Mars (zbiorczo)

[Orionid]

NASA wstrzyma tymczasowo wysyłanie poleceń do sond marsjańskich
19.07.2017

Pod koniec lipca amerykańska agencja kosmiczna NASA wstrzyma na ponad tydzień wysyłanie poleceń do swoich trzech sond orbitalnych i dwóch łazików marsjańskich. Winne jest Słońce, które będzie zakłócało transmisje.

Przyczyną takiej decyzji NASA jest obecne położenie Marsa na orbicie wokół Słońca, prawie bezpośrednio za gwiazdą - patrząc z Ziemi. Naukowcy spodziewają się w związku z tym znacznego pogorszenia jakości sygnałów komunikacyjnych i chcą uniknąć sytuacji, w której sonda niepoprawnie zrozumiałaby jakąś komendę. Polecenia do marsjańskich sond nie będą więc przesyłane od 22 lipca do 1 sierpnia.
 
Z kolei łączność związana z przesyłaniem danych przez sondy na Ziemię - w tym telemetria - będzie utrzymywana, aby centrum kontroli lotu miało bieżący obraz stanu sond i łazików. W tej sytuacji jeśli jakieś informacje ulegną utraceniu, dane zostaną retransmitowane później.
 
Mars znajduje się w pozycji za Słońcem regularnie co 26 miesięcy. Wtedy Ziemia, Słońce i planeta są w ustawione w jednej linii. Taka sytuacja nazywana jest przez astronomów koniunkcją (złączeniem). Przy czym zwykle nie jest to konfiguracja, w której tarcza słoneczna dokładnie przesłaniałaby planetę. Jednak, dla jakości komunikacji radiowej z sondami kosmicznymi problem powstaje już gdy planeta jest blisko tarczy słonecznej. Przyczyną jest słoneczna korona, która rozciąga się daleko od powierzchni Słońca. Korona słoneczna składa się z gorącego, zjonizowanego gazu, który może zakłócać przechodzące przez niego fale radiowe.
 
Zespoły kontroli lotu sond i łazików marsjańskich od kilku tygodni przygotowują się do wstrzymania komunikacji 22 lipca. Polecenia na okres przerwy w komunikacji zostaną wysłane wcześniej, a marsjańskie pojazdy będą wykonywały zaplanowane wcześniej zadania.
 
Dla sondy Mars Odyssey będzie to ósma koniunkcja Marsa ze Słońcem, dla łazika Opportunity siódma, dla sondy Mars Reconnaissance Orbiter szósta, dla łazika Curiosity trzecia, a dla sondy MAVEN druga. Jak podkreślają pracownicy NASA, wszystkie te sondy są już weteranami takich koniunkcji, zatem wiadomo czego można się spodziewać. (PAP)

http://naukawpolsce.pap.pl/aktualnosci/news,415032,nasa-wstrzyma-tymczasowo-wysylanie-polecen-do-sond-marsjanskich.html
https://www.jpl.nasa.gov/news/news.php?feature=6895

[kanarkusmaximus]

Fajne nagranie o serii zdjęć Marsa z HST:

[Orionid]

W tym roku minie 140 lat od odkrycia tego księżyca.

Over the course of 22 minutes, Hubble took 13 separate exposures, allowing astronomers to create a time-lapse video showing the diminutive moon's orbital path. The Hubble observations were intended to photograph Mars, and the moon's cameo appearance was a bonus. (...)

About two weeks after the Apollo 11 manned lunar landing on July 20, 1969, NASA's Mariner 7 flew by the Red Planet and took the first crude close-up snapshot of Phobos. On July 20, 1976 NASA's Viking 1 lander touched down on the Martian surface. A year later, its parent craft, the Viking 1 orbiter, took the first detailed photograph of Phobos, revealing a gaping crater from an impact that nearly shattered the moon.

