Spend the day preparing supplies for tomorrow's return to Yucatán, Mexico, while preparing my classes, laboratories and the Space Imagery Center in Arizona for a brief absence.
I am eager to get to the Chicxulub scientific drilling project, where we will be recovering the first continuous core of rock from the 65-million-year-old Chicxulub asteroid impact crater. This crater - which is about 180km wide and could have been caused by an asteroid or comet up to 17km across - is linked to the dinosaurs' extinction. But we have a difficult task because the crater is buried beneath a kilometre of younger rock.
An undergraduate geosciences student who has agreed to help with the project joins me on the flight from Tucson to Mérida.
We arrive early evening at the Colonial Hotel near Independence Plaza. The city's central square is crowded with people enjoying the final night of carnival, but everyone is soon chased away by a spring shower.
After an early breakfast, we walk to the central plaza to watch a daily honour guard raise the nation's flag.
By 8am we are on the road, driving to the drilling site near the Hacienda de Yaxcopoil. We arrive as a new core is being pulled to the surface.
I discuss the status of the project with the drilling operations manager before visiting Chicxulub Pueblo, the village that gave its name (meaning "tail of the devil") to the crater and is located above the crater's centre.
At the University of Yucatán, we study cores from the crater, trying to tease out clues about the dinosaurs' demise.
Later, I agree to take over the duties of the geology team on the night shift at the drilling site. Throughout the night we remove core from the ground, ecstatic to be getting a 100 per cent core recovery rate. It often emerges steaming after being pulled from a depth of 1.2km.
It is a spectacular star-filled night in the Yucatán, an area of tropical jungles, Maya ruins and modern agricultural sites. Occasionally, ground fog rolls through and eerily reflects lights around the drilling site.
Our relief arrives at 8am, but we stick around for a bit to watch the next core come to the surface before returning to our hotel.
I have now been awake for 28 hours. But after only a couple of hours'
sleep, we are on the move again, driving to the north edge of the Yucatán peninsula to take some background photographs.
On the way back, we stop at the core-processing lab. I re-examine some of the samples to try to determine what portions of the earth's crust were melted by the impact and how the melted material was redeposited in the crater.
Another early start as we arrive at Yaxcopoil a few minutes before 8am and begin to study the additional core as the drilling team pulls it up in 3m segments.
We are recovering a lot of anhydrite, which - when vaporised by the impact and injected into the atmosphere - may have been a severe blow to earth's climate. Our relief arrives at 8pm, and we return to Mérida for a much-needed bath and dinner.
The drilling project was scheduled to end today, so I have already made plans for my departure. Yesterday, however, money was found to continue the project for five more days. I need to return to my university teaching obligations, but my student will stay while the drilling team tries to reach a final depth of 1.5km.
Arriving at the Mérida airport early, I arrange to fly to Cancun in a small, low-flying plane so I can get a better look at the Yucatan from the air, particularly the ring of cenotes , beautiful circular springs carved from the limestone that decorate the rim of the crater.
From Cancún, I fly back to the States, eager to report the high quality of the rock core to the rest of my team.
David A. Kring is associate professor of planetary sciences at the lunar and planetary laboratory, University of Arizona.