This week in science

NASA Perseverance Mars depot and more: Understand the world through 7 images

NASA

NASA

NASA’s Perseverance rover started building a crucial backup on Mars the week of December 21–28, as researchers found a new earliest example of Stone Age technology in the Americas.

Here are the week’s biggest science stories, told in 7 stunning images

© Jesse Delia

7. Mammals on the menu

Alex Dececci

December 21

Researchers found the remains of a small mammal preserved in the gut of a fossilized Cretaceous-era Microraptor zhaoianus. It’s the first evidence that the genus ate mammals, and one of very few examples showing mammals in any dinosaur’s diet.

Alex Dececci

6. Ready for pickup

NASA/JPL-Caltech/MSSS

December 21

NASA’s Perseverance rover deposited the first of 10 rock samples it will leave in a depot in the Three Forks region of Mars. Housed in titanium tubes, the samples provide a backup to be retrieved later if Perseverance can’t return its samples to Earth.

NASA/JPL-Caltech/MSSS

5. Now you see them...

Junjie Yao, Duke University

December 22

Researchers determined glassfrogs are able to become transparent by concealing nearly 90 percent of the red blood cells in their body inside their liver. They made the discovery using a non-invasive imaging technique that scans the body using soundwaves, as glassfrogs don’t become transparent when they’re stressed or sedated.

Junjie Yao, Duke University

4. ISS upgrade

NASA

December 22

Astronauts Josh Cassada and Frank Rubio installed the ISS’ fourth Roll-Out Solar Array in a seven-hour spacewalk. The operation to upgrade the space station’s power supply was delayed from earlier in the week to avoid debris from a Roscosmos rocket.

NASA

3. Deep breaths

© Courtesy of Michael T. Raissig

December 23

Researchers discovered two proteins that develop on either side of certain cells in grass, telling the plant where to develop “helper cells” that enable its respiratory pores to breathe. The study was focused solely on grass’ development, but could help scientists study other crops’ climate change resilience.

© Courtesy of Michael T. Raissig

2. Get to the point

Loren Davis

December 23

Archaeologists discovered the oldest projectile points ever found in the Americas, dating to around 15,700 years ago. The stone weapons — found on Nimíipuu land where Cooper’s Ferry, Idaho, now sits — are 3,000 years older than the previous earliest examples.

Loren Davis

1. Helping and hurting

Weill Cornell Medicine

December 28

Researchers discovered an enzyme that protects against viruses may also be responsible for driving cancer cell evolution. The APOBEC3G enzyme leads to more mutations in bladder cancer, and therapies targeting it could lead to future treatments.

Weill Cornell Medicine