Astronomija i Svemirska Istrazivanja

[McLeod]

Naravno da se odavno zna za oblik magnetosfere. Ali tek su skorasnje sonde sa svojim osetljivim instrumentima pokazale da je ona jos veca.

 

Isto kao sto se i Suncev sistem prostire mnogo dalje nego sto smo mislili, ali je taj uticaj prakticno zanemarljiv za ono o cemu se diskutovalo.

[HAMMER]

 

[HAMMER]

 

[Kronostime]

Elone, ubrzaj te planove za Mars - planiram da se preselim!

[Klotzen]

UAE su lansirali svoju misiju na Mars. U pitanju je prvi satelit koji će istraživati vreme i klimu na Marsu. Imaju i svoj sajt na kom će moći da se prate pojedini delovi putovanja :

 

https://www.emiratesmarsmission.ae/live/

 

[HAMMER]

31 jul sledeci bitan datum

[Klotzen]

Pre neki dan i Kinezi su poslali sondu sa robotom na Mars. Sonda bi trebalo da ostane u orbiti Marsa a robot će biti poslan na Mars da analizira površinu crvene planete. Juče je objavljena slika koju je sonda napravila 1,5 miliona km od zemlje :

 

 

Na slici su zemlja i mesec.

[Klotzen]

Danas je i SAD lansirao novu misiju na Marsu. Njihova misija ima zadatak da ispita da li je bilo života na Marsu i uslove leta u atmosferi Marsa. Prvi zadatak radiće rover :

 

 

A za letenje je zadužen helikopter :

 

 

Biće prilična gužva u orbiti Marsa sledeće godine :)

[C.F.]

[C.F.]

 

[Amigo]

3 hours ago, Klotzen said:

Danas je i SAD lansirao novu misiju na Marsu. Njihova misija ima zadatak da ispita da li je bilo života na Marsu i uslove leta u atmosferi Marsa. Prvi zadatak radiće rover :

 

A za letenje je zadužen helikopter :

 

 

Biće prilična gužva u orbiti Marsa sledeće godine 🙂

 

Pitanje je da li helikopter uopste moze da leti na Marsu jer je atmosferski pritisak samo 6-7 milibara, prema 1000 na Zemlji.

[C.F.]

5 minutes ago, Amigo said:

 

Pitanje je da li helikopter uopste moze da leti na Marsu jer je atmosferski pritisak samo 6-7 milibara, prema 1000 na Zemlji.

 

Nista bez rizika, pa cak i kad kosta 80 miliona.

 

 

The helicopter, named Ingenuity, weighs in at only four pounds and is less than two feet tall. Powered by solar panels with lithium ion batteries, Ingenuity can fly up to 90 seconds at a stretch. Its rotors spin about eight times faster than a helicopter on Earth. 

The $80 million helicopter is viewed as the "high risk-high reward" part of the mission with the first test flight scheduled for spring of 2021. 

 

izvor: https://www.azcentral.com/story/news/local/arizona-science/2020/07/26/mars-mission-2020-and-perseverance-rover-8-things-know/5467879002/

[Klotzen]

Ako to mi znamo onda to znaju i oni koji su projektovali helikopter. Definitivno će pored rovera biti potrebna i leteća vozila kada jednom krene misija sa ljudskom posadom. Što pre krenu da testiraju pre ćemo imati sva potrebna znanja da projektujemo letelicu za Mars koja će biti 100% pouzdana.

[Veshtodel]

Oktriven fosfin u atmosferi Venere za koji se veruje da bi mogao biti biološkog porekla, pošto ga na Zemlji proizvode anaeorobni organizmi kojima nije potreban kiseonik.

 

Podsetimo da je u ranoj istoriji planete Zemlje bilo vrlo malo kiseonika i da je većina tadašnjih organizama radila bez kiseonika koristeći procese slične fermentaciji, sve dok cijanobakterije nisu počele da ispuštaju kiseonik kao nus proizvod i tako dovele do Velike Oksidacije zbog kojih mi danas postojimo.

