The Astronomy Thread

[Flinn]

https://mars.nasa.gov/news/9252/nasa...jezero-crater/

Can't help but feel this is a bit of a disappointment. NASA expected to find (sedimentary) lake deposits at the bottom of Jezero crater. Sedimentary rock might tell us more about the Mars environment as it was when there was still running water. However, it only found igneous rock (produced by volcanic activity below or above the (then) surface). If sedimentary rock ever existed, it must have eroded away by dust-laden wind.

Honestly, I was not expecting any positive result in the upper strata regarding possible "fossiles" or even the presence of sedimentary deposits; not a case that the Nasa is fully relying on the reclamation of those samples (the drilled ones I mean) to give a sure answer to the question if there ever was life on Mars. We have to be patient and wait for a decade still, if not more. Anyways, not all is lost, radar scanning (down to 15 mt) has shown multiple strata of volcanic rocks which are interrupted by (supposedly) sedimentary deposits.

It is also interesting to notice that there's controversy about the "erosion" effect: in fact Mars has a very thin atmosphere and a relatively small size, both elements that negatively impact the possible speed and strength of wind (averagely is very slow, only in rare cases it can get up to peaks of 50 m/s, 180 km/h, roughly 100 kn, and that starts those global storms): the usual movie tempests we see in many movies are pretty fictional, plenty of equipment has been brought there and the hasn't been any real damage, only some issues with dust deposits on solar panels (such as it happened with Insight). Anyways, a small drop of water can drill a hole in a rock over the time, and Mars wind had billions of years to work on removing those upper sediments.

[Muizer]

It is also interesting to notice that there's controversy about the "erosion" effect: in fact Mars has a very thin atmosphere and a relatively small size, both elements that negatively impact the possible speed and strength of wind (averagely is very slow, only in rare cases it can get up to peaks of 50 m/s, 180 km/h, roughly 100 kn, and that starts those global storms): the usual movie tempests we see in many movies are pretty fictional, plenty of equipment has been brought there and the hasn't been any real damage, only some issues with dust deposits on solar panels (such as it happened with Insight). Anyways, a small drop of water can drill a hole in a rock over the time, and Mars wind had billions of years to work on removing those upper sediments.

It is also assumed it lost much of its atmosphere, is it not? Wind erosion may have been more severe in the past.

[Flinn]

It is also assumed it lost much of its atmosphere, is it not? Wind erosion may have been more severe in the past.

Yes indeed, but as I said there's controversy even on that.. it is believed by many that the evaporation of liquid water on the surface and the dissipation of the atmosphere have gone hand in hand, so to say. However, even on Earth erosion takes million of years, and we have stronger winds, rain, snow, etc.. Mars' dry thin atmosphere makes erosion a very slow process, but again it had billions of years. In any case if not for the slow erosion it would have had not sense at all to search for past life's evidences, after like 2,5 (or more) billions of years.

[skh1]

A splooge of recent James Webb Telescope videos

[skh1]

The sound of a black hole

Since 2003, the black hole at the center of the Perseus galaxy cluster has been associated with sound. This is because astronomers discovered that pressure waves sent out by the black hole caused ripples in the cluster’s hot gas that could be translated into a note – one that humans cannot hear some 57 octaves below middle C. Now a new sonification brings more notes to this black hole sound machine. This new sonification – that is, the translation of astronomical data into sound – is being released for NASA’s Black Hole Week this year. In some ways, this sonification is unlike any other done before […] because it revisits the actual sound waves discovered in data from NASA's Chandra X-ray Observatory. The popular misconception that there is no sound in space originates with the fact that most of space is essentially a vacuum, providing no medium for sound waves to propagate through. A galaxy cluster, on the other hand, has copious amounts of gas that envelop the hundreds or even thousands of galaxies within it, providing a medium for the sound waves to travel.
In this new sonification of Perseus, the sound waves astronomers previously identified were extracted and made audible for the first time. The sound waves were extracted in radial directions, that is, outwards from the center. The signals were then resynthesized into the range of human hearing by scaling them upward by 57 and 58 octaves above their true pitch. Another way to put this is that they are being heard 144 quadrillion and 288 quadrillion times higher than their original frequency. (A quadrillion is 1,000,000,000,000,000.) The radar-like scan around the image allows you to hear waves emitted in different directions. In the visual image of these data, blue and purple both show X-ray data captured by Chandra.

