ATERRA Commences Drilling at the Totora Copper-Gold Project, Chile

Toronto, March 25, 2026 - ATERRA Metals Inc. (CSE: ATC) (OTCQB: CSSCF) ("ATERRA") is pleased to announce that it has commenced a 3,000 metre ("m") Phase I drill program on its 1,811-hectare Totora Copper-Gold Project, located in Chile's Region III, 60 kilometers south of Vallenar. The Totora Project hosts four near-surface, copper-gold porphyries with the Phase I drill program focusing on the Totora and Frontera Deposit porphyries.

Commenting on the start of the drill program, Carl Hansen, CEO of ATERRA noted: "Now that our geological team has completed re-logging the majority of the historical drill core from the Totora Project, we have gained a more fulsome understanding of the relationship between copper-gold grades and geology (lithologies, alteration and structure). Based upon our review, we have designed a drill program that prioritizes: 1) the confirmation of the historical drill results; and 2) increasing the size of the copper-gold porphyries. Our goal is to publish a resource estimate during the third quarter of 2026 integrating our Phase I drill assay results with the significant historical drilling completed on the Totora Project over the past 15 years."

At the Totora porphyry, a 2,500 m reverse circulation drill program is underway adding to the 10,000 m of historical drilling which outlined a copper-gold porphyry system (see figure 1) along a strike length of over 800 m extending from surface to depths of up to 500 metres downhole. Historical drill results from the Totora porphyry include 142 m grading 0.58% copper equivalent ("CuEq") (0.47% copper and 0.17 grams per tonne gold) with a 72 m interval grading 0.83% CuEq (0.64% copper and 0.26 grams per tonne gold) from drill hole DDHTP-02.

Upon completion of the Totora porphyry drilling, ATERRA will undertake approximately 500 m of diamond drilling into the Frontera Deposit to confirm historical drilling results in preparation for the updated resource estimate. The Frontera Deposit hosts historical resources of:

For further information on the Totora Copper-Gold Project, including the Frontera Deposit and Totora, Clinton and Algarrobilla copper-gold porphyries, see ATERRA's previous press releases dated November 20, 2025 and February 3, 2026.

Figure 1 - Totora Cu/Au Porphyry - Geology and Historical Drill Plan

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Angie Property

Considering ATERRA's focus on its Totora Copper-Gold Project, the Angie Property option agreement has been terminated.

NI 43-101 Disclosure

Qualified Person: As defined by National Instrument 43-101 ("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 N° 515, in Chile, and registered in the Colegio de Geólogos de Chile under 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).

Regulatory requirements for disclosure of CuEq grade estimates require an estimation of metallurgical recoveries in the situation where no metallurgical testwork has been completed. ATERRA estimates copper recoveries of 85% and gold recoveries of 85%. It is important to note the actual recoveries will likely vary from those used in the estimation of the CuEq grades.

Historical Results: ATERRA has not undertaken any independent investigation of any historical results from the Totora Project nor has it verified the underlying technical basis for the historical resources and drilling results. The reader is cautioned against relying on the accuracy of the historical results presented; however, ATERRA considers all historical results relevant as those results will be used as a guide to plan future exploration programs: ATERRA considers the data to be reliable for these purposes.

About ATERRA Metals Inc.

ATERRA is a mineral exploration company focused on exploration opportunities in Chile. ATERRA's team of successful exploration professionals are dedicated to the discovery of mineral deposits that can be progressed into economically viable development projects creating value for all stakeholders.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This news release contains forward-looking statements, including predictions, projections and forecasts. Forward-looking statements include, but are not limited to: plans for the evaluation of exploration properties; the success of evaluation plans; the success of exploration activities; mine development prospects; and, potential for future metals production. Often, but not always, forward-looking statements can be identified by the use of words such as "plans", "planning", "expects" or "does not expect", "focus is to", "continues", "scheduled", "estimates", "forecasts", "objectives", "intends", "potential", "anticipates", "does not anticipate", or describes a "goal", or variation of such words and phrases or state that certain actions, events or results "may", "could", "would", "might", or "will" be taken, occur or be achieved.

Forward-looking statements involve known and unknown risks, future events, conditions, uncertainties and other factors which may cause the actual results, performance or achievements to be materially different from any future results, prediction, projection, forecast, performance or achievements expressed or implied by the forward-looking statements. Such factors include, among others: the successful completion of entering into option agreements with the Properties vendors, entering into agreements under the terms presented in this press release, the successful acquisition of exploration projects; changes in economic parameters and assumptions; all aspects related to the timing of exploration activities and receipt of exploration results; the interpretation and actual results of current exploration activities; changes in project or exploration parameters as plans continue to be refined; the results of regulatory and permitting processes; future metals price; possible variations in grade or recovery rates; failure of equipment or processes to operate as anticipated; labour disputes and other risks of the mining industry; the results of economic and technical studies; delays in obtaining governmental approvals or financing or in the completion of exploration; as well as those factors disclosed in ATERRA's publicly filed documents.

Although ATERRA has attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking statements, there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. There can be no assurance that forward-looking statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements.

Neither the Canadian Securities Exchange nor its regulation services provider has reviewed or accepts responsibility for the adequacy or accuracy of the content of this news release.

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