 

Doduše postoji mogućnost da je ovaj fosfin nastao nekim do sada nama nepoznatim fizičkim i hemijskim procesima koji se dešavaju u atmosferi Venere, a koji znači nisu produkt nekih anaerobnih organizama. U svakom slučaju, planiraju se dalja istraživanja.

 

Vesti o fosfinu na Veneri ovde:

 

https://www.space.com/phosphine-venus-clouds-chemical-explained.html

 

http://astrobiology.com/2020/09/phosphine-on-venus-cannot-be-explained-by-conventional-processes.html

[Asterion]

On 9/15/2020 at 7:01 AM, Veshtodel said:

Oktriven fosfin u atmosferi Venere za koji se veruje da bi mogao biti biološkog porekla, pošto ga na Zemlji proizvode anaeorobni organizmi kojima nije potreban kiseonik.

 

Podsetimo da je u ranoj istoriji planete Zemlje bilo vrlo malo kiseonika i da je većina tadašnjih organizama radila bez kiseonika koristeći procese slične fermentaciji, sve dok cijanobakterije nisu počele da ispuštaju kiseonik kao nus proizvod i tako dovele do Velike Oksidacije zbog kojih mi danas postojimo.

 

Doduše postoji mogućnost da je ovaj fosfin nastao nekim do sada nama nepoznatim fizičkim i hemijskim procesima koji se dešavaju u atmosferi Venere, a koji znači nisu produkt nekih anaerobnih organizama. U svakom slučaju, planiraju se dalja istraživanja.

 

Vesti o fosfinu na Veneri ovde:

 

https://www.space.com/phosphine-venus-clouds-chemical-explained.html

 

http://astrobiology.com/2020/09/phosphine-on-venus-cannot-be-explained-by-conventional-processes.html

 

#Anaerobnim organizmima je potreban kiseonik. Npr. jedna molekula vode ima jedan kiseonik.

 

##radila je vrlo loša reč pa makar to bila u italic.

 

###Ti procesi su slični fermentaciji samo u tome što ne koriste O2 kao terminalni akceptor elektrona. Fermentacija je baš loša što (kad se uporedi se nekima anaerobnima respiracijama) se tiče generacije ATP.

 

 

U glavnom...moje lično mišljenje je, da če čovečanstvo kao prve živote izvan Zemlje otkriti mikrobe. Ubeđen sam, da postoje mikrobi na drugim planetima, jer su vrlo prilagodljiv. Guglajte malo  podatke/otkriča/studije sa Zemlje (razna ekstremna područja ala gejziri, slana/kisela jezera, okoline blizu vulkana, okoline zatvorenih nuklearka/rudnika urana, područja sa večitim ledom,...). 

 

 

 

 

 

[Darth Bane]

Najbolji kandidati za pronalazenje zivota i to onog malo kompleksnijeg su Jupiterovi sateliti Evropa, Ganimed i Kalisto. Smatra se da svi imaju podzemne okeane vode. Na zalost to necemo saznati najmanje do oko 2030 godine kada se ocekuje naredna misija prema Jupiterovom sistemu (lansiranje oko 2022-23 dolazak tamo posle 2030). A eventualno spustanje neke sonde na nekom od tih satelita najverovatnije nakon 2040. 

[Asterion]

Voda je bitan faktor ali ne treba, da je glavni....hoču reči koliko je vode (odnosno water activity ...aw) u stvari potrebne za život...

 

Representative idealized cross section of Earth’s crust showing the diversity of extreme environments and their approximate location

 

 

 

Na gornjoj slici su primeri (na molekularnom nivoju) kako se mikrobi 'bore' odnosno kako su se prilagodili na ekstremne uvete na Zemlji.

 

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Can Life Originate, Evolve, or Survive on Other Planetary Bodies?

