Written by Melissa Rice, Professor of Planetary Science at Western Washington University
This week, the Perseverance team faced a stubborn engineering challenge. After successfully collecting a core called “Green Gardens” from the “Tablelands” location, the rover struggled to seal the sample tube, despite multiple attempts. This isn’t entirely unprecedented — for a previous sample called “Mageik,” it took 40 days before being successfully sealed. The Green Gardens core is particularly exciting for our science team because it contains serpentine minerals, which may have formed billions of years ago when water interacted with rocks before the Jezero crater impact. On Earth, serpentine-rich environments can support microbial communities, making this sample particularly important to understanding ancient Mars’ potential for life.
The science team was torn with competing priorities: sealing up Green Gardens as quickly as possible vs. continuing to our next important science stop, “Broom Point.” Several options were considered: (1) stay put and focus on sealing, (2) start driving and keep trying to seal Green Gardens on the road, or (3) dump the Green Gardens sample from the tube and try extracting another core at Tablelands (this was the most drastic option). The science team went with (2), a dual-track strategy that would allow us to keep mission momentum while giving our engineers time to develop new approaches to the sealing challenge. The risk was that option (2) would keep the Green Gardens sample open for potentially a long time — depending on how obstinate the sample sealing would be — leaving the rock core exposed to the harsh conditions of Mars’ surface.
It was a trade that mission scientists were willing to make, and Perseverance has been making impressive progress down the west side of Jezero crater’s rim. With a downhill tilt there of 16 degrees, rover imagery is providing sweeping views of the landscape ahead toward Broom Point, where the rover will be tasked with studying the bright bedrock bands in the week to come.
And our optimistic approach paid off, because — voila! — our latest attempt to seal Green Gardens worked! The image above shows the seal successfully topping the sample tube. The next time the science team sees Green Gardens will be in a laboratory here on Earth, when we will finally learn what story the serpentine minerals have to tell. Until then, this sample’s lips are sealed, so to speak.
