Getting To Mars: What It’ll Take

Squishy physics!

How physicists see other fields:

Biology: squishy physics

Geology: slow physics

Computer Science: virtual physics

Psychology: people physics

Chemistry: impure physics

Math: physics without units

Elevated walkway and visitor centre added to 12th century abbey ruins by Binario Architectes »

Really? You’re really going to say this? 

First off: see this? 

This is my masters’ degree in anthropology. I’d show you my BA, but it’s at my parents’ house. I’m three and a half years into a PhD in physical anthropology. I’ve been employed to do physical anthropology at one of the world’s best natural history museums. My area of study? Teeth and diets. I’m not here to argue veganism or vegetarianism, I’m here to tell you, point by point, why you’re devastatingly misinformed about our place in the primate family tree, along with my peer-reviewed sources behind the jump. I know we live in a “post-truth” society so maybe being presented with the overwhelming consensus of the scientists who currently work with this material is meaningless to you, and honestly, this probably isn’t going to make a bit of difference for you, but I can’t let this slide. Not in this house built on blood and honor. And teeth.  

1. The evidence for being closely related to chimpanzees is vast and well-understood thanks to advances in DNA analysis. We share a huge amount of DNA with them, and not just repeating patterns in non-coding DNA. We have numerous genes that are identical and likely diverged around 7 million years ago, when Sahelanthropus tschadensis was roaming the earth. S. tschadensis was a woodland species with basal ape and basal human-line traits. The most notable was the positioning of the foramen magnum towards the central base of the skull and not emerging from the back suggests bipedality. This, along with other traits such as small canines worn at the tip, which implies a reduced or absent C/P3 honing complex (the diastema), suggests that this is actually a basal trait and the pronounced diastema we see in other species was a trait that came later. But more on that later- back to chimps and what we mean by sharing DNA. Our chromosomes and chimp chromosomes are structured far more like each other than other mammals. Furthermore, the genes located on these chromosomes are very similar. Chromosome 2, for instance, is nearly identical to two chimpanzee chromosomes. (Chromosome 2 in humans, Neanderthals, and Denisovans is different from Chromosome 2 found in apes and is actually the remnant of an ancient mutation where Chromosome 2 and 3 merged- you can see that from its vestigial centromeres and the genes found on it. We can’t get DNA from fossil material, but Neanderthal and Denisovan subfossils have demonstrated that this reduced chromosome count- we have one fewer pair than apes- is a typical trait of the Homo genus). Here’s a side by side comparison of Human and chimpanzee chromosomes. 

Gene coding regions are colored- bands at the same place mean that there’s two identical genes at that locus. Our similarities to lemurs, on the other hand, aren’t on homologous chromosomes. We have similar coding around the centromeres but the genes express themselves differently. The structure of non-ape primate genes is also significantly different; when the first chromosomal comparisons were done between humans and lemurs back in the 1990s, it was discovered that lemurs have much more highly-concentrated heterochromatin at their centromeres, whereas the structure of human and chimpanzee centromeres is similar. The major differences in chimp and human DNA are in the noncoding regions; most of our genes have identical structures. 

2.  All primates evolved from a lemur-like organism, not just humans. Here’s one of them. I’ve seen her in person. Pretty cool, huh?

Her name is Ida and she’s a member of the genus Darwinius. But that’s just like saying all primates evolved from something that was basically a tree shrew- which is also true. See, one of the main points of evolution is that organisms are continually changing throughout time. We didn’t jump from lemur-like organism to human; changes were slow and gradual and the lineage isn’t really a straight tree. The fossil species we have and know lead to different lines branching out. Some things died off, some things flourished. Heck, look at the Miocene- twelve million years ago, there were hundreds of ape species. Now there’s twenty-three. (Sixteen gibbons, two chimp species, two gorilla species, two orangutan species, and one human species. There’s also some subspecies of gorilla and gibbon, but I’m only counting the primary species.) It’s hard to trace things back, but saying that we evolved from lemur-like species is obtuse and obfuscates the real point, which is that Homo and Pan descended from a relatively recent-in-the-grand-scheme-of-things common ancestor. 