Different classification schemes have been published to describe planetary bodies based on their ‘habitability’ (e.g., Lammer et al., 2009; Noack et al., 2016; Schulze-Makuch et al., 2017). Several studies have also demonstrated the growth of microorganisms under lab-simulated planetary conditions, including Mars-like (Nicholson et al., 2013; Schuerger and Nicholson, 2016; Fajardo-Cavazos et al., 2018) and Enceladus-like (Taubner et al., 2018) conditions. In this context, defining the boundary limits of life on Earth is a crucial step in identifying the conditions likely to originate or support life on other planetary bodies. Therefore, studies on the limits of life are important to understand four areas: (1) the potential for panspermia, (2) forward contamination due to human exploration ventures, (3) planetary colonization by humans, and (4) the exploration of extinct and extant life. In this review, we outline the physical and chemical boundary conditions of Earth’s environments and those of life on Earth and compare them to the conditions observed on other planetary bodies in order to discuss whether life could originate, evolve, or survive elsewhere in our solar system and beyond.

Similar to Earth, other planetary bodies might have different environments with varying ranges for each parameter. Since our knowledge of individual niches or habitats is extremely limited for other planetary bodies, we considered the range of each parameter (temperature, salinity, pH, and pressure) across three planetary layers: (1) atmosphere, (2) surface, and (3) subsurface (Table 5). Many planetary bodies studied thus far have the potential for extinct or extant life, based on our knowledge of life on Earth. Depending on the planetary body, different (poly)extremophiles could persist. For example, halopsychrophiles might be able to persist on Titan, Ceres, and Europa, which likely have saline subsurface oceans (Grindrod et al., 2008; Zolotov and Kargel, 2009; Neveu and Desch, 2015), and also on Mars which could have Cl-rich subsurface brines (Clifford et al., 2010; Jones et al., 2011). These lifeforms would also need to withstand high pressures. For example, the hydrostatic pressure of the subsurface ocean at Titan ranges from 140 to 800 MPa (Sohl et al., 2014). While such pressures are beyond the range of the most extreme cultured piezophile on Earth (Thermococcus piezophilus, Pmax = 125 MPa) (Dalmasso et al., 2016), microorganisms have successfully been exposed to pressures up to 2,000 MPa and found to be metabolically active in fluid inclusions within type-IV ice (Vanlint et al., 2011). Based on these observations it is possible that other planetary bodies may be within reach for Earth-based life (Table 5), including Enceladus (Pmax = 50 MPa; Hsu et al., 2015) and Europa (Pmax = 30 MPa; Muñoz-Iglesias et al., 2013).

 

 

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The atmospheres of some planetary bodies could potentially harbor life as well. In particular, the upper-to-middle cloud layers of Venus (0–60°C; pH∼0) might be suitable for thermo- or psychro-acidophilic microorganisms (Table 4). Titan also has a dense atmosphere, but it is extremely cold (-183 – -78°C) and life on Earth can only metabolize at temperatures greater than -20°C (Rivkina et al., 2000). Other planetary bodies presented in Table 5 have transient or tenuous atmospheres that have extremely low pressures and likely cannot support life. In comparison, on Earth, microorganisms have been observed and cultured from the upper atmosphere, although stresses such as UV-C radiation, low temperatures, and oxidants make it difficult to survive (DasSarma and DasSarma, 2018). Microorganisms, in particular psychrophiles, with the capability of biofilm formation, clumping, and repair systems are more likely to tolerate Earth’s atmospheric conditions (DasSarma and DasSarma, 2018). Similar strategies may be needed on other planetary bodies.