?Phobos was discovered by Asaph Hall on August 17, 1877 at the U.S. Naval Observatory in Washington, D.C., six days after he found the smaller, outer moon, named Deimos. Hall was deliberately searching for Martian moons.

https://phys.org/news/2017-07-hubble-martian-moon-orbiting-red.html

[Orionid]

Nocą na Marsie pada śnieg
BY MATEUSZ OLSZEWSKI ON 24 SIERPNIA 2017

(...) Zespół pod kierownictwem Aymeric Spiga z Uniwersytetu Piotra i Marii Curie w Paryżu, połączył dane dostarczone przez różne misje na powierzchnię Marsa jak i orbiterów Mars Global Surveyor i Mars Reconnaissance Orbiter by stworzyć nowy model atmosferyczny. Następnie przeprowadzone zostały symulacje numeryczne warunków pogodowych, regionów Marsa w których występuje zachmurzenie. Ich wyniki wykazały, że w tych obszarach mogą występować konwekcyjne burze śnieżne.

“W naszych symulacjach konwektywne burze śnieżne występują tylko podczas nocy marsjańskich i wynikają z niestabilności atmosferycznej spowodowanej radiacyjnym chłodzeniem przez zamarznięte cząsteczki wody. Generuje to silne prądy konwekcyjne pomiędzy dolną a górną warstwą chmur, czego rezultatem są obfite opady śniegu.” (...)

http://kosmonauta.net/2017/08/noca-na-marsie-pada-snieg/
https://phys.org/news/2017-08-mars-weather-cloudy-chance-nighttime.html

[Nemhain]

Edit.

[Orionid]

New Gravity Map Suggests Mars Has a Porous Crust
Sept. 13, 2017


A new map of the thickness of Mars’ crust shows less variation between thicker regions (red) and thinner regions (blue), compared to earlier mapping. This view is centered on Valles Marineris, with the Tharsis Montes near the terminator to its west. The map is based on modeling of the Red Planet’s gravity field by scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The team found that globally Mars’ crust is less dense, on average, than previously thought, which implies smaller variations in crustal thickness.
Credits: NASA/Goddard/UMBC/MIT/E. Mazarico

NASA scientists have found evidence that Mars’ crust is not as dense as previously thought, a clue that could help researchers better understand the Red Planet’s interior structure and evolution.

A lower density likely means that at least part of Mars’ crust is relatively porous. At this point, however, the team cannot rule out the possibility of a different mineral composition or perhaps a thinner crust.

“The crust is the end-result of everything that happened during a planet’s history, so a lower density could have important implications about Mars’ formation and evolution,” said Sander Goossens of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Goossens is the lead author of a Geophysical Research Letters paper describing the work.

The researchers mapped the density of the Martian crust, estimating the average density is 2,582 kilograms per meter cubed (about 161 pounds per cubic foot). That’s comparable to the average density of the lunar crust. Typically, Mars’ crust has been considered at least as dense as Earth’s oceanic crust, which is about 2,900 kilograms per meter cubed (about 181 pounds per cubic foot).

The new value is derived from Mars’ gravity field, a global model that can be extracted from satellite tracking data using sophisticated mathematical tools. The gravity field for Earth is extremely detailed, because the data sets have very high resolution. Recent studies of the Moon by NASA’s Gravity Recovery and Interior Laboratory, or GRAIL, mission also yielded a precise gravity map.

The data sets for Mars don’t have as much resolution, so it’s more difficult to pin down the density of the crust from current gravity maps. As a result, previous estimates relied more heavily on studies of the composition of Mars’ soil and rocks.

“As this story comes together, we’re coming to the conclusion that it’s not enough just to know the composition of the rocks,” said Goddard planetary geologist Greg Neumann, a co-author on the paper. “We also need to know how the rocks have been reworked over time.”

Goossens and colleagues started with the same data used for an existing gravity model but put a new twist on it by coming up with a different constraint and applying it to obtain the new solution. A constraint compensates for the fact that even the best data sets can’t capture every last detail. Instead of taking the standard approach, known to those in the field as the Kaula constraint, the team created a constraint that considers the accurate measurements of Mars’ elevation changes, or topography.

“With this approach, we were able to squeeze out more information about the gravity field from the existing data sets,” said Goddard geophysicist Terence Sabaka, the second author on the paper.

