million miles (22 million km) of the Earth. NGC 3198, also known as Herschel 146, may appear close by, but it lies 47 million light-years away in the constellation Ursa Major.
An unusually favorable opportunity to view a famous periodic comet in small telescopes comes during the next couple of weeks, when passes closer to Earth than at any return since its discovery in 1858.
The comet's perihelion point, which is that part of its orbit taking it closest to the sun, lies just outside Earth's orbit. This year, the perihelion passage occurs April 12, when the comet will be 97.1 million miles (156.3 million kilometers) from the sun. But because the orbit of the comet nearly parallels the orbit of Earth at this point, there will be a six-day period — from March 29 through April 3 — when Tuttle-Giacobini- Kresák will be very near to its closest point to Earth.
The comet will, in fact, be closest to Earth on April Fools' Day (April 1); just about 13.2 million miles (21.2 million km) away.
EFE.com - A agência espacial americana, Nasa, apresentou um novo relógio atômico com o qual espera melhorar e simplificar a navegação pelo espaço.
Em comunicado divulgado nesta quarta-feira, a Nasa revelou o Deep Space Atomic Clock, uma nova geração de relógios atômicos desenvolvida no Laboratório de Propulsão a Jato da agência na cidade de Pasadena, na Califórnia.
A Nasa informou que em fevereiro integrou este novo instrumento no satélite Surrey Orbital Test Bed, que será lançado no final deste ano.
"A precisão (ao medir o tempo) exerce um papel crítico na navegação especial e será especialmente importante para as futuras missões no espaço sideral", detalhou a nota oficial.
A agência explicou que a maioria dos dispositivos de exploração espacial utiliza um método de rastreamento de duplo sentido pelo qual uma antena na Terra emite um sinal e, posteriormente, após receber o retorno da nave, calcula a distância e determina se a nave deve variar ou manter o rumo.
Este novo relógio atômico permitirá que os dados sejam processados diretamente na nave, por isso não será mais necessário o sinal de retorno até a Terra.
A Via Láctea era em suas origens uma massa poeirenta, com altos índices de formação de estrelas e com densas camadas estendidas de gás, segundo as observações feitas de outras formações similares a nossa galáxia quando o Universo estava em suas primeiras fases.
Graças à alta sensibilidade do telescópio Atacama Large Millimeter Array (ALMA), situado no deserto do Atacama, no Chile, os astrônomos observaram duas galáxias similares à Via Láctea quando o Universo tinha apenas 8% de sua idade atual, segundo um estudo publicado nesta quinta-feira pela revista "Science".
Essas galáxias em espiral que são como um dia foi a Via Láctea, estão rodeadas de "super-halos" (grandes anéis) de hidrogênio que se estendem por centenas de milhares de anos luz além de seus discos poeirentos e repletos de estrelas.
Durante décadas, para observar as galáxias distantes os astrônomos buscaram a forma característica em que seus gases absorvem a luz brilhante dos quasares que se situam em um segundo plano das formações estelares.
A luz desses quasares distantes, ao passar pelas galáxias que encontra em seu caminho em direção ao planeta Terra pode registrar a "assinatura espectral", um tipo de radiação do gás de uma galáxia, mas que é muito difícil de detectar.
"Imagine um pequeno vaga-lume junto a um projetor de alta potência. É isso com que os astrônomos se deparam quando querem observar essas versões juvenis de nossa galáxia", afirmou o autor principal de estudo, Marcel Neeleman, da Universidade da Califórnia (EUA).
As tentativas de observar diretamente a luz dessas galáxias distantes foram, em sua maioria, infrutíferas. Mas, agora, um grupo de astrônomos conseguiu ver suas emissões, o que oferece a oportunidade "de saber coisas sobre os primeiros tempos da história de nossa galáxia e de outras similares a ela", acrescentou Neeleman.
No entanto, o resultado não foi o esperado. Os astrônomos acreditavam que veriam frágeis emissões acima do quasar, mas, na realidade, observaram "fortes e brilhantes emissões de carbono procedentes das galáxias e muito afastadas dos quasares situados em segundo plano", explicou o professor de Astronomia da mesma universidade, Xavier Prochaska.
Os dados procedentes do ALMA também revelam que as duas galáxias estão cerca de 12 bilhões de anos luz da Terra e formam estrelas a uma velocidade "moderadamente alta".
Além disso, os especialistas resolveram uma questão que já os intrigava há uma década sobre a formação das galáxias, pois agora sabem que algumas galáxias em seus estágios mais incipientes tinham halos que estavam muito mais estendidos do que se acreditava e que podem consistir de material utilizado para o crescimento da galáxia".