3. Our dentition is unique to the extant primates, but not australopithecines. Our teeth look very much like other members of the genus Homo, the extinct ones, as well as many of the australopithecines. We also have very similar enamel proportions to gracile australopithecines; apes have much thinner enamel overall.

But what did australopithecines eat?

Everything. We know they were eating fruits and nuts based on microwear analysis and strontium analysis, but we also know they were eating meat- and in pretty decent quantity, too. We’ve found all kinds of butchering sites dating back millions of years and in association with Australopithecus garhi, the earliest tool user, but we can also see this in tapeworm evolution. There’s many, many species of tapeworm in several genera. But three of them, in the genus Taenia, are only found in humans. And these species diverged from… carnivore tapeworms. Their closest relatives infect African carnivores like hyenas and wild dogs. 

Tapeworms that are adapted to the specific gut of their host species need a certain environment, as well as a specific cycle of infection so that it can reproduce. A tapeworm that infects hyenas is going to be less successful if it somehow makes the jump to a horse. But if the hyena tapeworm was able to adapt to our gut, that suggests that our stomach was hospitable enough for them chemically to survive- which brings me to the intestines.

4. Our intestines are also unique. Yes, we have longer intestines than carnivores, but we also don’t have cecums like herbivores. We are omnivores and that means we still needed to retain the ability to digest plants. 

The key to being omnivores is omni. All. I’m not saying we should only be eating meat, I’m saying our ancestors ate a varied diet that included all kinds of things. If we weren’t omnivores, why would we have lost the cecum’s function? Why is the human appendix only a reservoir for the lymphatic system, as it is in carnivores? The cecum is an extremely important organ in herbivores, as it houses the bacteria needed to break down cellulose and fully utilize fiber from leaves. But we don’t have that. Instead, we compensate with a long gut. Our ancestors absolutely did eat fruits and nuts and berries, but they also ate other stuff. Like scavenged carcasses and bugs and probably anything they could fit in their mouths. Which- actually, primate mouths are interesting. Humans and chimpanzees have enclosed oral cavities, thick tongues, and jaw angles much more like herbivores than carnivores- suggesting a herbivorous ancestor. That’s not something I’m arguing against at all. But again, we have adaptations for eating meat and processing animal protein because we are an extremely opportunistic species. 

5. Our canines are true canines. First, semantics: having a diastema does not canine teeth make. We refer to the canine teeth by position- even herbivores, like horses, have them. They’re the teeth that come right after the incisors. All heterodonts have the potential same basic tooth types- incisors, canines, premolars, molars- in various combinations and arrangements. Some species don’t have one type of teeth, others don’t have any- but it’s silly to say that the canine teeth aren’t canine teeth just because they don’t serve the same function as a gorilla’s or a bear’s or some other animal’s. It’s basic derived versus primitive characteristics. 

Now that we’ve got semantics out of the way, let’s talk about that diastema. The lost diastema is a derived trait, which means that our ancestors had it and we lost it over time. All other extant non-Homo primates have a canine diastema. All of them. However, when you look at australopithecines, we see that many of them either don’t have it or have it in a reduced capacity. At the earliest known hominin site, Lukeino, we see Orrorin tugenensis with reduced canines compared to ape fossils and modern apes- and… you do know that apes don’t use their canines for eating meat, right? Like, primate canines serve a very different purpose than carnivorans’ canines. It’s suggested that the large canines are for social display moreso than anything dietary- bigger, more threatening teeth are useful if you’re a gorilla or chimpanzee fighting to the top of your group’s social structure. 

I’m going to refer you to a blog post written by Dr. John Hawks, a good friend of my advisor and generally a pretty cool guy. He’s got a nice writeup on the evolution of hominin teeth and how the human line’s teeth have changed through time. 

Also, of course our teeth are going to be smaller. When we compare archaic Homo sapiens fossils to modern skeletons, their teeth and jaws are much more robust. This is likely related to the introduction of soft foods- and by soft, I mean cooked grain mush- to the diet around the time of domestication, right before the population explosion that happened about 10k years ago. In general, post-domestication human jaws are much smaller and more crowded than any other humans and hominins that came before.

