ATERRA Metals Commences Preparation of Maiden Mineral Resource Estimate for the Totora Cu/Au Project

Toronto, Ontario--(Newsfile Corp. - August 6, 2026) - ATERRA Metals Inc. (CSE: ATC) (OTCQB: CSSCF) (" ATERRA " or the " Company ") is pleased to announce that it has commenced preparation of the Company's maiden independent Mineral Resource Estimate (" MRE ") for its Totora Cu/Au Project (" Totora " or the " Project ").

The maiden MRE will define Totora's initial mineral inventory and establish the technical foundation for future economic studies. ATERRA has engaged SRK Consulting (Chile) SpA (" SRK "), a leading international mining consultancy, to prepare the independent MRE. The Project is located in the Dos Amigos Mining District, 15 kilometres south of Tintina Mines' Domekyo Sulfuros development project (see Figure 1).

The MRE will be prepared in accordance with Canadian Securities Administrators' National Instrument 43-101 - Standards of Disclosure for Mineral Projects ("NI 43-101") and will incorporate the results from ATERRA's recently completed Phase I drill program together with historical drilling completed on the Project. The estimate will focus on the Company's three principal copper-gold porphyry systems - Frontera, Totora and Clinton - which collectively represent the most advanced exploration targets on the property. It is anticipated that the MRE will be available for release during September 2026.

Carl Hansen, Chief Executive Officer of ATERRA, commented: "Our objective is to establish the first independently verified mineral resource at Totora by integrating the results from a number of historical drill programs with our successful Phase I drilling. A maiden resource will provide investors with the first quantitative assessment of the scale of the Project and guide ATERRA's future exploration and development plans. This work marks an important step toward unlocking the value of the Totora Project."

Mr. Hansen continued: "Recent investments by multiple companies in the Dos Amigos Mining District underscore renewed industry interest in the region's copper-gold potential. We believe this increasing activity highlights the strategic position of the Totora Project within an emerging mining district."

Phase I Totora Drilling Highlights The Mineral Resource Estimate will incorporate the results of ATERRA's recently completed Phase I drill program at Totora, the highlights of which were previously disclosed in the Company's news release dated July 16, 2026. Selected drill highlights previously reported include: Frontera (AFROD01): 284 metres grading 0.64% CuEq (0.41% Cu & 0.27 g/t Au) from surface, including 180 metres grading 0.71% CuEq (0.48% Cu & 0.28 g/t Au); and Totora (ATOD01): 194 metres grading 0.41% CuEq (0.35% Cu & 0.11 g/t Au) from 254 metres downhole.

NI 43-101 Disclosure Qualified Person: As defined by NI 43-101 of the Canadian Securities Administrators, the "Qualified Person" for ATERRA Metals Inc. is Francisco Bravo, a resident of Santiago, Chile. As ATERRA's Chief Geologist, Mr. Bravo is considered "not independent" as the term is defined by NI 43-101. Mr. Bravo, a Public Registered Person for Reserves and Resources in Chile (N° 515) and registered with the Colegio de Geólogos de Chile (N° 725), has reviewed and approved the technical information contained in this press release.

Copper Equivalent Estimation: Copper equivalent ("CuEq") grades were estimated using a copper price of US$4.00 per pound and a gold price of US$3,500 per ounce (US$112.53 per gram). CuEq grades are estimated using the following formula: CuEq% = (((Au grade * 0.85 * 112.53) / 4.00 / 2,204.6) * 100) + (Cu grade * 0.85).