Before taking on Mars, the researchers tested their approach by applying it to the gravity field that was in use before the GRAIL mission. The resulting estimate for the density of the moon’s crust essentially matched the GRAIL result of 2,550 kilograms per meter cubed (about 159 pounds per cubic foot).

From the new model, the team generated global maps of the crust’s density and thickness. These maps show the kinds of variations the researchers expect, such as denser crust beneath Mars’ giant volcanoes.

The researchers note that NASA’s InSight mission — short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport — is expected to provide the kinds of measurements that could confirm their finding. This Discovery Program mission, scheduled for launch in 2018, will place a geophysical lander on Mars to study its deep interior.

https://www.nasa.gov/feature/goddard/2017/new-gravity-map-suggests-mars-has-a-porous-crust

[Orionid]

Obserwacje przekrojów geologicznych  w dolinie Aeolis Dorsa (rejon o największym stężeniu występowania rzek w przeszłości) wskazują ,  że zasoby wody zmieniały swój poziom, co świadczy o nieepizodycznym  występowaniu tam wody.

More evidence of water on Mars
New Geological Society of America Bulletin paper
September 18, 2017 Source: Geological Society of America


The dotted white arrow points to curved strata recording point bar growth and river migration. The boundaries of ancient valley walls are defined by textural and albedo changes and are also associated with lateral river migration. Stacked above the point bars and completely confined within the dotted white and black lines are topographically inverted river deposits outcropping as ridges (e.g., black arrow). In places (e.g., south of the dotted white arrow), the ridges run against the dotted boundaries, suggesting flow was once redirected along a valley wall.
Credit: B.T. Cardenas et al., Geological Society of America Bulletin

River deposits exist across the surface of Mars and record a surface environment from over 3.5 billion years ago that was able to support liquid water at the surface. A region of Mars named Aeolis Dorsa contains some of the most spectacular and densely packed river deposits seen on Mars.

These deposits are observable with satellite images because they have undergone a process called "topographic inversion." where the deposits filling once topographically low river channels have been exhumed in such a way that they now exist as ridges at the surface of the planet.

With the use of high-resolution images and topographic data from cameras on orbiting satellites, B.T. Cardenas and colleagues from the Jackson School of Geosciences identify fluvial deposit stacking patterns and changes in sedimentation styles controlled by a migratory coastline. They also develop a method to measure river paleo-transport direction for a subset of these ridges.

Together, these measurements demonstrate that the studied river deposits once filled incised valleys. On Earth, incised valleys are commonly cut and filled during falling and rising eustatic sea level, respectively.

Cardenas and colleagues conclude that similar falling and rising water levels in a large water body forced the formation of the paleo-valleys in their study area. Cross-cutting relationships are observed at the valley-scale, indicating multiple episodes of water level fall and rise, each well over 50 meters, a similar scale to eustatic sea level changes on Earth.

The conclusion that such large water level fluctuations and coastline movements were recorded by these river deposits suggests some long-term stability in the controlling, downstream water body, which would not be expected from catastrophic hydrologic events.

https://www.sciencedaily.com/releases/2017/09/170918123518.htm

[Orionid]

Nowe opracowanie zakłada , że utrzymywanie się w przeszłości zbiorników z wodą w okresach bardziej suchych mogły sprzyjać wybuchy metanu.

Explosive bursts of methane helped ancient Mars keep liquid water flowing, study finds
October 3, 2017 by Amina Khan, Los Angeles Times

(...) So here's the thing that's puzzled planetary scientists: Gale Crater's rocks bear evidence of liquid water on Mars during the Hesperian period, including lakes (perhaps protected by a layer of surface ice) and deltas. But that means these lakes and deltas persisted during a period that was markedly drier, with a thinner atmosphere less capable of sustaining liquid water. How do these two facts square up?

"Previous hypotheses have struggled to explain lake-forming climates that are both rare and long-lasting," Fairen wrote. "For example, volcanism and impacts can produce episodes of climate warming, but not of sufficiently long duration."