6: Neanderthals did die out, but not in a catastrophic event like we think of with dinosaurs. While there are no living Neanderthals today that we would classify as Homo neanderthalensis, there is plenty of evidence that we interbred and likely outcompeted them as a species due to our overwhelmingly large population size (hypothesized based on number and locations of remains found). While there’s only a small percentage of Neanderthal mitochondrial DNA lines in human populations today, it’s quite likely we lost a lot of that due to genetic drift and population migration- Neanderthals, after all, had a much more limited range than Homo sapiens sapiens. Their eventual extinction is a mosaic of events- outcompetition plus assimilation. The line between Homo sapiens sapiens and Homo neanderthalensis/Homo sapiens neanderthalensis is blurry- there’s some physical anthropologists who actually think we should be including them within our species as a subspecies- but they are extinct in that the specific subset of hominins with distinct karyotypes and potential phenotypes no longer exists.

And if you don’t know, now you know.

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Mission Possible: Redirecting an Asteroid

As part of our Asteroid Redirect Mission (ARM), we plan to send a robotic spacecraft to an asteroid tens of millions of miles away from Earth, capture a multi-ton boulder and bring it to an orbit near the moon for future crew exploration.

This mission to visit a large near-Earth asteroid is part of our plan to advance the new technologies and spaceflight experience needed for a human mission to the Martian system in the 2030s.

How exactly will it work?

The robotic spacecraft, powered by the most advanced solar electric propulsion system, will travel for about 18 months to the target asteroid.

After the spacecraft arrives and the multi-ton boulder is collected from the surface, the spacecraft will hover near the asteroid to create a gravitational attraction that will slightly change the asteroid’s trajectory.

After the enhanced gravity tractor demonstration is compete, the robotic vehicle will deliver the boulder into a stable orbit near the moon. During the transit, the boulder will be further imaged and studied by the spacecraft.

Astronauts aboard the Orion spacecraft will launch on the Space Launch System rocket to explore the returned boulder.

Orion will dock with the robotic vehicle that still has the boulder in its grasp. 

While docked, two crew members on spacewalks will explore the boulder and collect samples to bring back to Earth for further study.

The astronauts and collected samples will return to Earth in the Orion spacecraft.

How will ARM help us send humans to Mars in the 2030s?

This mission will demonstrate future Mars-level exploration missions closer to home and will fly a mission with technologies and real life operational constraints that we’ll encounter on the way to the Red Planet. A few of the capabilities it will help us test include: 

Solar Electric Propulsion – Using advanced Solar Electric Propulsion (SEP) technologies is an important part of future missions to send larger payloads into deep space and to the Mars system. Unlike chemical propulsion, which uses combustion and a nozzle to generate thrust, SEP uses electricity from solar arrays to create electromagnetic fields to accelerate and expel charged atoms (ions) to create a very low thrust with a very efficient use of propellant.

Trajectory and Navigation – When we move the massive asteroid boulder using low-thrust propulsion and leveraging the gravity fields of Earth and the moon, we’ll validate critical technologies for the future Mars missions. 

Advances in Spacesuits – Spacesuits designed to operate in deep space and for the Mars surface will require upgrades to the portable life support system (PLSS). We are working on advanced PLSS that will protect astronauts on Mars or in deep space by improving carbon dioxide removal, humidity control and oxygen regulation. We are also improving mobility by evaluating advances in gloves to improve thermal capacity and dexterity. 

Sample Collection and Containment Techniques – This experience will help us prepare to return samples from Mars through the development of new techniques for safe sample collection and containment. These techniques will ensure that humans do not contaminate the samples with microbes from Earth, while protecting our planet from any potential hazards in the samples that are returned. 

Rendezvous and Docking Capabilities – Future human missions to Mars will require new capabilities to rendezvous and dock spacecraft in deep space. We will advance the current system we’ve developed with the international partners aboard the International Space Station. 