The surface of other planetary bodies, such as Ceres, Europa, and Mars, experience high levels of radiation, and thus, may be unsuitable to support life. UV radiation is damaging for Earth-based life, and several studies have shown that there is a 99% loss in viability for microorganisms placed under Mars-like surface conditions, with UV-C as the most harmful source (Schuerger et al., 2003). However, shielding from UV-C radiation increases the chance of survival and includes shielding by atmospheric dust or burial (Barbier et al., 1998; Mancinelli and Klovstad, 2000; Cockell et al., 2002, 2005; Schuerger et al., 2003; Hansen et al., 2009; Johnson et al., 2011). Shielding is also necessary against charged particle radiation and can be achieved by burial at only centimeter depths below the surface. Indeed, the harsh radiation exposed to Europa’s surface inside the Jovian magnetosphere is predicted to only penetrate about 1–20 cm below the surface of Europa, as modeled by Nordheim et al. (2018).

Solar and galactic cosmic rays (high-energy particles with energies from 10 MeV to >10 GeV) present challenges to life on the surface and near-surface of Mars and other planetary bodies. However, any subsurface aquifer deeper than a few meters would be protected from damaging radiation. Dartnell et al. (2007) calculated the galactic cosmic ray dosage rates and the corresponding survival times (which they defined as a million-fold decrease in cell number) of characteristic microbes at different depths in Mars’s subsurface. At the surface, E. coli has a survival time of 1,200 years, while at 20-m depth, that survival time jumps to 1.5 × 108 years. Compared to E. coli, D. radiodurans has survival times an order of magnitude longer. These survival times are, in fact, lower limits in light of recent measurements by the Radiation Assessment Detector onboard the Mars Science Laboratory (Hassler et al., 2014), which found that the actual dose rate at Gale Crater (76 mGy year-1) is a factor of 2 lower than that modeled by Dartnell et al. (2007).

With respect to cosmic rays, early Mars would have provided more favorable environments: Mars’s ancient dynamo may have produced a global magnetic field on the order of that of the present-day Earth (Weiss et al., 2008), and a thicker atmosphere would have also provided significantly impeded a flux of high-energy particles. Ehresmann et al. (2011) found that, with an atmosphere 100 times as thick, the dose rate at the surface decreases to ∼0.3–20% of its present-day value.

In addition to radiation, the surface of other planetary bodies is generally extremely cold. The minimum estimated temperature all planetary bodies listed in Table 5, except for Venus, ranges from -138°C (Mars) to -233°C (Enceladus) while the maximum estimated temperature ranges from -179°C (Titan) to 30°C (Mars). In accordance, the average temperature of satellites that are potential analogs to Earth is much less than -5°C, with many satellites likely experiencing wide temperature variation (Reid et al., 2006). This indicates the physiology of radiation-tolerant psychrophiles is important for understanding the potential of life on the surface of other planetary bodies, such as the production of a fibril network, cell aggregation, and cold shock proteins (Reid et al., 2006).

This suggests the subsurface is one of the most important locations in the search for extinct and extant extraterrestrial life (Jones et al., 2018). On Earth alone, the subsurface is estimated to house 50–87% of the Earth’s microorganisms (Kallmeyer et al., 2012; Magnabosco et al., 2018). The subsurface of other planetary bodies is potentially warmer than the surface and atmosphere (Table 5), influenced by geothermal processes [e.g., on Mars (Jones et al., 2011)], thermal convection [e.g., on Enceladus and Titan (Mitri and Showman, 2008)] and radiolysis [e.g., on Mars (Dzaugis et al., 2018)]. Several planetary bodies (Enceladus, Titan, Ceres, and Europa) likely have subsurface oceans, and Mars could potentially have a limited supply of groundwater (Clifford et al., 2010). Potential communities in these extraterrestrial subsurface environments are unlikely to be supported by surface exports of organic carbon like on our planet (Kallmeyer et al., 2012), but rather by in situ production fueled by H2 and abiotic CH4. The abiotic production of H2 can occur through a variety of mechanisms, including the radiolysis of water (Lin et al., 2005; Dzaugis et al., 2018) and serpentinization at both high and low temperatures (Neubeck et al., 2011; McCollom, 2016).