Now, lead author Edwin Kite, a planetary scientist the University of Chicago, and his colleagues say that after running climate models they've come up with an explanation: explosive bursts of methane. (...)

https://phys.org/news/2017-10-explosive-methane-ancient-mars-liquid.html
https://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo3033.html

[ekoplaneta]

Nowe opracowanie zakłada , że utrzymywanie się w przeszłości zbiorników z wodą w okresach bardziej suchych mogły sprzyjać wybuchy metanu.

Explosive bursts of methane helped ancient Mars keep liquid water flowing, study finds
October 3, 2017 by Amina Khan, Los Angeles Times

(...) So here's the thing that's puzzled planetary scientists: Gale Crater's rocks bear evidence of liquid water on Mars during the Hesperian period, including lakes (perhaps protected by a layer of surface ice) and deltas. But that means these lakes and deltas persisted during a period that was markedly drier, with a thinner atmosphere less capable of sustaining liquid water. How do these two facts square up?

"Previous hypotheses have struggled to explain lake-forming climates that are both rare and long-lasting," Fairen wrote. "For example, volcanism and impacts can produce episodes of climate warming, but not of sufficiently long duration."

Now, lead author Edwin Kite, a planetary scientist the University of Chicago, and his colleagues say that after running climate models they've come up with an explanation: explosive bursts of methane. (...)

https://phys.org/news/2017-10-explosive-methane-ancient-mars-liquid.html
https://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo3033.html

Ciekawe czy kiedykolwiek ta hipoteza uwalniania się klatratów metanowych na Marsie będzie mogła być w przyszłości udowodniona? Czy dawne złoża metanu mogłyby pozostawić jakieś ślady swej obecności w skałach?

[Orionid]

Ziemskie badania meteorytu z grupy Nakhlite pozwoliły ustalić , że na Marsie w czasie ok. 90 mln miało miejsce kilkukrotne uaktywnianie się wulkanu. 11 mln lat temu wskutek impaktu meteoryt został skierowany na trajektorię wiodącą ku Ziemi.
Źródło impaktu znajduje się  900 km od szczytu wulkanu Elysium Mons i jest zlokalizowane w odległości ponad 2000 km na północ od obecnej lokalizacji Curiosity.

Analysis of Martian meteorites has uncovered 90 million years' worth of new information about one of the red plan
October 4, 2017


Credit: University of Glasgow

Analysis of Martian meteorites has uncovered 90 million years' worth of new information about one of the red planet's volcanoes – and helped pinpoint which volcano the meteorites came from.

Geologists based in the UK and the USA have used advanced mass spectrometry techniques to learn more about the origins of six meteorites known as 'nakhlites' – pieces of Martian terrain which were blasted from the face of the red planet by an impact event 11 million years ago, then drifted through space before landing on Earth.

Nakhlite meteorites are the second most common type of Martian meteorites. Three of the meteorites were found in Antarctica, one in the USA, one in northwestern Africa, and one in Egypt.

Their findings, which show that the Martian volcano erupted at least four times over the course of 90 million years, appear in a new paper in the journal Nature Communications, published today (Wednesday 4 October).

Mars is home to the solar system's largest volcanoes, including Olympus Mons, which is over 21 kilometres high and over 600 kilometres across. Their imposing size is partially due to Mars' lack of tectonic plates. Unlike Earth, where shifting plates will eventually cut off volcanoes access to their supply of molten rock, Martian volcanoes stay in the same place, and can grow in size with each eruption as new layers of lava settle and cool on the volcanic flanks.

The team's new research uses radioisotopic dating techniques, common for determining the age and eruption rate of terrestrial volcanoes, to do the same thing for one Martian volcano. This is the first detailed analysis of growth rates in Martian volcanoes using Martian meteorites, and highlights significant differences in volcanic activity between the Earth and Mars.

The research was conducted by scientists at the Scottish Universities Environmental Research Centre, the Universities of Glasgow and St Andrews, the Lawrence Livermore National Laboratory, and the Natural History Museum in London.
Dr Benjamin Cohen, of the Scottish Universities Environmental Research Centre and the University of Glasgow's School of Geographical and Earth Sciences, is the paper's lead author.

