Tens of thousands of people participated in the People's Climate March on Trump's 100th day in office.

Abstracts: Climate March, Animal Welfare, and More

• Trump’s 100th day in office was marked by the People’s Climate March, which drew tens of thousands of people to the streets of D.C. Hundreds of satellite marches were held in cities across the globe. (ABC News)

Tens of thousands of people participated in the People’s Climate March on Trump’s 100th day in office. Visual: Astrid Riecken/Getty Images

• People might one day build red brick houses on the Red Planet. An engineer has devised a way to fashion bricks from Martian soil with nothing but a hammer. (The Independent)

• In January, the U.S. Department of Agriculture removed a public database that contained animal welfare information from zoos, circuses, and labs. National Geographic submitted a Freedom of Information Act request to find out why, and received 1,700 blacked-out pages. (National Geographic)

• A group of German scientists discovered the DNA of ancient humans in cave dirt. This is the first time researchers have been able to study the genes of ancient peoples without having to unearthing fossils first. (New York Times)

• Researchers just crafted the first comprehensive map of the dark web — that shady corner of the internet that can only be accessed via special anonymizing software. They discovered that unlike the above-board internet where sites typically contain links to other sites, the vast majority of dark web sites are entirely isolated. (Science)

• Eleven people in Liberia have died of an unknown illness. Only Ebola has been ruled out so far, but medical officials do have one lead in the case of this mystery disease: all of the victims attended the same religious leader’s funeral. (The Guardian)

• A new study in Science shows that ancient domesticated horses were much more genetically diverse than their modern counterparts. (Science News)

• Anyone who needs a yellow fever shot in preparation for international travels should get one soon, as the U.S. supply of the vaccine is expected to run out by midsummer. (NPR)

• A partnership between the University of Southern California and Kingsley Manor Retirement Community in Los Angeles allows select students to live for free in the retirement home in exchange for teaching classes and assisting residents. With the demand for gerontologists growing, the immersive program aims to increase health care providers’ interest in the field and better prepare them to care for an aging population. (STAT)