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[Darth Bane]

Sto se Galilejevih satelita tice, navodno postojanje unutrasnjih okeana skrivenih ispod debele kore leda je jos uvek spekulativno. To je jos uvek samo hipoteza bazirana na postojanju magnetskog polja oko Evrope i Ganimeda te se pretpostavlja da je uzrok tome neki tecni provodnik elektriciteta od kojih je navodno slana voda najverovatnija. Ali sta ako se ipak radi o tankom uzareno - tecnom sloju Fe-Ni kao sto je slucaj kod nase planete Zemlje? Onda bi i verovatnoca pronalazenja zivota na Evropi i Ganimedu bila daleko manja. 

Zato bi mozda trebalo se usredsrediti na Titan i tamo sto pre poslati jednu letelicu koja bi obavezno imala modul za spustanje na tlo Titana.

[Asterion]

22 hours ago, Asterion said:

Voda je bitan faktor ali ne treba, da je glavni....hoču reči koliko je vode (odnosno water activity ...aw) u stvari potrebne za život...

 

Representative idealized cross section of Earth’s crust showing the diversity of extreme environments and their approximate location

 

 

 

Na gornjoj slici su primeri (na molekularnom nivoju) kako se mikrobi 'bore' odnosno kako su se prilagodili na ekstremne uvete na Zemlji.

 

 

 

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Ovde sam malo bio peksav...pa da dodam još nešto o aw:

1. Šta je water activity (aw) :

 

 

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https://i.ytimg.com/vi/PYLkt9kZHg4/maxresdefault.jpg

 

Water activity, or aw, is a measure of the free moisture in a product and is defined as the ratio of vapor pressure of a substance to that of pure water at a specified temperature.

Water activity’s usefulness a food quality and safety measurement was suggested when it was obvious water content (% or total moisture) could not adequately account for microbial growth fluctuations because the amount of water present often does not adequately characterize the capacity to find water or to limit its escaping tendency.

The water activity of a food product describes the degree to which water is “bound” in the food, and its availability to participate in chemical/biochemical reactions and growth of microorganisms.  Hence, texture, non-enzymatic browning reactions, enzymatic activity, lipid oxidation, and other aspects of foods may be influenced by manipulation of aw levels.

The amount of water removed from or added to a food depends on the nature and amount of water-soluble substances (water binding capacity) present in the product.

 

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Water activity is a better index for microbial growth that water content.

Water activity better predicts the growth of microorganisms because microorganisms can only use available water, which differs considerably depending on the solute.  On average, ions bind the most water, whereas polymers bind the least water; sugars and peptides fall into an intermediate position.  At the same molecular concentration, salt lowers the water activity more than sugar.

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2.Granice za mikrobe (bar bi morale biti; Zašto bar bi morale biti? Vidi dolje, pod 3.):

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Postoji još definicija aw gde su upotrebljava hemijski potencial.

 

 

3. U članku o život na drugim planetima kroz prizmu ekstremofila govora je i o water activity:

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As discussed in this review below, water activity appears to be the single key parameter controlling the biospace of Earth’s life, and numerous other parameters limiting life (e.g., temperature and salinity) are, in fact, acting on the availability of water. At the ecosystem level, water can indirectly influence the variation of key physicochemical conditions, which in turn controls microbial community composition and diversity, profoundly influencing geobiochemical cycling (sensu Shock and Boyd, 2015).

 

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On the nano- and micro-scale level, the two most important factors are likely water activity and pH, which influence the chemiosmotic, energy-generating gradient at the cell level (Lane et al., 2010; Lane and Martin, 2012). 

 

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The ionic composition can significantly influence water activities, especially in the presence of high concentrations chaotropic salts, like in the athalassic deep-sea hypersaline anoxic basins of the Mediterranean Sea (Yakimov et al., 2015). In addition, water availability in terrestrial saline environments is further influenced by precipitation rates relative to evaporation, resulting in increasing concentration of salts (Finlayson et al., 2018).