New NASA Black Hole Sonifications with a Remix | NASA

[Flinn]

https://mars.nasa.gov/news/9252/nasa...jezero-crater/

Can't help but feel this is a bit of a disappointment. NASA expected to find (sedimentary) lake deposits at the bottom of Jezero crater. Sedimentary rock might tell us more about the Mars environment as it was when there was still running water. However, it only found igneous rock (produced by volcanic activity below or above the (then) surface). If sedimentary rock ever existed, it must have eroded away by dust-laden wind.

Perseverance finds organic matter treasure on Mars.

Now, let's go in order. First I'm honestly shocked that CNN uses the term "organic matter", because it is not. Looks like they quoted a Nasa scientist, but I doubt that Mr Farley would have used that term. However, what Perseverance found are "organic molecules", or "the building blocks of life, such as carbon, hydrogen and oxygen, as well as nitrogen, phosphorous and sulfur." In other words, the news here is that Perseverance actually found and dug into sedimentary rocks (hence why I quotes Muizer's previous post) and that they found some molecules which might have been created by "life". Anyways: "Not all organic molecules require life to form because some can be created through chemical processes."

All in all that's the most basic discovery possible related to past life, we still have some hope when the samples will be send back, to find some fossilized bacteria or the like (that would definitely be the proof, since actually organic molecules can be found on comets as well and life hasn't certainly developed on them).

I'm not optimist to be honest, there's still a chance some basic forms of bacteria have evolved (looks like the oldest fossilized bacteria on Earth are like 3.45 billions of years), but my sensation is that we won't find anything like that on the surface of Mars.

[Flinn]

Nasa's DART mission hits asteroid.

“DART’s success provides a significant addition to the essential toolbox we must have to protect Earth from a devastating impact by an asteroid,” said Lindley Johnson, NASA’s Planetary Defense Officer. “This demonstrates we are no longer powerless to prevent this type of natural disaster. Coupled with enhanced capabilities to accelerate finding the remaining hazardous asteroid population by our next Planetary Defense mission, the Near-Earth Object (NEO) Surveyor, a DART successor could provide what we need to save the day.”

Not long ago we had a discussion here about this mission, I'm still very skeptical about the effective reach of the project to be honest. Sure, we hit an asteroid, but that's not a great news either, since Rosetta and Philae already managed something similar over 6 years ago. As far as I understood, even if they are already checking about the effectiveness of the impact using telescopes from Earth and orbit, the real extent of the success will only be validated with the Hera Mission, in four years from today.

To me, there's way too much enthusiasm about this whole project, and my reason is simple: awareness of the threat, coupled by actual effectiveness of the method. As far as our knowledge goes, there are two kind of threats we have to look upon: smaller, closer asteroid that can hit with almost zero forewarning and cause local wreckage, and very large comets (I mean, VERY large, in the order of tens or hundreds of kilometers, Hale-Bopp was 60 km wide, just saying), that can potentially cause a mass extinction event. Everything in between is being mapped already, and none of them really represents a threat in any foreseeable short term.

So, from one side, we have smaller objects with which this technique could be effective, but that we can't prevent at all, from the other we have very large objects that we will be aware of months (possibly even a year) in advance as they approach the inner solar system from the Oort cloud, but that, looking at their possible sizes, would be very much invulnerable to this technique.

As I said already, we are hundreds of years far from when we will be effectively able to defend ourselves from this kind of threats.

[skh1]

A very good survey of the subject:

Astronomy - YouTube

[Pontifex Maximus]

Not trying to be a dick - ​ I clicked and nothing worked. Do we have some alternatives?

[skh1]

What I was trying to link to was the PBS CrashCourse Astronomy play list

Does this link provide any joy?

CrashCourse - YouTube

(Scroll down to Physical Science where one will find Astronomy.)