Moving from spaceflight a couple hundred miles off Earth to the proving ground environment (40,000 miles beyond the moon) will allow us to start accumulating experience farther than humans have ever traveled in space.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

science news: another incredibly smart and driven woman who discovered really important things just died without receiving recognition in her lifetime for any of her groundbreaking crucial work after decades of brutally unfair sexism click through for even more in depth accounts of the monstrous amount of sexist bullshit she had to put up with every single day of her goddamn life

science news: girls today are hesitant to go into STEM fields for some reason

A great visualization of where the stratosphere is thanks to Mt. Etna.

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Vote down ballot - the presidency isn't the only office of importance!

Time for another political essay. If you’re not an American citizen or able to vote in this upcoming election, my apologies.

I make no secret that I fucking despise Donald Trump. I actually like Hillary Clinton, which seems to be a weird rarity considering the amount of good work she’s done and the fact that all of the bad press about her is the result of the Republicans trying (and failing) to tear her and her husband down for thirty years.

Trump is now trailing far behind Clinton, which I consider a cause for celebration. But it is NOT a cause for complacency.

The biggest landslide election in US history was the election of Warren G. Harding in 1920, when Harding won with about 60% of the vote to his opponent’s 34.2%.

Some polls are reporting Trump with as little as 35% of the popular vote right now.

If turnout is large enough and loud enough, we can make Donald Trump the least supported major candidate in US history. Since the recording of him bragging about sexual assault came out, he has turned to dragging the whole election into the mud by striking back at Bill Clinton’s affairs; the usual goal of that kind of tactic is to drive down voter turnout. Trump’s band of Redcaps is pretty much guaranteed to vote, so they figure if they reduce turnout enough, they’ll win.

I want their plan to fail. I want their plan to fail so fucking spectacularly that NO ONE will dare to run for President on a platform of thinly-veiled fascism again.

The Republicans thought the House of Representatives was safe this year. In 2010, they gerrymandered the shit out of district lines to keep the House safe for them for at least ten years. But there’s a problem with gerrymandering: if the demographics shift unexpectedly between censuses, then suddenly a lot of districts wind up flipping against the party that the gerrymandering was meant to support. And Donald Trump is driving away the Republicans’ most secure core of voters, the evangelicals. And as I’ve said before: Congress is MORE important than the presidency.

If turnout is strong enough, and if people vote down ballot, the possibility exists for a massive upset. A Democratic presidency, a Democratic House, a Democratic Senate. They’re within our grasp. All you need to do, voters, is show up.

Motherfuckers don’t want you to vote. Young people, people of color, women, LGBTQ+ folks–they want you to be scared away, or to be convinced that voting doesn’t matter. They want your voice silenced. Don’t give the fuckers the satisfaction of letting it happen.

GO VOTE. VOTE DOWN-BALLOT. MAKE TRUMP THE BIGGEST LOSER IN US HISTORY.

IF YOU CAN’T BE BOTHERED TO VOTE OUT OF CONVICTION, THEN DO IT OUT OF SPITE.

This awesome plane-train hybrid could revolutionize transportation, but not for another 50 years    

Imagine a future where a plane lands at an airfield that doubles as a rail yard. The cabin — one of three that cling to the underbelly of the aircraft like a baby possum to its mother — detaches, is seamlessly transferred to a nearby train, and then continues its journey toward the city center. Your multi-seat trip (taxi-to-subway-to-airtrain) from home to hotel suddenly becomes a one-seat, hassle-free ride. That’s the aim of a consortium of Swiss researchers with the conceptual Clip-Air, a bold-looking plane-train hybrid that despite its high-minded possibilities, will probably never get made.

Surgeon Al-Zahrawi (936–1013 CE) from Cordoba in the Muslim kingdom of al-Andalus, was one of the most famous physicians of the middle ages. He invented many medical instruments, and wrote the first surgical textbook which included illustrations like the one above. It was not just a textbook, however. The Kitab al-Tasrif is a 30-chapter treatise on multiple areas of medicine, including surgery, dentistry, and childbirth.