 

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Many microorganisms in saline environments must also adapt to low water activity (the mole fraction of water) and increased radiation (discussed in section “Radiation”). Although salts can lower the freezing point of water, saturated salt solutions have low water activity. Water activity is the only other parameter, aside from pH and salinity, that some microorganisms can regulate through the production of metabolites capable of storing or attracting water (e.g., proteins and polysaccharides from EPS) (Frösler et al., 2017). The theoretical water activity minima for halophilic archaea and bacteria is 0.611 aw while it is 0.632 aw for fungi (Stevenson et al., 2015). In comparison, the water activity of NaCl saturated solutions is estimated to be 0.755 aw while pure water is 1 aw (Hallsworth et al., 2007; Stevenson et al., 2015).

 

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The theoretical water activity limit has been surpassed by microbial life. When there are high concentrations of the chaotropic MgCl2 or CaCl2, the water activity is lowered even more (e.g., 0.3 aw for a saturated MgCl2 solution). For example, environmental surveys reported microbial communities in the brines of two athalassic deep-sea hypersaline anoxic basin (DHAB), Discovery (MgCl2 ≥ 5 M, T = 14.5°C) (Van Der Wielen et al., 2005) and Kryos Basin (saturated MgCl2, ∼0.4 aw, T = 16.5°C) (Alcaide et al., 2015; Steinle et al., 2018), both located in the Mediterranean Sea. The Kryos Basin microbial community, located in the brine, consisted of active sulfate-reducers, with sulfate reduction reaching up to 460 μmol/kg-day (Steinle et al., 2018). In contrast to the DHABs, microbial life has yet to be shown to exist in a CaCl2-dominated brine with up to 474 g/L total dissolved salts (Don Juan Pond, Antarctica) (Oren, 2013). This is likely due to both extreme temperature and salinity conditions, as Don Juan Pond is an unfrozen lake (pH 4.6) with an average depth of 11 cm and temperatures reaching below -36°C (Tmax ∼ 20°C) (Torii et al., 1981; Samarkin et al., 2010; Dickson et al., 2013). The estimated water activity in Don Juan Pond is likely below 0.45 aw (Oren, 2013) but could be between 0.28 aw (25°C) to 0.61 aw (–50°C), as estimated for a CaCl2-dominated brine with antarcticite (CaCl2⋅6H2O) precipitation (Toner et al., 2017).

 

 

Zamislite koliko je to malo vode... npr. ovi keksi:

https://s.yimg.com/aah/blaircandy/original-animal-crackers-2-12oz-box-57.jpg

 

 

imaju aw oko 0.3

izvor

[Prijatelj Mitar]

Naučnici koji proučavaju crnu rupu dobitnici Nobelove nagrade za fiziku

 

http://rs.n1info.com/SciTech/a657639/Naucnici-koji-proucavaju-crnu-rupu-dobitnici-Nobelove-nagrade-za-fiziku.html

 

Po meni nezasluzeno. Onda su Nobela zasluzili i gradjani Srbije koji proucavaju crnu rupu svakog jutra kada pogledaju u svoj novcanik.

 

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Salim se. Crne rupe su nesto sto me oduvek fascinira. Skoro sam procitao "Crne rupe i bebe Vaseljene". Tesko da cemo ikad dobiti sve odgovore u vezi sa njima...

[bohumilo]

To da samo da nije nezasluzeno, nego je sir Rodzer takva naucna i kulturna velicina i legenda da je ovde tacnije reci da je on dodeljen Nobelovoj nagradi, pre nego obrnuto.

[Klotzen]

Juče su Kinezi lansirali misiju na mesec koja bi trebala da bude interesantnija za praćenje. Plan je da sonda pokupi oko 2kg materijala sa površine i sa dubine od 2m i da to vrati na zemlju. Očekuje se da bi mogla da se vrati polovinom decembra. Nadam se da kinezi neće biti škrti sa informacijama jer im je u interesu da se malo pohvale a i da mi imamo šta da gledamo na ovu temu.

 

Evo jedne animacije od minut i po koja objašnjava plan misije :