Dr Cohen said: "We know from previous studies that the nakhlite meteorites are volcanic rocks, and the development of age-dating techniques in recent years made the nakhlites perfect candidates to help us learn more about volcanoes on Mars."

First, the team reconfirmed how long the meteorites had spent in space before reaching Earth, by measuring their exposure to cosmogenic radiation. They confirmed that all of the nakhlites had all been ejected into space together around 11 million years ago.

Then the researchers used a technique known as argon-argon geochronology to learn more about the age of the Martian volcanic samples. Using a noble gas mass spectrometer, they could measure the amount of argon built-up from natural radioactive decay of potassium, allowing them to determine how much time has passed since the volcano erupted.

Dr Cohen added: "We found that the nakhlites formed from at least four eruptions over the course of 90 million years. This is a very long time for a volcano, and much longer than the duration of terrestrial volcanoes, which are typically only active for a few million years.

"And this is only scratching the surface of the volcano, as only a very small amount of rock would have been ejected by the impact crater – so the volcano must have been active for much longer."

The team's research has also helped them narrow down the possibilities of exactly which Martian volcano their samples came from.

Dr Cohen added: "Previous studies had suggested several different candidate locations for the nakhlite source crater. However, only one of these locations identified so far matches our results for the age of the eruptions and the timing of impact ejection into space. This unnamed crater is situated on an area of gently sloping lava plains 900 km from the summit of the 12.6 km high Elysium Mons volcano, and is over 2000 km north of the present site of the NASA Curiosity rover.

"NASA has some wonderfully detailed satellite images of this crater. It is 6.5 km wide, and has preserved ejecta rays of debris. And we were able to see multiple horizontal bands on the crater walls – which indicating the rocks form layers, with each layer interpreted as a separate lava flow.

"This study has been able to provide a clearer picture into the history of the nakhlite meteorites, and in turn the largest volcanoes in the solar system."

The paper, titled 'Taking the pulse of Mars via dating of a plume-fed volcano', is published in Nature Communications.

Journal reference: Nature Communications
Provided by: University of Glasgow
https://phys.org/news/2017-10-analysis-martian-meteorites-uncovered-million.html

[ekoplaneta]

To niesamowite że meteoryty z grupy Nakhlite da się przyporządkować do konkretnego wulkanu  Mam tylko nadzieję, że tu nikt za bardzo się nie pomylił.

Poza tym przedmiotowe badania wskazują, że od ziemskiego okresu kredowego (era mezozoiczna) miała miejsce niejedna aktywność wulkaniczna na Czerwonej Planecie. Warto wspomnieć, że jeden w wulkanów Tharsis dymił ostatnio około 54 milionów lat temu

Ciekawe kiedy kolejny raz marsjański wulkan zadymi? 

[Orionid]

Takie wiadomości dostarczają argumentów na rzecz nieustannej badawczej aktywności na Marsie.

Poza tym zastanawiam się, czy nie powinny powstać regulacje ograniczające wstęp ewentualnym przyszłym tabunom kolonistów na  tereny o szczególnej wartości naukowej.

[ekoplaneta]

Jeśli już to ograniczyć tabuny imigrantów na Marsa. Bo jak zawleczemy tam życie mikro to będzie już po sprawie. Chyba że chodzi Ci Orionidzie o ochronę ewentualnych mikroskamieniałości 

[kanarkusmaximus]

To jest kwestia, nad którą najwcześniej raczej się będziemy zastanawiać za 40 lat. Raczej wciąż nie ma i szybko nie powstaną niezawodne systemy podtrzymywania życia,które zadziałają na Marsie.

heh, ale się robi off-top. Nie ma na to odpowiedniego wątku?

[Adam.Przybyla]

Ogolnie to istotnie problemu nie ma. Zycie, nawet jesli bysmy chcieli, dlugo by tam nie przetrwalo.
BTW, to sie chyba nadaje do watku "Mars zbiorczo". Z powazaniem
                       Adam Przybyla